In most cases the diagnosis of primary or secondary lymphedema can be made, and the condition differentiated from other causes of a swollen limb, on the basis of history and examination without recourse to complex investigation. Unlike other types of edema, lymphedema characteristically involves the foot. The contour of the ankle is lost through infilling of the sub-malleolar depressions; a "buffalo hump" forms
on the dorsum of the foot, the toes appear square due to confinement of footwear, and the skin on the dorsum of the toes cannot be pinched due to subcutaneous fibrosis (Stemmer's sign). Lymphedema usually spreads proximally to knee level and less commonly affects the whole leg. In the early stages, lymphedema "pits," and the patient reports that the swelling is down in the morning. This represents a reversible component to the swelling, which can be controlled. Failure to do so allows fibrosis, dermal thickening, and hyperkeratosis to occur. In general, primary lymphedema progresses more slowly than secondary lym-phedema. Chronic eczema, fungal infection of the skin (dermatophytosis) and nails (ony-chomycosis), fissuring, verrucae, and papillae (warts) are frequently seen in advanced disease. Ulceration is unusual except in the presence of chronic venous insufficiency.
Lymphangiomas are dilated dermal lymphatics that blister onto the skin surface. The fluid is usually clear but may be blood stained, and in the long term they thrombose and fibrose, forming hard nodules, raising concerns about malignancy. If they are <5 cm across, they are termed lymphangioma circumscriptum; if more widespread, lymphangioma diffusum. If they form a reticulate pattern of ridges, they are termed lymphedema ab igne. Lymphangiomas frequently weep (lymphorrhea, chylorrhea), causing skin maceration and act as a portal for infection. Protein-losing diarrhea, chylous ascites, chylothorax, chyluria, and discharge from lymphangiomas suggest lymphangiectasia (megalymphatics) and chylous reflux.
Ulceration, nonhealing bruises, and raised purple-red nodules should lead to suspicion of malignancy. Lymphangiosarcoma was originally described in postmastectomy edema (Stewart-Treves syndrome) and affects about 0.5% of patients at a mean onset of 10 years. However, lymphangiosarcoma can develop in any long-standing lymphedema but usually takes longer to manifest (20 years). It presents as single or multiple bluish/red skin and subcutaneous nodules that spread to form satellite lesions that may then become confluent. The diagnosis is usually made late, and confirmed by skin biopsy. Amputation offers the best chance of survival, but even then most patients live less than 3 years. It has been suggested that lymphedema leads to an impairment of immune surveillance and so predisposes to other malignancies, although the causal association is not as definite as it is for lymphangiosarcoma.
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