Erythema nodosum. Red, tender, subcutaneous nodules on the extensor aspects of the legs between knees and ankles are a common condition of many causes, some clear, some likely, and many obscure. The most important conditions that are heralded or attended by erythema nodosum are such infections as streptococcal upper-respiratory infections, ulcerative colitis, histoplasmosis, coccidioidomycosis, tuberculosis, syphilis, and leprosy. Another condition that is sometimes revealed by investigation of erythema nodosum is sarcoidosis. Drugs, including oral contraceptives, appear to be the cause of particular cases of erythema nodosum. In many cases, however, no clear cause can be found.
Color Atlas of Pediatric Dermatology
Samuel Weinberg, Neil S. Prose, Leonard Kristal
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