Histopathological changes in the arrector pili muscle of normal appearing skin in leprosy patients

Leprosy is a chronic inflammatory disease caused by Mycobacterium leprae, which affects not only the peripheral nerves and skin, but also various internal viscera through hematogenous spread, especially in lepromatous cases. Histology in its own way plays a vital role, not only in classifying the established lesion, but also in confirming the clinical diagnosis. During the latent period of subclinical involvement, the apparently normal looking skin might also be undergoing some pathological changes.

We investigated skin biopsy material taken from 60 patients with clinically diagnosed leprosy at Subharti Hospital, Subharti Medical College, Meerut, India. Hematoxylin and eosin staining and Harada's modified allochrome method for acid-fast bacilli were applied for histological investigations.

The pattern of leprosy among the patients was indeterminate in 25 cases (41.7%), tuberculoid in 14 (23.3%), borderline tuberculoid in six (10%), borderline leprosy in four (6.7%), borderline lepromatous in four (6.7%), and lepromatous leprosy in seven (11.7%). Changes were seen in the arrector pili muscle of normal appearing skin in all types of leprosy, but involvement was greater at the lepromatous end of the spectrum compared to the tuberculoid end.

Results of this study revealed definitive histological changes in the arrector pili muscle in normal appearing skin. The presence of AFB is significant as far as dissemination and transmission of the disease is concerned.