Erythema nodosum is an uncommon reaction pattern seen mainly on the anterior tibial areas of the legs. It appears as erythematous nodules in successive crops and is preceded by fever, malaise, and arthralgia.
PRIMARY LESIONS. Bilateral red, tender, rather well-circumscribed nodules are seen mainly on the pretibial surface of the legs but also on the arms and the body. Later, the flat lesions may become raised, confluent, and purpuric. Only a few lesions develop at one time.
SECONDARY LESIONS. The lesions never suppurate or form ulcers.
COURSE. The lesions last several weeks, but the duration can be affected by therapy directed to the cause, if it is known. Relapses are related to the cause. It can be idiopathic and have a chronic course.
CAUSES. Careful clinical and laboratory examination is necessary to determine the cause of this toxic reaction pattern. The following tests should be performed: complete blood cell count, erythrocyte sedimentation rate, urinalysis, serologic test for syphilis, chest roentgenogram, and specific skin tests, as indicated. The causes of erythema nodosum are streptococcal infection (rheumatic fever, pharyngitis, scarlet fever, arthritis), fungal infection (coccidioidomycosis, trichophyton infection), pregnancy, sarcoidosis, lymphogranuloma venereum, syphilis, chancroid, drugs (contraceptive pills, sulfonamides, iodides, bromides), and, rarely, tuberculosis.
AGE AND SEX INCIDENCE. The disorder occurs predominantly in adolescent girls and young women.
LABORATORY FINDINGS. Histopathologic examination reveals a nonspecific but characteristically localized inflammatory infiltrate in the subcutaneous tissue and in and around the veins.
Erythema induratum: Chronic vasculitis of young women that occurs on the posterior calf area and often suppurates; biopsy shows a tuberculoid-type infiltrate, usually with caseation. A tuberculous causation has been suggested, again.
Necrobiosis lipoidica diabeticorum: An uncommon cutaneous manifestation of diabetes mellitus, characterized by well-defined patches of reddish-yellow atrophic skin, primarily on anterior areas of legs; the lesions can ulcerate; biopsy results are characteristic, but biopsy is usually not necessary or indicated because of the possibility of poor healing (see Ch.ap...2§).
Periarteritis nodosa: A rare, usually fatal arteritis that most often occurs in males; 25% of patients show painful subcutaneous nodules and purpura, mainly of the lower extremities. There is a cutaneous variety.
Nodular vasculitis: Chronic, painful nodules of the calves of middle-aged women, which rarely ulcerate and recur commonly; biopsy is of value; this disorder may be a chronic variant of erythema nodosum.
Superficial thrombophlebitis migrans of Buerger's disease: An early venous change of Buerger's disease commonly seen in male patients, with painful nodules of the anterior tibial area; biopsy is of value.
Nodular panniculitis or Weber-Christian disease: Occurs mainly in obese middle-aged women; tender, indurated, subcutaneous nodules and plaques are seen, usually on the thighs and the buttocks; each crop is preceded by fever and malaise; residual atrophy and hyperpigmentation occur.
Leukocytoclastic vasculitis: Includes a constellation of diseases, such as allergic angiitis, allergic vasculitis, necrotizing vasculitis, and cutaneous systemic vasculitis. Clinically, palpable purpuric lesions are seen, most commonly on the lower part of the legs. In later stages, the lesions may become nodular, bullous, infarctive, and ulcerative. Various etiologic agents have been implicated, such as infection, drugs, and foreign proteins. Treatment includes bed rest, pentoxifylline (Trental), and corticosteroids (see Chap 10).
For completeness, the following five very rare syndromes with inflammatory nodules of the legs are defined in the Dictiona^ry-jndex: (1) subcutaneous fat necrosis with pancreatic disease, (2) migratory panniculitis, (3) allergic granulomatosis, (4) necrobiotic granulomatosis, and (5) embolic nodules from several sources.
1. Treat the cause, if possible.
2. Rest, local heat, and aspirin are valuable. The eruption is self-limited if the cause can be eliminated.
3. Chronic cases can be disabling enough to warrant a short course of corticosteroid therapy. Some cases have benefited from naproxen (Naprosyn), 250 mg b.i.d. (or other nonsteroidal antiinflammatory drugs), for 2 to 4 weeks.
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