[Etiology of erythema nodosum in rheumatology outpatient clinic].

Erythema nodosum (EN) is a skin lesion presenting with the acute appearance of red nodular eflorescences caused by a reactive immunological process. In most cases EN regresses spontaneously within 3 to 6 weeks and often recurs. This paper is based on a sample of 98 patients from Croatia which were treated in a rheumatologic outpatient clinic by the same internal medicine and rheumatology specialist. Presentation and differences between secondary and idiopathic forms of EN in the Croatian population were analyzed. The results show the final proportion of EN associated with secondary etiology as 47/98. Secondary etiology of EN included mostly infectious diseases (23/98), sarcoidosis (18/98) and IBD (4/98). Comparison of various clinical and laboratory parameters of both idiopathic and secondary EN resulted in a small number of statistically significant differences found (sore throat, recent respiratory infections, ASO titer changes, antibiotics use). The conclusion is that the approach to patients with EN starts by a careful taking of patient history, with an emphasis on recent upper respiratory tract infections and occurrence of diarrhea. A thorough physical examination, basic hematological and biochemical tests, basic inflammatory markers (ESR, CRP), chest X-ray and PPD test are required to determine which patients need further evaluation. A throat swab and/or determination of the titer ofASO on two occasions at intervals of 2-4 weeks should be done. It is important to perform regular patient follow-up. Considering literature substantiated regional differences in the etiology of EN it is recommended that for each population the prevalence of individual causes of EN is determined and the clinical approach accordingly standardized.