INTRODUCTION — Striae distensae are a common form of dermal scarring that appear on the skin as erythematous, violaceous, or hypopigmented linear striations. Synonyms include the terms striae, stretch marks, and striae atrophicans. Striae gravidarum are striae distensae occurring secondary to pregnancy.
There are two main types of striae distensae: striae rubra and striae alba. Striae rubra are the earliest presentation of striae distensae and are characterized by an erythematous to violaceous color (picture 1A-C). Over time, striae rubra evolve into striae alba, which appear hypopigmented, atrophic, and scar-like (picture 2A-B). Common locations for striae distensae are the abdomen, breasts, medial upper arms, hips, lower back, buttocks, and thighs.
Although typically asymptomatic, striae distensae may be disfiguring and psychologically distressing to patients. Various topical and procedural modalities have been employed for the treatment of striae distensae (algorithm 1). (See 'Treatment' below and 'Prevention' below.)
The clinical features, diagnosis, and management of striae distensae will be reviewed here.
EPIDEMIOLOGY AND RISK FACTORS — Epidemiologic data on striae distensae in the general population are limited [1-11]. Reported incidences have ranged from as low as 11 percent in normal men to up to 88 percent in pregnant females [5,11]. Predisposing factors include pregnancy, adolescent age, drug exposure (eg, topical or systemic corticosteroids), underlying disease (eg, Cushing's syndrome), and surgery (eg, breast augmentation) [12,13]. A more extensive list of associated conditions is provided (table 1).
Studies specifically exploring risk factors for striae distensae secondary to pregnancy (striae gravidarum (picture 3A-B)) suggest that striae gravidarum occur more frequently in women with [3,5,6,14,15]:
●A family history of striae gravidarum
●Higher prepregnancy body mass index (BMI)
●Higher weight gain during pregnancy
●Higher birth weight and gestational age
●Multiple gestation pregnancies
●Lack of chronic diseases
Increased maternal age seems to protect against striae gravidarum, suggesting counterintuitive differences in stretching ability between older and younger skin . In a French series of 800 primiparas examined postpartum for striae gravidarum, 84 percent of 51 women under age 20 developed striae gravidarum compared with only 24 percent of 195 women age 30 or older (odds ratio 28.25, 95% CI 11.04-72.27) .
The findings of a study of 299 women in Poland suggest that the distribution of striae distensae prior to pregnancy may be an indicator of risk for the development of striae gravidarum . In the study, primiparous or multiparous women who reported striae distensae on the breasts prior to their most recent term delivery were more likely to report the development of striae gravidarum than patients who did not (71 versus 29 percent). In contrast, women who reported striae distensae on the thighs prior to pregnancy were less likely to report striae gravidarum than other women (23 versus 77 percent). An elevated risk for striae gravidarum is also proposed for women born prematurely . Further study is necessary to confirm these findings.
PATHOGENESIS — The pathogenesis of striae distensae is not well understood and is likely multifactorial. Physical factors resulting in increased tension on the skin, intrinsic alterations in skin structure or function, and hormonal factors may be involved:
●Physical factors – A role for mechanical stress on the skin is suggested by the observation that striae often develop in sites experiencing rapid increases in girth (as occurs in pregnancy), rapid weight gain, pubertal growth spurts, and exercise-induced muscle hypertrophy.
●Altered skin structure or function – Striae distensae do not develop in all skin sites subjected to mechanical stress or in all individuals. Therefore, specific characteristics of skin in affected areas may influence development. Reduced migration and proliferation of fibroblasts , reduced procollagen and fibronectin gene expression , marked disruption of the elastic fiber network , and the emergence of thin, disorganized, tropoelastin-rich fibrils  have been detected in biopsies of affected skin.
Genetic alterations in connective tissue may contribute to striae distensae. Striae distensae are a common finding in Marfan syndrome. (See "Genetics, clinical features, and diagnosis of Marfan syndrome and related disorders".)
●Hormonal factors – The common occurrence of striae distensae in pregnancy and Cushing's syndrome contributes to the theory that hormonal factors influence development of the condition (picture 1B). Potentially relevant observations include:
•Altered expression of hormone receptors, including increased expression of androgen and glucocorticoid receptors and reduced expression of estrogen receptors in the dermis of early striae distensae, have been detected when compared with perilesional skin and normal controls [21,22].
•Serum cortisol elevation leads to alterations in collagen and elastic fibers through increased protein catabolism . An example of this is seen in Cushing's syndrome, where increases in corticotrophin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), and subsequent increases in cortisol levels lead to generalized protein breakdown, causing skin and muscle atrophy and loss of bone. Cortisol increases free amino acids in serum by inhibiting collagen formation, decreasing amino acid uptake by muscle, and inhibiting protein synthesis .
•Lower serum levels of relaxin (a hormone that can decrease collagen production and increase collagen breakdown) are detected at 36 weeks gestation in women with striae gravidarum compared with women without this finding . It is proposed that the resulting reduced elasticity of connective tissue contributes to greater risk for elastic fiber disruption and striae formation .
CLINICAL MANIFESTATIONS — Striae distensae may initially appear as edematous striations that evolve to the red-to-purple, flat or atrophic plaques known as striae rubra (picture 1A-C). Striae rubra eventually progress to striae alba, hypopigmented, scar-like depressions with fine wrinkling (picture 2A-B). This progression often occurs over the course of 6 to 10 months . Striae alba persist indefinitely and may become more prominent with age as skin thins and loses additional elasticity. In patients with highly pigmented skin, striae distensae may also be dark gray to black (striae nigrae) or bluish (striae caerulea) [27,28].
Striae distensae usually occur in a symmetrical distribution. The striae are typically oriented along skin tension lines and are a few millimeters to 1 centimeter in diameter. Common locations for involvement are the abdomen, breasts, thighs, and buttocks . The lower back, calves, medial upper arms, and hips are additional frequent locations.
Striae gravidarum tend to develop in the second and third trimester of pregnancy and commonly occur on the abdomen, breast, or thighs (picture 3A-B). Patients with Cushing's syndrome may have particularly prominent and widely distributed striae. Striae distensae secondary to topical corticosteroid use often occur in intertriginous areas.
HISTOPATHOLOGY — The histopathologic findings of striae rubra and striae alba differ. Striae rubra exhibit flattening of the epidermis with loss of rete ridges. An inflammatory infiltrate with lymphocytes and histiocytes may be present in the dermis . The centers of early striae rubra may also show a reduction in normal collagen, elastin, and fibrillin content in the dermis, while thick, tortuous elastic fibers reside at the periphery [31,32]. Pathologic analysis of early, erythematous striae gravidarum reveals disorganized collagen fibrils that fail to form normal collagen bundles .
Electron microscopy may demonstrate mast cell degranulation, macrophage activation, and elastolysis in the mid-dermis .
Striae alba exhibit histopathology similar to that of an atrophic scar, with epidermal atrophy, loss of rete ridges, and thin dermal collagen bundles arranged parallel to the skin surface [34,35].
DIAGNOSIS — The diagnosis of striae distensae usually can be made based upon visual examination. Linear, atrophic plaques in susceptible sites (eg, abdomen, breasts, buttocks, thighs) are characteristic. A skin biopsy is not usually necessary.
The evaluation of patients with striae distensae should include questions to determine the most likely cause for striae development. We routinely inquire about common causes, including pregnancy, rapid weight gain or loss, rapid growth, bodybuilding exercise, and medications (particularly topical or systemic corticosteroids).
Patients with associated systemic signs or symptoms may require further evaluation to rule out an underlying medical condition. As examples, supraclavicular fat pads, skin atrophy, wide purplish striae, and proximal muscle weakness suggest Cushing's syndrome, and an unusual distribution of striae distensae in a tall patient with arachnodactyly and aortic abnormalities should raise suspicion for Marfan syndrome. A list of additional conditions to consider during the patient evaluation is provided (table 1). (See "Epidemiology and clinical manifestations of Cushing's syndrome" and "Genetics, clinical features, and diagnosis of Marfan syndrome and related disorders".)
DIFFERENTIAL DIAGNOSIS — Striae are usually easily recognized based upon the characteristic linear configuration and distribution, which limits the differential diagnosis. The major disorder in the differential diagnosis is linear focal elastosis (also known as elastotic striae).
Linear focal elastosis is an uncommon disorder characterized by the development of multiple raised, linear bands that are usually yellowish in color and horizontally arranged on the lower back (picture 4) . Biopsy may demonstrate aggregated or fragmented elastic fibers [36,37]. The etiology and pathogenesis is unclear. Linear focal elastosis may represent an excessive regenerative process of elastic fibers (ie, a keloidal repair of striae distensae) [37,38].
Occasionally, anetoderma, a disorder that presents with well-circumscribed, atrophic-appearing, depressed, wrinkled, flaccid, or pouch-like protrusions, may enter the differential diagnosis (picture 5) . Anetoderma lacks the long, linear, atrophic bands characteristic of striae distensae. Individual areas of anetoderma are typically 1 to 2 cm in diameter. Anetoderma may occur as a primary skin disease or as a result of a preceding inflammatory process.
In pregnant women, the development of erythematous, very pruritic papules or plaques within striae (particularly on the abdomen) should raise suspicion for pruritic urticarial papules and plaques of pregnancy (PUPPP) (picture 6). (See "Dermatoses of pregnancy", section on 'Polymorphic eruption of pregnancy'.)
TREATMENT — Striae distensae are non-life-threatening and asymptomatic but can have a negative impact on quality of life [40,41]. Therapeutic interventions aim to improve the appearance of affected skin through reducing color or texture differences between striae and adjacent normal skin.
General principles — Treatment of striae distensae can be challenging, as no therapy induces complete resolution. Moreover, a paucity of high-quality trials and a lack of a reliable, validated, and widely accepted tools to assess striae severity and responses to treatment preclude definitive guidelines for the best approach to treatment [42,43].
The therapeutic approach should involve consideration of the clinical findings (striae rubra versus striae alba) as well as patient preferences (algorithm 1). Common initial interventions are pulsed dye lasers, fractional lasers, microneedling, microneedling with radiofrequency (RF microneedling), and topical retinoids.
It is important to carefully counsel patients prior to proceeding with therapy. Treatment results are unpredictable and vary widely in patients treated with similar regimens. Potential adverse effects should also be thoroughly reviewed with patients.
Pregnant patients — Treatment of striae distensae in pregnant patients is usually deferred until after delivery because of concerns or insufficient data regarding the effects of various therapies on the fetus. In particular, topical retinoid therapy is avoided during pregnancy. The prevention of striae distensae in pregnant women is discussed separately. (See 'Prevention' below.)
Striae rubra — Pulsed dye laser therapy is a common first-line treatment for striae rubra (algorithm 1). Treatment may both improve erythema and exert beneficial effects on dermal collagen.
Topical tretinoin can stimulate collagen synthesis and is an alternative for patients with striae rubra who are unable or unwilling to proceed with laser therapy. However, adherence to several months of daily application is usually required, and skin irritation is common. We have had the most success with topical tretinoin in adolescents treated soon after the onset of striae rubra.
Pulsed dye lasers — Pulsed dye lasers target hemoglobin, a characteristic that is advantageous for reducing erythema in striae distensae. Pulsed dye lasers may also induce modest improvement in skin texture, as evidenced by an increase in dermal collagen and elastin content  (see "Laser and light therapy for cutaneous vascular lesions", section on 'Pulsed dye laser'):
●Administration – Pulsed dye laser therapy is usually performed every four to six weeks. Nonpurpuric settings with pulse durations of 6 to 10 milliseconds and fluence settings of 6 to 7.5 J/cm2 are often utilized. Treatment is continued until progressive improvement ceases or a satisfactory response is achieved. A typical course consists of five to six treatments. Treatment may be discontinued if there is no evidence of response after three treatments.
Fractional laser therapy is sometimes performed after a series of pulsed dye laser treatments in an attempt to achieve additional improvement. Our experience suggests that combining pulsed dye laser therapy with same-day fractional laser therapy as initial treatment may also be beneficial. (See 'Fractional lasers' below.)
●Recovery and complications – Potential side effects include purpura, postinflammatory hyperpigmentation, blistering, and rarely, scarring. Treatment of patients with skin phototypes IV to VI (table 2) should be avoided or performed with caution because of risk for longstanding dyspigmentation. We typically treat these patients with microneedling or RF microneedling. (See 'Microneedling devices' below.)
●Efficacy – Data from uncontrolled and comparative studies suggest that treatment with a 585 nm or 595 nm pulsed dye laser can yield mild to moderate improvements in striae distensae [44-49]. Striae rubra may be more likely to exhibit improvement after pulsed dye laser therapy than striae alba; however, both types of striae may improve after a series of treatments (picture 7) [45,47,49].
Topical retinoids — Topical retinoid therapy is an alternative to laser therapy. The mechanism of topical retinoid therapy may relate to the affinity of these drugs for fibroblasts and the induction of collagen synthesis [50-52].
Topical tretinoin is considered the retinoid of choice for striae distensae. It is often assumed that other topical retinoids (eg, adapalene, tazarotene) can be effective ; however, data to confirm similar efficacy are lacking:
●Administration – A very thin layer of tretinoin is applied once nightly to the affected areas for several months. We typically use tretinoin 0.1% cream. Initial improvement may be noted within the first two months of treatment [51,54].
In patients who demonstrate improvement in striae, treatment may be continued until a satisfactory response has been achieved or progressive improvement ceases. If there is no improvement after three to six months, treatment can be discontinued (algorithm 1).
Retinoid dermatitis characterized by erythema and scaling is a common side effect and may lead to postinflammatory hyperpigmentation, particularly in patients with skin phototypes IV to VI (table 2). Retinoid dermatitis can usually be managed with emollients. If necessary, the frequency of retinoid application can be temporarily decreased. If tretinoin 0.1% cannot be tolerated, a topical retinoid that may be less likely to induce skin irritation may be used, such as tretinoin 0.05% emollient cream, tretinoin 0.05% lotion, adapalene 0.1% gel or cream, or adapalene 0.3% gel.
Use of tretinoin or other topical retinoids is not recommended during pregnancy.
●Efficacy – Efficacy of topical tretinoin was demonstrated in a randomized, vehicle-controlled trial in which 26 patients with striae rubra were randomly assigned to once-nightly application of tretinoin 0.1% cream or vehicle to affected areas for 24 weeks . Of the 10 patients in the tretinoin group who completed the trial, four had marked improvement, four had improvement, and two had no response after six months of treatment. In the vehicle group, none of 12 patients had marked improvement, one had improvement, and the remainder had no improvement or worsening of striae. The common occurrence of retinoid-induced dermatitis could have influenced blinding of the trial.
Efficacy for striae rubra is also supported by a 16-week, randomized, open-label study that compared tretinoin 0.05% cream with superficial dermabrasion in 32 women with striae rubra  and a 12-week, open-label study that associated treatment with tretinoin 0.1% cream and petrolatum with reductions in striae in 26 women with striae gravidarum who began treatment soon after delivery . A randomized trial that found a failure of topical tretinoin to improve abdominal striae distensae utilized a lower concentration of tretinoin (0.025% cream) and did not restrict the study population to patients with striae rubra . (See 'Superficial dermabrasion' below.)
Striae alba — Preferred initial treatments for striae alba are fractional laser therapy and microneedling (algorithm 1). Many experts combine microneedling with the delivery of radiofrequency energy (RF microneedling) with the goal of increasing efficacy of microneedling. (See "Principles of laser and intense pulsed light for cutaneous lesions", section on 'Fractionated lasers'.)
Fractional laser therapy involves the delivery of narrow columns of laser light to the skin, resulting in vertical zones of thermal damage and the induction of wound healing processes that lead to improvements in dyspigmentation and the texture of skin. Both ablative and nonablative fractional lasers are effective options for striae alba; ablative therapy may require fewer treatments than nonablative therapy but is associated with longer recovery periods and greater risk for adverse events.
Microneedling alone is a lower cost intervention that injures columns of skin through the delivery of a stamped array of thin needles into the skin, stimulating neocollagenesis. RF microneedling, akin to the cost of nonablative resurfacing lasers, combines microneedling with the application of heat to the dermis and induces tissue remodeling and neocollagenesis. Microneedling has a lower risk for side effects, such as dyspigmentation and scarring, compared with ablative and nonablative laser therapy. Therefore, for patients with the highest risk for dyspigmentation (skin phototypes IV to VI (table 2)), RF microneedling is our preferred initial therapy. (See 'Microneedling devices' below.)
Although we will attempt topical tretinoin therapy in patients who are unable or unwilling to undergo fractional laser therapy or RF microneedling, benefit of topical tretinoin for striae alba is uncertain. Patients should be counseled accordingly.
Fractional lasers — Nonablative and ablative fractional lasers may improve skin texture and dyspigmentation in striae distensae (figure 1). Fractional lasers emit narrow columns of infrared light, resulting in numerous narrow columns of coagulated or ablated skin, called microthermal zones. The wound healing processes that follow skin injury contribute to improvements.
Selection — Both ablative and nonablative fractional lasers are appropriate and effective options for striae alba. Consideration of factors such as risk for complications, expected recovery time, and number of treatments required influences selection between these therapies. Ablative fractional lasers induce greater injury to the skin than nonablative lasers and may require fewer treatments to achieve a similar effect. However, ablative therapy is associated with a longer recovery period and greater potential for complications. In general, we prefer to treat with nonablative fractional lasers because of the lower risk for complications.
The relative efficacy of nonablative and ablative fractional lasers was evaluated in a split-abdomen trial that compared three treatments with a 1550 nm nonablative fractional laser and an ablative fractional carbon dioxide (CO2) laser. Although the trial did not find a statistically significant difference in effect on postpregnancy abdominal striae alba (good or fair improvement in 8 of 22 sites [36 percent] versus 12 of 22 sites [55 percent], respectively), a larger study with a longer follow-up period may have demonstrated a difference . Responses were assessed only four weeks after treatment, and tissue remodeling resulting in increased epidermal thickness, dermal thickness, and collagen and elastin fiber deposition often continues for months after fractional laser therapy [58-60].
Nonablative fractional lasers — Nonablative fractional laser therapy for striae distensae is typically performed with 1550 nm fractional lasers:
●Administration – The ideal regimen for nonablative fractional laser therapy for striae distensae is unknown. We typically administer a series of three to six once-monthly treatment sessions in an attempt to maximize efficacy. Treatment is administered in the office with topical anesthesia and forced air cooling for comfort. Energy and density settings should be reduced in patients with skin phototypes V or VI to minimize risk for postinflammatory hyperpigmentation. Clinical improvement may continue for three to six months after cessation of treatment.
●Recovery and complications – Post-treatment sunburn-like erythema, edema, and rough desquamation occurs for one to two weeks after treatment on nonfacial sites. Additional potential side effects include postinflammatory hyperpigmentation and prolonged erythema or edema. Patients with skin phototypes IV to VI (table 2) are at increased risk for dyspigmentation after laser treatment. Strict adherence to sun-protective measures is recommended after laser therapy to reduce risk for dyspigmentation.
Dermatitis, ulceration, impetigo, and purpura are rare complications .
●Efficacy – Uncontrolled studies document modest to marked benefit in the appearance of striae distensae after nonablative fractional laser therapy (picture 8A-B). Although some degree of improvement appears to be common, very good or excellent responses seem to occur less frequently. Beneficial responses to 1540 nm, 1550 nm, 1565 nm, and 1340 nm devices have been reported [58-66]. Treatment regimens vary.
Whether striae rubra or striae alba are more likely to respond to nonablative fractional laser resurfacing is unclear. Studies have reported responses in both types of striae distensae [60,62] as well as more favorable responses in patients with striae alba . In a prospective study of 22 women given two treatment sessions with a 1550 nm fractional laser for striae distensae secondary to pregnancy or weight gain, marked clinical improvement occurred in 6 patients (27 percent) one month after treatment, all of whom had striae alba . Mild improvement was documented in the remaining 16 patients, all of whom presented with striae rubra. In contrast, striae rubra responded well to fractional laser therapy in a series of 10 patients given up to eight treatments with a 1550 nm fractional laser for new-onset striae distensae on the breast secondary to breast augmentation . Marked improvement in striae rubra was present in all patients four weeks after the final treatment.
Beneficial effects of nonablative fractional laser treatment may persist over time. A retrospective study of 16 women treated with a 1550 nm nonablative fractional laser for abdominal striae rubra or striae alba found similar mean reductions in striae length and width one month and one year after treatment .
Ablative fractional lasers — Ablative fractional laser therapy for striae distensae is usually performed with 10,600 nm fractional CO2 lasers:
●Administration – Fractional ablative laser therapy can be performed in an office setting with local anesthesia; however, some patients require the use of systemic anxiolytics and narcotic pain medication intraoperatively. For safety, treatment density should be much lower on nonfacial sites as compared with facial sites, and it should be applied over four to eight passes to avoid overlap and skip areas.
We routinely use 5 to 15 percent total density coverage when treating patients with skin phototypes I to IV and use a lower density range for higher energy treatments and patients with skin phototypes V or VI (table 2). While treatment with fractional ablative lasers in patients with skin phototypes IV and higher is controversial due to the risk of pigmentary alteration and permanent scarring [69,70], laser experts may be able to safely treat these patients at very low density settings. (See "Ablative laser resurfacing for skin rejuvenation", section on 'Administration'.)
A total of one to three ablative fractional laser treatment sessions usually is sufficient. Because collagen remodeling may occur for several months after each treatment, treatments are usually given at four- to six-month intervals. Compared with nonablative fractional laser therapy, multiple treatment sessions with an ablative fractional laser tend to be less practical because of longer recovery times and greater risk for side effects, particularly for patients with striae involving a large body surface area.
●Recovery and complications – On nonfacial sites, recovery involves approximately one week of serosanguineous discharge and crusting followed by an additional one to two weeks of desquamation and an additional one to two months of erythema. Potential complications of ablative fractional laser therapy include prolonged erythema, infection, postinflammatory hyperpigmentation (particularly in patients with skin phototypes IV to VI (table 2)), and scarring. Local wound care, close clinical follow-up, aggressive sun protection, and antimicrobial and antiviral prophylaxis (where appropriate) can help reduce the risk of complications. (See "Ablative laser resurfacing for skin rejuvenation", section on 'Adverse effects and complications'.)
●Efficacy – Studies evaluating ablative fractional laser therapy for striae distensae are limited and primarily have included patients with striae alba. In a retrospective study of 27 women with striae alba (skin phototype IV) given a single treatment with a fractional CO2 laser system, blinded assessors of clinical photographs noted marked or near-total improvement in striae distensae in 14 patients (59 percent) two months after treatment and lesser improvement in an additional 9 patients . A prospective study evaluating the effects of a novel fractional CO2 device on striae distensae and other disorders found variable results. After three to four treatments, three of five patients had no improvement, one had moderate improvement, and one had advanced improvement . Studies have compared ablative fractional laser therapy with microneedling. (See 'Microneedling devices' below.)
Combination treatment with a pulsed dye laser and an ablative fractional CO2 laser may be more beneficial for striae alba in some patients . A small, uncontrolled study suggests that combination treatment with a 2940 nm erbium:yttrium aluminum garnet (Er:YAG) fractional laser, recombinant bovine basic fibroblast growth factor, and light-emitting diode-red light may also improve striae alba .
Microneedling devices — Microneedling devices deliver a stamped array of thin needles to create microchannels in the dermis, stimulate the wound healing cascade, and induce neocollagenesis . Microneedling induces minimal epidermal injury and has a low risk of pigmentary alterations, even in patients with highly pigmented skin [76,77]. The relative safety of microneedling contributes to its selection as a preferred therapy.
Selection of procedure — Microneedling is often combined with another modality in an attempt to augment efficacy. Most experts, including ourselves, consider treatment with devices that combine microneedling and the delivery of radiofrequency energy (RF microneedling) the preferred mode of microneedling therapy for striae distensae. The combined devices emit radiofrequency energy at the tip of needles or over the needle surface, which is thought to enhance dermal remodeling and clinical effect . Studies that compare the efficacy of RF microneedling and microneedling alone are needed. (See 'Radiofrequency devices' below.)
Alternative modes of microneedling therapy include performance of microneedling alone or in conjunction with platelet-rich plasma (PRP) treatment; however, these interventions are generally considered less effective than RF microneedling. PRP may augment collagen induction through the delivery of growth factors . Like RF microneedling, study data to confirm greater efficacy than microneedling alone are lacking. (See 'Other' below.)
●Administration – A series of RF microneedling sessions are typically performed, with individual treatment sessions separated by four or more weeks, depending upon the time required for healing of skin prior to subsequent treatments. Needle penetration depths usually range from 2 to 3 mm. The approach to microneedling plus PRP and microneedling alone is similar. For microneedling with PRP, PRP is applied to the skin immediately prior to microneedling or injected into the skin.
Noticeable clinical improvement may occur within a few weeks after a treatment session . Treatment is continued until there is a satisfactory response or progressive improvement ceases. A typical treatment course consists of three to six treatments; however, patients may be satisfied with results after fewer treatments .
●Recovery and complications – RF microneedling and other microneedling modalities are generally well tolerated. Adverse effects, such as mild pain, erythema, edema, crusting, bruising, and pinpoint bleeding, typically resolve within one week .
●Efficacy – Data on RF microneedling and microneedling plus PRP for striae distensae are limited. Use of RF microneedling is primarily based upon studies supporting benefit of radiofrequency energy and non-RF microneedling alone for striae distensae, reported benefit in other conditions (eg, acne scars), and expert clinical experience  (see 'Radiofrequency devices' below). Similarly, the addition of PRP is primarily based upon studies that suggest benefit of PRP for striae distensae and benefit of microneedling plus PRP for acne scars [79-83].
There are limited and conflicting data on the relative efficacy of non-RF microneedling compared with ablative fractional laser therapy. There are data that suggest similar efficacy of non-RF microneedling and nonablative fractional laser therapy. Additional study is necessary to clarify relative efficacy:
•A study in which 30 patients with striae alba were treated with a fractional CO2 laser on the right side of the body and microneedling on the left side of the body once per month for a total of three months found a moderate to excellent improvement rate of 55 percent for the microneedling side compared with 76 percent for the ablative fractional laser side . Postinflammatory hyperpigmentation occurred secondary to fractional CO2 laser in 11 patients; microneedling did not result in postinflammatory hyperpigmentation.
In contrast, another study that compared outcomes for fractional CO2 laser and microneedling, both administered once per month for three months, favored microneedling. At least mild improvement occurred in 5 of 10 patients (50 percent) and 9 of 10 patients (90 percent) in the fractional laser and microneedling groups, respectively . There were methodologic differences between the two studies.
•A trial in which 20 women with striae alba underwent random assignment of one-half of the abdomen to either five monthly sessions with microneedling or five monthly sessions with a 1340 nm neodymium:yttrium-aluminum-perovskite nonablative fractional laser found patients' assessment of treatment effect similar for the two groups . An assessment of post-treatment clinical photographs by two independent evaluators one month after the fifth treatment found at least some improvement in 75 to 88 percent of patients in the microneedling group and 75 to 94 percent of patients in the nonablative fractional laser group.
Uncontrolled studies also suggest benefit of microneedling [77,85-87].
Other interventions — Other interventions that may improve striae distensae based upon limited evidence include superficial dermabrasion, phototherapy, chemical peels, intense pulsed light (IPL), radiofrequency devices, infrared lasers, and other therapies. Limited data, unclear benefit, and/or treatment risks preclude recommendations for the routine use of these therapies.
Superficial dermabrasion — Striae rubra may respond to superficial dermabrasion. A randomized, open-label trial with 32 women with narrow, early striae rubra (≤6 months old) compared the efficacy of 16 weekly sessions of superficial dermabrasion to daily application of topical tretinoin 0.05% cream for 16 weeks . Both treatments demonstrated significant improvement of early striae rubra from baseline, and there was no significant difference in efficacy. Superficial dermabrasion had a lower incidence of side effects. Common side effects of superficial dermabrasion include scaling, pruritus, and erythema.
Phototherapy — Phototherapy may improve hypopigmentation in striae alba. A beneficial effect of this treatment is supported by a prospective, uncontrolled study in which treatment of striae alba with up to 15 sessions with an ultraviolet B (UVB) range excimer laser was associated with 76 percent or greater darkening within striae in all patients after an average of eight treatments . In addition, a study in which striae alba that were treated with an excimer laser in nine patients were compared with untreated striae alba in the same patients found a mean percentage pigment correction of 68 percent in treated areas relative to untreated areas . Not all studies have yielded such favorable results. An uncontrolled study of 10 patients with striae alba given up to 10 treatment sessions with an excimer laser found greater than 50 percent repigmentation in only two patients . Study protocol differences may have contributed to the variation in results.
When beneficial, the effects of excimer laser therapy appear to diminish over time , suggesting that maintenance therapy may be necessary to maintain the response to treatment. Excimer laser therapy does not improve the atrophy and abnormal skin texture of striae distensae.
Other forms of phototherapy may be useful. In a small, uncontrolled study, targeted narrowband UVB/ultraviolet A1 (UVA1) therapy improved hypopigmentation in striae alba .
Potential side effects of phototherapy include erythema, burning, and hyperpigmentation of adjacent skin. Adverse effects of UVB phototherapy are reviewed in greater detail separately. (See "UVB therapy (broadband and narrowband)", section on 'Short- and long-term adverse effects'.)
Chemical peels — Superficial chemical peels may improve striae distensae by increasing collagen synthesis [92-94]. A prospective, nonrandomized study (n = 40) that compared the effect of six once-monthly 70% glycolic acid chemical peels on striae distensae on the left thigh with placebo on the right thigh showed a significant decrease in furrow width and hemoglobin levels by spectrophotometry in those with striae rubra . Participants with striae alba also demonstrated a similar decrease in furrow width as well as an increase in melanin levels by spectrophotometry. No significant differences in these parameters were demonstrated in the placebo-treated areas.
Potential side effects of superficial chemical peels include, erythema, scaling, and postinflammatory hyperpigmentation. Caution should be taken when applying high concentrations of glycolic acid or other chemical peels, especially in patients with skin phototypes IV to VI (table 2) because of the risk for postinflammatory pigmentary alteration.
Intense pulsed light — Intense pulsed light (IPL) may be an alternative to pulsed dye laser therapy for striae rubra. A comparative study in which 20 patients with striae rubra (16 patients) or striae alba (4 patients) received five sessions of pulsed dye laser therapy on one side of the body and IPL therapy on the contralateral side found clinical improvement in striae width and skin texture with both treatments . In comparison with striae alba, striae rubra demonstrated better clinical responses to both therapies. Histologic evaluation of striae revealed increases in collagen after both therapies. However, a statistically significant increase in collagen I expression was detected with pulsed dye laser therapy but not IPL therapy. (See "Nonablative skin resurfacing for skin rejuvenation", section on 'Intense pulsed light'.)
Although the response of striae alba to IPL was less than the response of striae rubra in the comparative study, striae alba seem to respond to IPL treatment . An uncontrolled study of 15 women with striae alba also found benefit . After five IPL treatments, all of the women demonstrated clinical and microscopic improvement.
Potential side effects of IPL include erythema, blistering, dyspigmentation, and scarring.
Radiofrequency devices — Noninvasive radiofrequency devices have been used alone or in combination with other modalities to induce dermal remodeling and subtle tightening of the skin, leading to improvement in striae distensae [78,97-102]. As monotherapy, clinical efficacy is modest overall and the durability of effect is unclear. (See "Nonablative skin resurfacing for skin rejuvenation", section on 'Radiofrequency'.)
Radiofrequency devices have been combined with other therapies in attempts to augment the response to treatment. In small, uncontrolled studies, combined use of radiofrequency devices with pulsed dye laser treatment  or autologous PRP [101,102] has been reported to be of benefit. In a prospective study of 30 patients with striae distensae, combination therapy with a fractionated microneedle radiofrequency device and fractional CO2 laser demonstrated a trend towards greater improvement compared with improvement from either treatment as monotherapy . Radiofrequency energy combined with a pulsed magnetic field appeared to improve striae distensae in an uncontrolled study with 16 patients .
Radiofrequency devices do not induce epidermal injury, and treatment is generally well tolerated.
Infrared lasers — The 1064 nm neodymium-doped yttrium aluminium garnet (Nd:YAG) laser can be used to target vascular structures and may also induce modest dermal collagen remodeling [103,104], features that may be useful for the treatment of striae rubra. An uncontrolled study in which 20 adults with striae rubra were given an average of 3.45 treatments with a 1064 nm long-pulsed Nd:YAG laser found excellent (>70 percent) improvement in the appearance of striae rubra in eight patients and good (30 to 70 percent) improvement in an additional eight patients . Treatment was well tolerated, complicated only by mild, transient erythema and edema. (See "Nonablative skin resurfacing for skin rejuvenation", section on 'Infrared lasers and light devices'.)
Treatment with other nonablative infrared lasers has been attempted, such as the 1320 nm Nd:YAG and 1450 nm diode lasers. However, these devices yielded poor clinical outcomes and an unacceptably high incidence of postinflammatory pigmentation .
Other — Limited data suggest that regimens incorporating 20% glycolic acid , topical silicone or nonsilicone gels applied with massage , sand abrasion and trichloroacetic acid , succinylated atelocollagen , or a product containing onion extract and Centella asiatica  may be beneficial for the treatment of striae distensae. Further study is necessary to clarify the role of these treatments. Our clinical experience suggests that the 532 nm potassium titanyl phosphate (KTP) laser may also be of benefit for the treatment of striae rubra.
PREVENTION — Interventions for the prevention of striae distensae are usually discussed in the context of pregnancy given the common and expected occurrence of striae distensae in pregnant women. Although many women use a wide variety of creams, lotions, and ointments in attempts to reduce risk for striae development, strong evidence to confirm efficacy of any of these interventions is lacking [109,110].
A 2012 systematic review of randomized trials that included trials assessing olive oil; cocoa butter; a product containing hyaluronic acid, vitamins A and E, allantoin, and calcium pantothenate; a product containing C. asiatica extract, alpha-tocopherol, and collagen-elastin hydrolysates; and a product containing vitamin E, essential free fatty acids, panthenol, hyaluronic acid, elastin, and menthol found no high-quality evidence to support the use of these topical preparations to prevent striae distensae during pregnancy . In addition, a subsequent randomized trial (n = 360) comparing use of olive oil or a cream containing lanolin, stearin, triethanolamine, almond oil, and other ingredients with no treatment found that neither intervention was effective for prevention .
Many "belly band" garments to support the abdomen are marketed to pregnant women. However, efficacy of peripartum or postpartum use for preventing or treating striae distensae is unproven.
Topical retinoids may be beneficial for the treatment of early striae distensae but, due to fetal safety concerns, should not be used for prevention or treatment during pregnancy. (See 'Topical retinoids' above.)
SUMMARY AND RECOMMENDATIONS
●Striae distensae (stretch marks) are a common form of dermal scarring that usually appear as linear erythematous, violaceous, or hypopigmented striations. Predisposing factors include pregnancy, adolescence, drug exposure (eg, topical or systemic corticosteroids), underlying disease (eg, Cushing's syndrome or Marfan syndrome), and surgery (eg, breast augmentation). (See 'Epidemiology and risk factors' above.)
●The pathogenesis of striae distensae is not well understood. Mechanical forces on the skin, intrinsic alterations in skin structure or function, and hormonal factors may play a role. (See 'Pathogenesis' above.)
●The two main clinical presentations of striae distensae are striae rubra and striae alba. Striae rubra precede striae alba and are characterized by an erythematous to violaceous color (picture 1A-C). Striae rubra eventually evolve into the hypopigmented, scar-like, and atrophic plaques known as striae alba (picture 2A-B). Common sites for striae distensae are the abdomen, breasts, medial upper arms, hips, lower back, buttocks, and thighs. (See 'Clinical manifestations' above.)
●The diagnosis of striae distensae can usually be made easily during the physical examination. A biopsy usually is not necessary. The major disorder in the differential diagnosis is linear focal elastosis. (See 'Diagnosis' above and 'Differential diagnosis' above.)
●For patients with striae rubra who desire treatment, we suggest pulsed dye laser therapy as initial treatment rather than other treatments (Grade 2C). For patients who prefer to avoid laser therapy, topical tretinoin is a reasonable alternative. Disadvantages of tretinoin include the need to adhere to at least several months of daily therapy and the potential for skin irritation. (See 'Pulsed dye lasers' above and 'Topical retinoids' above.)
●For patients with striae alba, we suggest fractional laser therapy or microneedling as initial treatment (Grade 2B). Microneedling is preferred over fractional laser therapy for patients with skin phototypes IV to VI because of increased risk for laser-induced hyperpigmentation in this population.
We use microneedling with radiofrequency (RF microneedling), rather than other modalities of microneedling, when RF microneedling is available. Nonablative fractional lasers are often preferred over ablative fractional lasers due to lower risk of complications and shorter recovery times.