ENL reactions in the multibacillary cases of the AMFES cohort in central Ethiopia: incidence and risk factors.

Erythema nodosum leprosum (ENL), or type 2 leprosy reactions are an important complication of multibacillary leprosy. The AMFES cohort includes 300 new multibacillary cases that have been followed for up to 10 years from the start of treatment, in central Ethiopia. Sixteen (5.3%) patients had ENL reactions. The incidence of ENL was maximal in the second and third years after the start of treatment, reaching 6.9 episodes per 100 person years at risk. Factors associated with being lepromatous [LL classification and a high bacillary index (BI)] gave an increased risk of developing ENL; in the univariate analysis, LL classification gave a relative risk of 3.6 (95% CI 1.3-10) and a BI of 6 gave a relative risk of 8.6 (95% CI 2.3-32) for the development of ENL. HIV co-infection was found to be a risk factor in this cohort, but as the numbers involved are small (only two HIV positive patients had ENL), this finding must be confirmed in larger studies. Ten of the 16 cases had recurrent episodes and five had at least five episodes occurring over a period of more than 2 years. The management and prognosis of ENL reactions are discussed.