Diagnostic value of histopathology of the affected nerve versus overlying skin, in pure neural cases of leprosy

Proof of leprosy as a cause of ‘pure neural leprosy’ needs histological evidence, which is often sought in the affected peripheral nerves. Obtaining a nerve biopsy may not always be practicable. Thus in this study, the histopathology of the involved nerve and the overlying skin were compared in 32 cases of ‘pure neural leprosy’ in order to determine the utility of skin biopsy in diagnosing leprosy. Evidence of leprosy was present in all, except one nerve biopsy (97%) and in 14/32 (44%) skin biopsies from skin overlying the biopsied nerve. One noteworthy finding is that in nerves showing BL-LLs leprosy, which formed a major group (59%), only 26% of biopsies of the overlying skin showed evidence of leprosy. In nerves showing BT pathology, 67% of the biopsies of overlying skin showed evidence of leprosy. Conclusion: Histopathological examination of the overlying skin compares poorly with the affected cutaneous nerve and is of limited diagnostic value, particularly at the lepromatous end of the spectrum.