Clinical, histopathological and bacteriological study of 52 referral MB cases relapsing after MDT.

Fifty-two BB-LL relapse cases referred to our centre during 1997-2003 were investigated in detail. Twenty-four cases had been treated with extended MB-MDT [until smear negativity (NON-FDT)]. The remaining 28 cases (54%) had received one of the fixed duration regimens (FDT), of whom 11 had 24 months and 6 had 12 months of WHO MB-MDT. Eleven cases had received rifampicin/ofloxacin (RO) treatment. Follow-up slit skin smear reports were available for 41 cases, all but three cases had been smear negative at some point after release from treatment. None of the cases showed any clinical or bacteriological evidence of upgrading, i.e. LL to BT where as downgrading BB to BL occurred in five cases. The duration between cessation of treatment and reappearance of lesions (DCTR) varied from 2 to 15 years. The mean DCTR was longest (9.4 years) for the NON-FDT and 24 months MB-MDT cases. The mean DCTR was significantly lower in the 12 months MB-MDT and RO treated cases (6.8 and 6.2 years, respectively). Four of RO treated cases and four cases with multiple episodes of reaction had DCTR less than 5 years. Inadequate treatment/poor killing of Mycobacterium leprae results in early onset relapse, whereas 'persisting' or 'drug resistant mutants' contribute to late onset relapse.