Comments in response to report on ‘Late reversal reaction with resistant Mycobacterium leprae : an emerging paradigm’

We have read with interest the case report by Sardana et al. ‘Late reversal reaction with resistant Mycobacterium leprae: an emerging paradigm’. ¹ We agree with the authors as far as drug resistant M. leprae and its association with recurrent reactions is concerned. We have a difference of opinion about the diagnosis of type 1 reaction/reversal reaction in the index case.

The patient was diagnosed as lepromatous leprosy (LL) and after completion of multidrug treatment (MDT) presented with clinical features of sudden onset of painful, erythematous nodular lesions, distributed all over the body with histopathology showing oedema and foamy cell infiltrate and rapid response to oral steroids. We are of the opinion that this is a case of erythema nodosum leprosum (ENL) type-II reaction which occurs more frequently in multibacillary disease and can occur even 8–10 years after release from treatment (RFT). ² Moreover, a bacillary index (BI) of 3 + noted at the time of onset of reaction is a risk factor for the development of ENL. Recurrent ENL after RFT in lepromatous spectrum of disease is not uncommon and the average fall in BI is about 1 log/year after successful MDT, though no information is available about BI at the start of MDT or RFT in the index case. The authors have mentioned that the patient had complete clearance of lesions after 12 months of MDT, which is again unusual as the infiltration in cases of LL seldom clears completely after one year of MDT multibacillary regime (MBR), and if this case had rifampicin resistance, then it is unlikely that his lesions will clear and he will remain asymptomatic for two years after completion of treatment.

The reason for conducting viability and drug resistance testing in the index case is also not clear, as late reactions are known to occur in cases with high bacillary load and the patient had responded favourably to prednisolone. Moreover, the index case did not even have recurrent or chronic reactions which may be seen in patients harbouring drug-resistant bacilli. The authors have mentioned that polymerase chain reaction showed 1.54 × 10² viable bacilli. Readers will also be interested to know more details about this figure, its significance and implication after ‘successful MDT’ in this case and what this number conveys: is it per grams or micrograms of skin tissue?

The authors have hypothesised that the index patient probably had secondary resistance to rifampicin. This was based on the premise that in primary resistance, multiple doses of rifampicin would select the resistant strains and this would result in clinical deterioration of the disease, which did not occur; instead, the index patient had clinical resolution of disease at the end of the treatment.

We have also observed that a subset of patients with high BI continue to suffer from recurrent and chronic ENL. Drug resistance testing followed by appropriate anti-leprosy treatment helps in bacillary clearance as well as resolution of chronic ENL in these patients. ³ Unfortunately, the facilities for drug resistance testing in leprosy are available at only few referral and research laboratories; however, if it is done in time, it might prevent the patient from experiencing the adverse effects of prolonged immunosuppression given for chronic type 2 lepra reactions. We do acknowledge the fact that since this patient was found to have rifampicin resistance, there is a need for guidelines to be established to decide which patients require drug resistance testing in the setting of limited resources.