Version May 2024
INTRODUCTION — The initial approach to the patient presenting with a skin problem requires a detailed history of the current skin complaint and a complete skin examination (figure 1A-B) [1]. In many cases, the patient's general medical history may be relevant to the diagnosis of skin disorders. Although the history and visual aspects are of primary importance in the recognition of skin diseases, sometimes additional tests (eg, laboratory tests, skin biopsy) are required for accurate diagnosis. (See "Office-based dermatologic diagnostic procedures" and "Skin biopsy techniques".)
This topic will discuss the general approach to dermatologic diagnosis. The approach to the patient with specific skin signs and symptoms is discussed separately. Skin biopsy techniques are discussed separately. Laboratory tests used to refine or confirm a dermatologic diagnosis are discussed in relevant topics. The approach to the patient with hair or nail abnormalities or oral lesions is also discussed separately.
●(See "Approach to the patient with cutaneous blisters".)
●(See "Pruritus: Etiology and patient evaluation".)
●(See "Acquired hyperpigmentation disorders".)
●(See "Congenital and inherited hyperpigmentation disorders".)
●(See "Acquired hypopigmentation disorders other than vitiligo".)
●(See "Approach to the patient with facial erythema".)
●(See "Approach to the patient with pustular skin lesions".)
●(See "Skin biopsy techniques".)
●(See "Evaluation and diagnosis of hair loss".)
●(See "Approach to the patient with a scalp disorder".)
●(See "Overview of nail disorders".)
●(See "Oral lesions".)
●(See "Approach to the patient with retiform (angulated) purpura".)
●(See "Approach to the patient with annular skin lesions".)
●(See "Approach to the patient with an intertriginous skin disorder".)
●(See "Approach to the differential diagnosis of leg ulcers".)
HISTORY — The most important initial questions to ask patients with a skin problem include the following:
●How long has the eruption or lesion been present?
●How did it look when it first appeared, and how is it now different?
●Where did it first appear, and where is it now?
●What associated symptoms, such as itching, stinging, tenderness, or pain, are associated with the lesion?
●Are any other family members affected or have a similar history?
●Has the patient ever had this rash or lesion before? If so, what treatment was used, and what was the response?
●What does the patient think caused the rash or lesions?
●What does the patient think exacerbates or alleviates the rash or lesions?
●What is the patient's usual skin care regimen?
●Is anything new or different (eg, medications, personal care products, occupational or recreational exposures)?
●How does the skin problem impact the patient's life?
●What treatments have been used, and what was the response, this time and previously?
Additional questions that may be helpful include:
●Does the patient have any acute or chronic medical conditions?
●What medications does the patient take currently, what have they recently taken, including over-the-counter and herbal therapies?
●Is there a family history of skin disorders or skin cancer?
●Has there been any increase in stress in their life?
●What is the social history, including occupation, hobbies, travel?
●Does the patient have any allergies?
●Does the patient have pets?
●Does the patient have risk factors for sexually transmitted diseases?
PHYSICAL EXAMINATION — The physical examination of a patient with a skin complaint, which includes visual inspection and palpation of the skin and sometimes additional examination aided by a Wood's lamp or a dermatoscope, is aimed at assessing the following:
●Morphology of individual lesions (type of lesion)
●Distribution of lesions
●Color
●Consistency and feel
●Number of lesions present
●Arrangement of multiple lesions (eg, scattered, clustered, grouped, linear, zosteriform, or coalescing)
Visual inspection — The patient should always be examined in a good light and with a magnifying lens, if necessary. Ideally, the entire skin should be examined in every patient, particularly if the diagnosis is in doubt, as this may reveal lesions that are more representative and have not been modified by secondary changes [1]. Moreover, a full-body skin examination, including nails, hair, and mucosal surfaces, may reveal a lesion or eruption of which the patient may be unaware.
Patients may occasionally provide self-taken digital images of skin lesions or eruptions. They may be useful in assessing changes over time or documenting evanescent eruptions, such as urticaria.
For the experienced clinician, visual inspection may sometimes provide an instant diagnosis. However, such apparently effortless pattern recognition is actually an extremely complex "nonanalytical reasoning" process where the individual components are analyzed separately [1-3].
Knowing which conditions are more frequently diagnosed can assist the clinician in arriving at the most likely diagnosis for a given patient. In the United States, the top 10 most common dermatologic conditions seen by dermatologists and nondermatologists between 2001 and 2010 were acne, actinic keratosis, nonmelanoma skin cancer, benign tumors, contact dermatitis, seborrheic keratosis, viral warts, psoriasis, rosacea, and epidermoid cyst [4].
Examination of darkly pigmented skin — The examination of patients with moderately to darkly pigmented skin (Fitzpatrick skin types IV to VI (table 1)) requires a degree of clinical experience because the amount of pigmentation clearly influences the characteristics of certain skin lesions. In patients with darkly pigmented skin, most dermatoses induce darkening or lightening of the skin that affect our perception of the color of the lesion and overwhelm other clinical manifestations [5]:
●Erythema may be particularly challenging to detect in individuals with darkly pigmented skin, as it may appear dark brown or violaceous instead of pink or red, as typically seen in patients with lightly pigmented skin. As an example, rosacea may be underdiagnosed in patients with darker skin tones because erythema and telangiectasias are more difficult to appreciate in darker skin (picture 1) [6].
●The typical erythematous and scaly lesions of eczema may appear as scaly lesions with a grayish, violaceous, or dark brown hue (picture 2A-B). Hyperpigmented areas may be mistaken for postinflammatory hyperpigmentation, when in fact they are a marker of active inflammation.
●Wheals of urticaria appear skin-colored or paler because dermal edema lightens the skin (picture 3A-B). Papules may be pale or dark according to the degree of edema or the presence of acanthosis or hyperkeratosis, which mask the natural pigmentation.
●Purpura may be difficult to detect, as it may be obscured by the skin color (picture 4A).
●Dry skin may have a whitish or ashy color and a reduction in skin shininess (picture 5).
●Postinflammatory hypopigmentation (picture 6) and hyperpigmentation (picture 7A) are exaggerated in darkly pigmented skin compared with lighter skin.
Palpation of the skin — In addition to visual examination, palpation of skin lesions has a central role in the diagnosis of skin diseases [7]. Intact skin can be palpated without gloves after hands are sanitized or washed. Gloves should be worn when palpating nonintact skin and for the examination of the mouth, genital, and perineal region.
Palpation provides information on the quality of scale or keratosis, texture changes, and skin temperature, and detects consistency, induration, tenderness, depth, and fixation of a lesion. Exerting pressure on the skin can demonstrate edema, blanching, or dermal defects. Examples of the usefulness of skin palpation include:
●In morphea or scleroderma, dermal fibrosis can be felt as skin induration on palpation, where visual inspection would detect only nonspecific hypo- or hyperpigmentation. (See "Pathogenesis, clinical manifestations, and diagnosis of morphea (localized scleroderma) in adults".)
●Thin actinic keratoses are more easily "felt" than seen. (See "Actinic keratosis: Epidemiology, clinical features, and diagnosis".)
●In a patient presenting with bullae, applying shearing forces to the skin can show skin detachment, as in the Nikolsky sign in pemphigus. (See "Approach to the patient with cutaneous blisters", section on 'Nikolsky sign'.)
●Stroking or rubbing with a tongue blade can demonstrate dermographism or urtication of mast cell lesions (Darier's sign). (See "Physical (inducible) forms of urticaria", section on 'Dermographism' and "Mastocytosis (cutaneous and systemic) in adults: Epidemiology, pathogenesis, clinical manifestations, and diagnosis", section on 'Darier's sign'.)
●Olfactory clues may help establish a diagnosis in rare cases. For instance, the epidermolytic ichthyoses have a distinctive odor, as does pseudomonas infection.
ADDITIONAL EXAMINATION
Wood's light examination — A Wood's light is a hand-held source of ultraviolet light from which virtually all visible rays have been excluded by a Wood's (nickel oxide) filter. Under Wood's light, variations in epidermal pigmentation are more apparent than under visible light, and some microorganisms may emit a fluorescence. As an example, the depigmented areas of vitiligo are greatly enhanced under Wood's light, and erythrasma patches may appear as pink fluorescent areas. (See "Office-based dermatologic diagnostic procedures", section on 'Wood's lamp examination (black light)'.)
Dermoscopic examination — Dermoscopy, also known as dermatoscopy or epiluminescence microscopy, is a skin examination technique performed with a handheld instrument called a dermatoscope. The procedure allows for the visualization of subsurface skin structures in the epidermis, dermoepidermal junction, and upper dermis that are usually not visible to the naked eye (picture 8A-B).
Dermoscopy is primarily used for the examination of pigmented skin lesions but can also assist clinicians in assessing many nonpigmented skin lesions [8-10]. In general dermatology and in primary care practices, the primary purpose of dermoscopy is the evaluation of pigmented and nonpigmented skin lesions to decide whether or not a lesion should be biopsied or referred [11,12].
Dermoscopy requires some formal training to be effectively practiced [13,14]. Online tutorials on dermoscopy can be found at www.dermnetnz.org, www.dermoscopy-ids.org, or https://dermoscopedia.org.
The principles of dermoscopy and dermoscopic examination of cutaneous lesions are discussed in detail separately. (See "Overview of dermoscopy" and "Dermoscopic evaluation of skin lesions" and "Dermoscopy of facial lesions" and "Dermoscopy of mucosal lesions" and "Dermoscopy of pigmented lesions of the palms and soles" and "Overview of dermoscopy of the hair and scalp" and "Dermoscopy of nail pigmentations" and "Dermoscopy of nonpigmented nail lesions".)
LESION MORPHOLOGY AND DISTRIBUTION — Two of the most useful characteristics that aid in forming a differential diagnosis are the morphology of individual lesions (type of lesion) and distribution of lesions. The arrangement of lesions in relationship to each other, the color of lesions, and the consistency and feel of lesions also add important information.
Primary lesions — Primary lesions represent the initial pathologic change. The terms used to describe primary skin lesions include the following:
●Macules – Macules are nonpalpable lesions <1 cm that vary in pigmentation from the surrounding skin (picture 9A-C). Patches are nonpalpable lesions >1 cm. These lesions are flush with the surrounding skin. The differential diagnosis of macules is shown in the table (table 2).
●Papules – Papules are palpable, discrete lesions measuring <1 cm in diameter (picture 10). They may be isolated or grouped. The differential diagnosis of papules is shown in the table (table 3).
●Plaques – Plaques are elevated lesions that are >1 cm in diameter. Plaques may be formed by a confluence of papules (picture 11A-B). The differential diagnosis of plaques is shown in the table (table 4).
●Nodules – Nodules are palpable, solid or cystic, discrete lesions measuring between 1 and 2 cm in diameter. Tumors are solid or cystic, discrete lesions measuring >2 cm in diameter. These lesions may be isolated or grouped and may or may not have surface changes (picture 12A-B). The differential diagnosis of tumors and nodules is shown in the table (table 5). (See "Overview of benign lesions of the skin".)
●Telangiectasia – Telangiectasia is a dilated, superficial blood vessel (picture 13).
●Purpura – Purpura are red-purple lesions that do not blanch under pressure, resulting from the extravasation of blood from cutaneous vessels into the skin. Purpuric lesions can be macular or raised (palpable purpura) (picture 4A-D). Petechiae are pinpoint, purpuric lesions 1 to 2 mm in diameter (picture 14A-B). Ecchymoses (bruises) are larger extravasations of blood (picture 15).
●Pustules – Pustules are small, circumscribed skin papules containing purulent material (picture 16A-B). The differential diagnosis of pustules is shown in the table (table 6).
●Vesicles – Vesicles are small (<1 cm in diameter), circumscribed skin papules containing clear serous or hemorrhagic fluid (picture 17). Bullae are large (>1 cm in diameter) vesicles. The differential diagnosis of vesicles and bullae is shown in the table (table 7).
●Wheals – Wheals are irregularly shaped, elevated, edematous skin areas that may be erythematous or paler than surrounding skin (picture 3A-C). The borders of a wheal are well demarcated but not stable; they may move to adjacent, uninvolved areas over periods of hours.
●Scale – Scale is flakes on the skin surface formed by desiccated, thin plates of cornified epidermal cells (picture 18A-B).
●Atrophy – Atrophy is a depression from the surface of the skin caused by underlying loss of epidermal or dermal substance (picture 19A-B).
●Hyperpigmentation – Hyperpigmentation is increased skin pigment (picture 7A-B); hypopigmentation is decreased skin pigment (picture 20). Depigmentation is total loss of skin pigment (picture 21).
Secondary lesions — Secondary lesions of the skin represent evolved changes from the skin disorder, due to secondary external forces, such as scratching, picking, infection, or healing. Examples include:
●Excoriation – Excoriation describes superficial, often linear skin erosion caused by scratching (picture 22A-B).
●Lichenification – Lichenification is dry, leathery thickening of the skin with exaggerated skin markings secondary to chronic inflammation caused by scratching or other irritation (picture 2B-E).
●Edema – Edema is swelling due to accumulation of water in tissue (picture 23).
●Scale – Scale describes superficial epidermal cells that are dead and cast off from the skin (picture 24).
●Crust – Crust is dried exudate of serum, blood, sebum, or purulent material on the surface of the skin, a "scab" (picture 25).
●Fissure – Fissure is a deep skin split extending into the dermis (picture 26).
●Erosion – Erosion is a superficial, focal loss of part of the epidermis (picture 27A-B). Ulceration is focal loss of the epidermis extending into the dermis. Lesions may heal with scarring (picture 28). The differential diagnosis of erosions and ulcers is shown in the table (table 8).
●Scar – Scar is fibrous tissue that replaces normal dermal or subcutaneous tissue after skin injury (picture 29).
Lesion distribution — The location of one or multiple skin lesions and the arrangement of multiple lesions in relation to each other can suggest a particular diagnosis. Initial differential diagnoses based on typical distributions of common skin dermatoses are summarized in the table (table 9) and shown graphically in the figures (figure 1A-B).
Common arrangements of lesions are:
●Clustered, as seen in herpes simplex infections (picture 17)
●Grouped, as seen in dermatitis herpetiformis (picture 30A-B) and granuloma annulare (picture 31)
●Linear, as seen in contact dermatitis (picture 32 and picture 33) and morphea (picture 34A-B)
●Zosteriform, as seen in herpes zoster infection (picture 35A-C) and metastatic breast carcinoma
●Coalescing or confluent, as seen in psoriasis and viral exanthems (picture 36)
SUMMARY
●Initial approach – The initial approach to the patient presenting with a skin problem requires a detailed history of the current skin complaint, medical and medication history, and a full body skin examination, including the scalp, nails, and mucosal surfaces.
●History of the skin lesion/eruption – Key questions for the patient include the time of onset, duration, location, evolution, and symptoms of the rash or lesion. Additional information on family history, occupational exposures, comorbidities, medications, and social or psychologic factors may be helpful. (See 'History' above.)
●Physical examination – The patient should always be examined in a good light and with a magnifying lens, if necessary. The physical examination includes visual inspection and palpation of the skin. The morphology, arrangement, and distribution of the lesions are cardinal features to be identified by visual inspection and palpation. (See 'Visual inspection' above and 'Palpation of the skin' above.)
●Examination of darkly pigmented skin – The examination of patients with moderately to darkly pigmented skin requires a degree of clinical experience because the amount of pigmentation influences the characteristics of certain skin lesions. As an example, in individuals with darkly pigmented skin, the typical erythematous and scaly lesions of eczema may appear dark brown, black, or violaceous (picture 2A-B). (See 'Examination of darkly pigmented skin' above.)
●Additional examination – Sometimes, the clinical examination requires additional examination, aided by a Wood's lamp or a dermatoscope:
•Wood's light examination – Under Wood's light, variations in epidermal pigmentation are more apparent than under visible light, and some microorganisms may emit a fluorescence. (See "Office-based dermatologic diagnostic procedures", section on 'Wood's lamp examination (black light)'.)
•Dermoscopic examination – Dermoscopy is a skin examination technique performed with a handheld instrument called a dermatoscope, which allows for the visualization of subsurface skin structures in the epidermis, dermoepidermal junction, and upper dermis not visible to the naked eye (picture 8A-B). (See "Dermoscopic evaluation of skin lesions".)
●Lesion morphology and distribution – The morphology, arrangement, and distribution of the lesions are cardinal features to be identified by visual inspection and palpation. In many cases, the location of one or multiple skin lesions and the arrangement of multiple lesions in relation to each other can suggest a particular diagnosis (table 9 and figure 1A-B). (See 'Lesion morphology and distribution' above.)
ACKNOWLEDGMENT — The editorial staff at UpToDate acknowledge Adam O Goldstein, MD, MPH, and Beth G Goldstein, MD, who contributed to an earlier version of this topic review.
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