A comparative evaluation of skin and nerve histopathology in single skin lesion leprosy.

Background: In spite of leprosy being a disease of nerves, ROM therapy for single skin lesion leprosy was based on clinical trials without much evidence-based studies of nerve pathology. The present study was undertaken to compare the histology of skin and nerve in single skin lesion leprosy, and to assess the scientific rationale and justification of single dose ROM therapy.

Methods: Twenty-seven untreated patients with single skin lesion without significantly thickened peripheral nerves were selected. Skin and nearby pure cutaneous nerve biopsies were studied under both H&E and Fite's stain.

Results: All the skin biopsies were negative for AFB and clinico-pathological correlation was positive in 51.85% of skin biopsy specimens. Histopathological diagnosis of leprosy was evident in 55.5% of clinically normal looking nerves, with AFB positivity in 29.6% of nerve biopsy specimens. Correlation between clinical diagnosis and nerve histopathology was poor (26%).

Conclusions: Single skin lesion without thickened peripheral nerves as criteria for single dose ROM therapy is not logical, since the histological diagnosis of leprosy in normal looking nerves with presence of AFB is revealed in this study. Pure cutaneous nerve biopsy is a simple outpatient procedure, without complications. This study emphasizes the need to consider nerve pathology as an important tool for further therapeutic recommendations, than just clinical trials and skin pathology alone. Though single dose ROM therapy has been withdrawn recently, the principle holds good for any future therapeutic recommendations.