Version July 2025
INTRODUCTION —
Lymphedema is defined as the abnormal accumulation of interstitial fluid and fibroadipose tissues resulting from reduced lymph transport because of injury, infection, cancer and its treatment, or congenital abnormalities of the lymphatic system. Lymphedema is classified as primary or secondary depending on etiology and presentation. While lymphedema most commonly affects the extremities, it can also occur in other areas of the body (eg, chest, abdomen, genital region, face, neck).
The pathophysiology, classification, and causes of lymphedema affecting predominantly the extremities (ie, peripheral lymphedema) are reviewed. The clinical features, diagnosis, and management of lymphedema are reviewed separately.
●(See "Clinical features, diagnosis, and staging of peripheral lymphedema".)
●(See "Management of peripheral lymphedema".)
NORMAL LYMPHATIC SYSTEM
Lymphatic flow — Lymph flow takes place in a low-pressure system. Uptake of interstitial fluid begins in lymphatic capillaries and precollectors that abut the interstitial space. The process is facilitated by skeletal muscle contraction in the extremity. The initial lymphatics merge into vessels of increasing caliber that are partially surrounded by a specialized smooth muscle layer that, upon contraction, promotes peristaltic movement of the lymph fluid toward the systemic circulation. In addition, lymphatic collectors have unidirectional valves that prevent retrograde flow.
In the extremities, the superficial lymphatic system drains interstitial fluid from the skin and subcutaneous tissue into larger collecting vessels (ie, deep lymphatics) [1-3]. The deep lymphatics drain into the regional lymph nodes (figure 1) where foreign material is filtered and where antigen-presenting cells interact with T and B cells to activate immune responses [1,2]. (See 'Upper extremity lymph nodes' below and 'Lower extremity lymph nodes' below.)
●The lymph draining from both lower extremities, the gastrointestinal tract, and the left upper body (left upper extremity, left chest wall, left upper back, left shoulder, and left breast) enter the venous circulation through the thoracic duct, which opens into the venous angle between the left subclavian vein and left internal jugular vein (figure 2).
●The lymph draining from the right upper extremity, right chest wall, right upper back, right shoulder, and right breast drains into the right lymphatic duct via a similar right-sided venous angle between the right subclavian vein and right internal jugular vein.
Upper extremity lymph nodes — The lymph nodes of the upper extremity, breast, and chest wall include:
●Epitrochlear nodes – The epitrochlear lymph nodes lie 1 to 2 cm proximal to the medial epicondyle posterior to the basilic vein and medial to the brachialis muscle.
●Axillary nodes – The deep lymphatics of the upper extremity drain into the axillary lymph nodes. The axillary nodes are divided into three levels based on their relationship to the pectoralis minor muscle.
•Level I nodes – Level I nodes are inferior and lateral to the pectoralis minor muscle
•Level II nodes – Level II nodes are posterior to the pectoralis minor muscle and inferior to the axillary vein
•Level III nodes – Level III nodes are medial to the pectoralis minor muscle
Superficial lymph-collecting vessels in the anterior upper torso drain radially after passing over or through breast tissue. The lymphatics of the breast drain into the axillary and supraclavicular nodes laterally and superiorly (figure 3). Separate perforating lymph-collecting vessels drain to the ipsilateral internal mammary nodes.
Lower extremity lymph nodes — The lymph nodes of the lower extremities consist of the popliteal and inguinal nodes (figure 4). The superficial lymphatic system drains the skin and subcutaneous tissue, paralleling the pattern of venous drainage. The superficial lymphatic vessels then drain into the deep lymphatic system and into the lymph nodes of the pelvis.
●Popliteal nodes – The popliteal nodes are small, deep lymph nodes located posterior to the knee, close to the popliteal vessels. They drain lymph from superficial vessels and deep areas of the leg and foot. The popliteal nodes drain into the deep and superficial inguinal nodes [4].
●Inguinal nodes – The lymphatics of the inguinal region are composed of a network of lymph nodes and vessels, connecting the lower extremities to the pelvic region and abdomen (figure 5). The inguinal lymph nodes are located in the femoral triangle and are grouped into superficial and deep (subinguinal) lymph nodes, relative to the deep fascia [3,5,6].
•Superficial inguinal nodes – The superficial inguinal lymph nodes arise from the superior part of the femoral canal immediately below the inguinal ligament. These facilitate drainage of the penis, scrotum, labia, perineum, buttock, and lower abdominal wall.
•Subinguinal nodes – The subinguinal nodes are classified as either superficial or deep.
-The superficial subinguinal nodes can be identified on both sides of the superior aspect of the great saphenous vein. These lymph nodes mainly receive afferents from the superficial lymphatic vessels of the lower extremity and also provide adjunctive drainage to the penis, scrotum, labia, perineum, and buttock.
-The deep subinguinal nodes are situated below the deep fascia, along the medial to the femoral vein. These nodes receive afferent drainage from the deep lymphatic trunks, including the femoral vessels, the lymphatics from the glans penis or clitoris, and superficial subinguinal glands.
PATHOPHYSIOLOGY —
Lymphedema is a low-output failure of the lymphatic system (ie, lymph transport is reduced). It is important to note that the rate of capillary filtration is normal in patients with lymphedema, in contrast to those with generalized edematous states, for which intact lymphatics are overwhelmed by an excessive amount of capillary infiltrate (ie, high-output failure of the lymphatics) [7]. In some cases where high-output failure of the lymphatic system is chronic (eg, recurrent infection, thermal burns, chronic venous insufficiency), a mixed form of edema/lymphedema can develop. (See "Pathophysiology and etiology of edema in adults".)
The persistent accumulation of lymphatic fluid activates and maintains a chronic inflammatory state that promotes the proliferation of adipocytes and the deposition of collagen fibers in the extracellular matrix and around capillary and collecting lymphatics, with resultant tissue fibrosis [8,9].
Mechanisms of reduced lymph transport — Lymphedema develops when the lymphatic load exceeds the transport capacity of the lymphatic system, which causes filtered fluid to accumulate in the interstitium leading to swelling [7,10]. This imbalance between interstitial fluid production and transport may be due to a variety of mechanisms:
●Congenital malformation of the lymphatic system
●Damage to the lymphatic vessels leading to a reduction in the number of lymph channels (eg, radiation therapy, medication effects)
●Damage or removal of lymph nodes leading to a reduction in the number of lymph nodes (eg, lymphadenectomy, trauma)
●Obstruction of the available lymphatic channels or nodes (eg, compression by a tumor)
●Infiltration of lymphatic vessels (eg, lymphangitic carcinomatosis)
Consequences of lymphedema — Because of the reduced lymph flow and reduced immune function, the skin is at risk for recurrent infections, including cellulitis, erysipelas, and lymphangitis. Chronic lymphedema can also result in a rare form of sarcoma. Lymphedema also has a negative impact on quality of life and can result in significant psychological comorbidity. (See "Clinical features, diagnosis, and staging of peripheral lymphedema".)
ETIOLOGIC CLASSIFICATION —
Lymphedema can be categorized as either primary or secondary [10,11]. The direct cause of primary lymphedema is unknown and may develop at any point in life. Secondary lymphedema develops because of the natural history or treatment of another condition.
Primary — Lymphedema without an inciting factor is termed primary lymphedema. It is generally due to a congenital or inherited condition associated with the pathologic development of the lymphatic vessels. Primary lymphedema more frequently involves the lower extremities compared with the upper extremities.
The differences between primary and secondary lymphedema are not absolute. Although some findings may be more common in one or another, patients with primary or secondary lymphedema can present with the entire spectrum of physical findings. (See "Clinical features, diagnosis, and staging of peripheral lymphedema".)
Primary lymphedema is categorized according to the age at which lymphedema symptoms first present. Primary lymphedema often presents in childhood, but later presentations in adulthood also occur.
Congenital lymphedema — Congenital lymphedema is defined as lymphedema that is present at birth or within the first year of life. It may be either sporadic or familial. It is estimated that congenital lymphedema accounts for about 10 to 25 percent of primary lymphedema cases, affecting females twice as often as males [7].
Lymphedema praecox — Lymphedema praecox is the most prevalent type of primary lymphedema, presenting between ages 1 and 35, most often during puberty. Like congenital lymphedema, lymphedema praecox is more frequent in females than males (ratio of 4:1). Seventy percent of patients with lymphedema praecox present with unilateral lower extremity lymphedema [12].
Lymphedema tarda — Lymphedema tarda is the least common type of primary lymphedema, accounting for <10 percent of cases. Lymphedema tarda manifests clinically after age 35, typically affecting the lower extremities. As with other types of primary lymphedema, lymphedema tarda is more common in females than males [11].
Secondary — Lymphedema that occurs as the result of other conditions or treatments is termed secondary lymphedema. Secondary lymphedema is much more common than primary lymphedema and is often associated with cancer and cancer treatment, infection, inflammatory disorders, obesity, and chronic forms of lymphatic overload (eg, chronic venous insufficiency, trauma/burns). These are discussed in detail below.
CAUSES OF LYMPHEDEMA —
Estimates of the prevalence of lymphedema vary widely depending on the population studied [13-19].
●Upper extremity – The majority of cases of upper extremity lymphedema are secondary and due to malignancy or its treatment [14,17,20,21]. However, other etiologies contribute as well, including the sequelae of trauma, infectious disease, and primary causes [20].
●Lower extremity – Primary causes of lymphedema are more common in the lower compared with the upper extremity [22]. Nevertheless, secondary causes of lymphedema predominate [23]. Cancer and cancer treatment-related lymphedema are common [19,24], but obesity-related lymphedema and lymphedema associated with chronic venous insufficiency (CVI) are frequent secondary causes of lymphedema in the lower extremity [25,26].
Cancer and cancer treatment — The incidence of cancer-related lymphedema varies by type of malignancy and treatment. Cancer-related lower extremity lymphedema has been reported as a complication following the treatment of breast cancer, extremity melanoma, gynecologic malignancy, genitourinary malignancy, and others. (See 'Specific cancers' below.)
Lymphedema is a significant survivorship issue after the surgical treatment of breast cancer with an incidence that varies widely depending on the population studied, type of cancer treatment, and duration of follow-up. (See 'Breast cancer' below.)
Apart from breast cancer, secondary lymphedema is also a consequence of the treatment of other tumors [19,20,23,24]. In a systematic review that included 43 studies of nonbreast cancer, the overall incidence of lymphedema for nonbreast malignancies was 16 percent [23]. The reported incidences of lymphedema for specific malignancies were as follows:
●Lower extremity melanoma – 28 percent
●Gynecologic cancer – 20 percent
●Genitourinary cancer – 10 percent
●Sarcoma – 30 percent
Cancer-associated lymphedema can occur in several ways [27]:
●Obstruction of lymphatic channels or nodes – Tumor compression of lymphatic channels or nodes can result in the development of lymphedema.
●Infiltration of lymphatic vessels – Tumor cells can infiltrate the lymphatic channels (also called lymphangitic carcinomatosis).
●Lymphatic dissection/lymphadenectomy – Disruption or removal of lymph nodes at the time of surgery can increase the risk of lymphedema in patients with cancer.
●Regional lymph node irradiation – Radiation can destroy lymphatic channels, decreasing lymphatic transport. However, radiation therapy alone is rarely enough to result in the development of lymphedema.
●Medication effects
Lymphadenectomy — Lymphadenectomy is perhaps the strongest predictor of lymphedema, and it is associated with an increased risk of lymphedema regardless of the cancer type. It is the primary cause of lymphedema in patients with breast cancer, prostate cancer, endometrial cancer, cervical cancer, and melanoma [2,24,28]. Fortunately, contemporary treatment does not mandate node dissection in those who are clinically node negative. Limiting the extent of lymph node removal is the only measure shown to reduce the incidence of cancer-associated lymphedema. Nodal staging with sentinel lymph node biopsy has reduced the number of lymph node dissections performed and, consequently, the incidence of lymphedema [29]. (See 'Specific cancers' below.)
Beyond lymphadenectomy, the likelihood of developing lymphedema following surgery is related to other factors such as [23]:
●Increasing body mass index (BMI) (see 'Obesity' below)
●Extent of the primary surgery
●Tumor location
●Delayed wound healing
●Postoperative infection
●Postoperative hematoma or seroma
Radiation therapy — The increased risk for lymphedema in patients treated with radiation therapy is best illustrated in patients with breast cancer. Radiation therapy is an additive risk factor for those who have undergone axillary node dissection [30-32]. In a systematic review, the incidence of lymphedema was significantly increased among those who underwent surgery plus axillary radiation therapy compared with surgery alone (41 versus 17 percent) [30]. In another report, the incidence of subjective lymphedema was significantly higher with axillary node dissection plus radiation compared with axillary node dissection alone (38 versus 7 percent) [32].
Individuals undergoing breast-conserving therapy are also at risk for lymphedema following adjuvant radiation therapy. In a retrospective review involving 1497 patients (75 percent with node-negative breast cancer), the incidence of lymphedema was 7 percent [33]. For those treated with supraclavicular, axillary, and internal mammary radiation therapy, the incidences were 10, 15, and 8 percent. Factors significantly associated with an increased risk of lymphedema were:
●Pathologically involved nodes (11 versus 6 percent, if nodes were negative)
●Removal of more than 14 nodes at surgery (9.5 versus 6 percent)
●Presence of extracapsular extension (13.4 versus 6.9 percent)
●Grade 2 or 3 breast tumor (11 versus 3 percent)
●Administration of adjuvant chemotherapy (10.5 versus 7 percent)
Specific cancers
Breast cancer — Breast cancer is the most commonly reported cancer associated with lymphedema related to lymphatic dissection [20,21,34,35]. The incidence varies widely (6 to 30 percent) depending on the type of surgery, diagnostic criteria, duration of follow-up, and other factors. (See "Screening for and prevention of breast cancer-related lymphedema", section on 'Incidence and onset'.)
Surgical removal of lymph nodes (lymphadenectomy) and radiation therapy are the main causes of lymphedema in patients with breast cancer, but lymphedema can also be related to obstruction of the lymphatic channels or lymph nodes, or infiltration with tumor cells (lymphangitic carcinomatosis). Other risk factors include an invasive cancer diagnosis, local infection, and obesity, but other factors may also contribute [36,37]. The manner and timing of breast reconstruction may also play a role in the development of lymphedema [38]. (See "Screening for and prevention of breast cancer-related lymphedema", section on 'Risk factors'.)
Melanoma — Melanoma is a common cancer of the skin and can occur anywhere. The estimated incidence of lymphedema associated with melanoma is 16.3 percent overall, and 28 percent for lower extremity melanomas [23]. (See "Evaluation and management of regional nodes in primary cutaneous melanoma" and "Radiation therapy in the management of melanoma", section on 'Adjuvant RT after lymph node dissection'.)
Lower extremity lymphedema related to the treatment of melanoma is primarily due to inguinal lymph node dissection required for the treatment of the disease. However, direct nodal invasion can also result in lymphedema. The incidence of moderate lymphedema among patients who have had a total lymph node dissection has been reported to be as high as 46 percent [39]. A high incidence of 42 percent has also been reported among patients with melanoma who have undergone a deep (iliac/obturator) lymph node dissection [23]. However, the adoption of sentinel lymph node (SLN) biopsy for cancer staging (figure 6) has allowed surgeons to avoid extensive lymph node dissections, reducing the risk of lymphedema in node-negative patients. Patients with melanoma are still at risk for developing lymphedema following SLN biopsy, but the risk of lymphedema was significantly lower for patients who had SLN biopsy alone compared with lymph node dissection in a prospective assessment of 182 patients [39]. At one year following lower extremity melanoma surgery (SLN biopsy and total lymph node dissection), the overall incidence of moderate lymphedema (limb volume change >10 percent) was approximately 27 percent.
Lymphedema related to melanoma in the upper extremity can also occur. In a review of the SEER database from 2000 to 2019, melanomas occurred in the upper extremity and shoulders with at least equal frequency compared with the lower extremity and hip (25.2 and 18.7 percent, respectively) [40]. The upper extremities and shoulders were more often affected in females compared with other locations (49.2 versus 42.1 percent), whereas for males, other sites were more often affected compared with the upper extremities and shoulders (57.9 versus 50.8 percent).
Gynecologic cancers — The incidence of lower extremity lymphedema in patients with a history of gynecologic cancers is as high as 25 percent [23,41]. Treatment for gynecologic cancers often involves a combination of radiotherapy, chemotherapy, and surgical procedures. Surgical interventions that remove lymph nodes significantly increase the risk of developing lower extremity lymphedema. The risk is even higher when patients undergo postoperative radiotherapy [42]. Clinical interventions to prevent and manage postcancer lower extremity lymphedema are needed to preserve and improve the quality of life in this patient population. (See "Endometrial carcinoma: Staging and surgical treatment", section on 'Lymph node evaluation' and "Management of locally advanced cervical cancer".)
The incidence of lower extremity lymphedema varies depending on the type and stage of gynecologic cancer. In general, the incidences of lymphedema from the treatment of these malignancies are not necessarily related to the severity of the disease but rather treatment protocols. As an example, the treatment of vulvar and cervical cancer more typically includes complete inguinal lymph node dissection and radiation compared with endometrial and ovarian cancer. Treatment can include lymph node dissection and/or radiation therapy [43]. The reported incidences of lymphedema are:
●Endometrial cancer – 1 to 38 percent
●Cervical cancer – 17 to 81 percent
●Vulvar/vaginal cancer – 6 to 75 percent
●Ovarian cancer – 5 to 21 percent
Genitourinary cancers — The pooled incidence of lymphedema in patients with a history of genitourinary cancer (bladder, penile, prostate) is approximately 11 percent. The incidences of bladder, penile, and prostate cancers are approximately 16, 21, and 4 percent, respectively. (See "Radical prostatectomy for localized prostate cancer", section on 'Pelvic lymph node dissection'.)
Patients who undergo radiation therapy in addition to lymph node dissection for the treatment of genitourinary cancers are at an increased risk of developing lymphedema [23]. The observed incidence of lower extremity lymphedema is higher among patients who undergo an extended pelvic lymph node dissection (ePLND) compared with a standard pelvic lymph node dissection (sPLND) [44,45]. For the treatment of genitourinary cancers, in one review, the incidence of lower extremity lymphedema was 1.4 percent following sPLND and 8.8 percent following an ePLND [44].
Kaposi sarcoma — Kaposi sarcoma is a rare sarcoma involving the cells lining the blood and lymphatic vessels that could contribute to secondary lymphedema [46,47]. The disease is typically limited to the lower extremities, although it may be more widespread in immunocompromised patients, such as patients with acquired immunodeficiency syndrome or those who have undergone a solid organ transplant. Lymphedema may occur in this population as a result of blocked lymphatic vessels, changes in the permeability of the lymphatics, regional lymph node involvement, and increased inflammatory cytokines [48]. (See "Classic Kaposi sarcoma: Clinical features, staging, diagnosis, and treatment".)
Obesity — Obesity is an independent risk factor for lymphedema, particularly among those treated for cancer [11,26]. The effect of BMI cannot be completely separated from cancer treatment effects, in part because of potentially more difficult lymph node dissection in patients who are obese [49,50]. Patients with obesity have an increased likelihood of lymphedema following treatment for breast cancer [49,51,52]. As an example, in a study of 137 females treated for breast cancer, females with a BMI (kg/m2) >30 had a three-fold increased risk of developing lymphedema compared with those with BMI (kg/m2) <25 (odds ratio 2.93, 95% CI 1.03-8.31) [49].
BMI greater than 50 may lead to the development of lymphedema without a history of lymphatic surgery or injury (ie, obesity-induced lymphedema) [53,54]. Although the exact pathophysiology is not completely understood, obesity has been implicated in the development of lymphedema due to increased production and retention of fluid by adipose tissue [26,55,56]. Severe obesity is also associated with a clinical entity called massive localized lymphedema (pseudotumor, pseudosarcoma) [57-61]. This typically presents as a painless and longstanding lesion of the thigh (picture 1) often enlarging over many years [62]. Pathologically, it is characterized by dermal thickening and an ill-defined, unencapsulated, large mass [59,61].
Chronic venous insufficiency — Lymphedema shares many clinical features with CVI. A careful clinical evaluation can indicate if limb swelling is the result of venous inefficiency, lymphatic insufficiency, or a combination of both. (See "Clinical manifestations of lower extremity chronic venous disorders".)
Lymphedema caused by insufficiency of both the venous and lymphatic systems, which can lead to severe manifestations, is referred to by some as phlebolymphedema (PLE) (picture 2). PLE may be caused by a congenital defect of the venous and lymphatic systems or secondary to acquired CVI [25]. CVI results in an excessive fluid load at the tissue level, creating additional load to the lymphatic system. This increase in lymphatic flow may become much greater than the lymph transport capacity, resulting in lymphedema [25,63].
Infection — Infection can be both a direct cause of lymphedema and a risk factor for developing lymphedema. Early postoperative infections following lymph node dissection significantly increase the risk of lymphedema [11]. Cellulitis and infections have also been reported to increase the risk of gynecologic-related lymphedema.
Infectious causes of lymphedema are more common in tropical and subtropical regions. Parasitic infections can result in lymphatic obstruction. The most common cause of secondary lymphedema worldwide is filariasis, a disease in which parasitic worms occupy and occlude the lymphatic vessels [18,64]. As of 2018, 51 million people were infected throughout the tropics and subtropics of Asia, Africa, the Western Pacific, and parts of the Caribbean and South America. This represents a 74 percent decline since the start of the World Health Organization's Global Programme to Eliminate Lymphatic Filariasis in 2000 [65]. (See "Lymphatic filariasis: Epidemiology, clinical manifestations, and diagnosis" and "Lymphatic filariasis: Treatment and prevention".)
Beyond parasitic infections, recurrent skin infections (eg, cellulitis, erysipelas), lymphadenitis, and tuberculosis may also be complicated by the development of lymphedema [66]. (See "Approach to the adult with recurrent infections".)
Inflammatory disorders — Lymphedema is also associated with inflammatory disorders, such as arthritis, dermatitis, and sarcoidosis. Upper or lower extremity lymphedema, which can be unilateral or bilateral, is a rare extraarticular manifestation of inflammatory joint disease and is most often reported in patients with rheumatoid arthritis or psoriatic arthritis [67-73].
The mechanism of lymphedema associated with rheumatoid arthritis is not known, but inflammatory synovitis leading to fibrosis of lymph vessels has been proposed [74]. In some patients, the lymphedema improves with effective treatment of the arthritis [72-74]. (See "Overview of the systemic and nonarticular manifestations of rheumatoid arthritis", section on 'Lymphatic obstruction'.)
A similar clinical appearance is seen as a result of extensive tenosynovitis in patients with psoriatic arthritis [71]. (See "Clinical manifestations and diagnosis of psoriatic arthritis".)
Primary lower extremity lymphedema — Lymphedema that presents without an inciting factor is termed primary lymphedema [7,10,11,22]. Approximately 1 out of 6000 will develop primary lymphedema [16]. The incidence of primary lymphedema in those attending lymphedema clinics ranges from 8 percent among all newly diagnosed patients to 28 percent of those with non-cancer-related disease [13]. (See "Pathophysiology and etiology of edema in children", section on 'Primary lymphedema'.)
Primary lymphedema more frequently involves the lower extremities and the incidence is higher in females [7]. However, in one small series of 60 patients, the incidence was higher in males (2:1 male:female) [75]. The mean age at diagnosis was 38 years (range 3 to 82 years), and most cases were not associated with a recognized genetic condition.
There are many chromosomal or genetic conditions in which lymphedema is a reported feature [76]. If a genetic inheritance pattern arises without an etiology, the term familial lymphedema can be used to categorize this type of lymphedema. Some genetic disorders such as Fabry disease (Anderson-Fabry disease) may be associated with the development of lymphedema, but it is considered secondary lymphedema [77].
Extremity trauma — Injury to the lymphatic system is the cause of post-traumatic edema in 10.5 percent of patients [78,79]. Post-traumatic edema may originate from injured lymphatics, deep venous thrombosis (high risk associated with extremity trauma), or inflammation.
Traumatic injuries to the extremity that can cause damage to the lymphatic system include degloving injury (Morel-Lavallee injury), multiple fractures, and compartment syndrome. (See "Severe upper extremity injury in the adult patient" and "Severe lower extremity injury in the adult patient".)
Orthopedic surgery — In addition to surgical treatment for malignancy, the lymphatic system may become damaged during lower limb surgery. While postsurgical edema is common, total hip and total knee arthroplasty are both associated with a potential risk of developing lower extremity lymphedema [80]. (See "Total hip arthroplasty" and "Total knee arthroplasty".)
Podoconiosis — Podoconiosis is a form of lower extremity lymphedema that occurs after chronic exposure to mineral particles (silicone, aluminum, and other metals) in red clay volcanic soil. Podoconiosis, like filariasis, is a tropical lymphedema with distribution in tropical Africa, Central America, and India. It is estimated that 5 to 10 percent of barefoot populations in these regions are affected by podoconiosis. Ethiopia and Cameroon have the highest number of affected individuals (500,000 to 1,000,000 patients) [81]. Interestingly, genetic susceptibility has been shown to play a role in the development of podoconiosis, and it is associated with human leukocyte antigen variants [82]. Podoconiosis can be eliminated by wearing shoes; however, affordability of footwear or unwillingness to wear them remain barriers to use in some endemic areas [83].
Other causes — Other potential etiologies of lymphedema include thyroid dermopathy, dermatitis, and sarcoidosis [7].
SUMMARY
●Definition – Lymphedema is the abnormal accumulation of interstitial fluid and fibroadipose tissues due to abnormalities of the lymphatic system. Lymphedema develops when the lymphatic load exceeds the transport capacity of the lymphatic system. (See 'Pathophysiology' above.)
This imbalance between interstitial fluid production and transport may be due to:
•Congenital malformation of the lymphatic system
•Damage to the lymphatic vessels leading to a reduction in the number of lymph channels (eg, radiation therapy, medication effects)
•Damage or removal of lymph nodes leading to a reduction in the number of lymph nodes (eg, lymphadenectomy, trauma)
•Obstruction of the available lymphatic channels or nodes (eg, compression by a tumor)
•Infiltration of lymphatic vessels (eg, lymphangitic carcinomatosis)
●Classification – Lymphedema is classified as primary (no inciting event) or secondary lymphedema, which is much more common and due to a variety of inciting conditions. While lymphedema most commonly affects the extremities, it can also occur in other areas of the body (eg, chest, abdomen, genital region, face, neck). Primary lymphedema is categorized according to the age at which lymphedema symptoms first present as congenital lymphedema (present at birth), lymphedema praecox (age 1 to 35), and lymphedema tarda (after age 35). (See 'Etiologic classification' above.)
●Causes of secondary lymphedema – The majority of cases of extremity lymphedema are secondary and due to malignancy or its treatment. Other etiologies include the sequelae of obesity, chronic venous insufficiency (CVI), infection, inflammatory disorders, trauma including surgery, and certain environmental exposures. These are reviewed in detail above. (See 'Causes of lymphedema' above.)
