Study of the characteristics and causes of relapse amongst leprosy cases in an urban area (Calcutta).

In this retrospective study of the 3737 cases of leprosy released from treatment and followed-up during 1975 to 1990, 63 had relapsed giving an overall relapse rate of 1.69%. The relapse rate was significantly higher in the immunologically unstable N?L (Borderline) cases (2.9%). It was also higher in those who had dapsone monotherapy (1.92%) compared to those who had multidrug therapy (1.01%). The relapse rate was higher in the 10 to 29 years age group and among those who became pregnant suggesting puberty and pregnancy could be risk factors. Males had a significantly higher relapse rate (2.1%) than females (1.1%). 45.2% of relapses in N (Non-lepromatous) cases occurred within 24 months and 71.4% within 36 months of stopping treatment. In those having monotherapy, 57.1% of relapses occurred within 24 months and 76.8% within 36 months. Regularity in treatment did not seem to have much influence on relapse rates.