Etiology of erythema nodosum.

One hundred patients with biopsy-proven erythema nodosum were studied at Ramathibodi Hospital from 1982 to 1992 to find out the etiology of this disease. Eighty-eight were females while twelve were males, with an age range from 6 to 72 years old (mean, 31 years old). Abnormal laboratory findings in these patients included elevation of erythrocyte sedimentation rate (76.9%), increase anti-streptolysin-O titer (10.7%), abnormal chest roentgenogram (16.7%), positive tuberculin test (50%). The cause of erythema nodosum is still unknown in a large group of patients, and it was found only in twenty-eight patients (28%). Twelve patients had tuberculosis, seven had history of antibiotic administration, six probably had streptococcal infection and the other three had Behcet's disease.