ETIOLOGY
The exact character and the cause of erythema nodosum have not been finally established. Opinion is divided between three suppositions; namely, that erythema nodosum is a manifestation of rheumatic fever; that it is a tuberculous manifestation or that it is an independent and separate disease probably of an acute infectious character.
The opinion that erythema nodosum is related to rheumatic fever has few supporters. Acknowledged differences in the manifestations of these diseases make it improbable that they are closely related. Koch1 noted that 76 per cent of his cases occurred during the first six months and 24 per cent during the last six months of the year. In contrast to this, 52 per cent and 48 per cent of cases of rheumatic fever occurred in the corresponding periods. Thus erythema nodosum has a definite seasonal occurrence, which is not a feature of rheumatic fever. In none of