Micropathological changes in the sub-epidermal zone of normal appearing skin in leprosy

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 the hematogenous spread, especially in lepromatous cases. The micropathological changes in epidermis, nerves and skin appendages from lesioned skin reported by various authors but reports of involvement of apparently normal sites are few. We investigated skin biopsy material taken from 130 patients with clinically diagnosed leprosy. Biopsies were taken at least 10 cm away from site of lesion. 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 were indeterminate in 53 cases (40.8%), tuberculoid in 29 cases (22.3%), borderline tuberculoid in 14 cases (10.8%), borderline leprosy in ten cases (7.7%), borderline lepromatous in nine cases (6.9%) and lepromatous leprosy in 15 cases (11.5%). The changes were seen in sub-epidermal zone of normal appearing skin in all type of leprosy, but involvement was greater at the lepromatous end of the spectrum compared to tuberculoid end. Acid-fast bacillus (AFB) was seen in subepidermal zone of normal appearing site. Presence of AFB is significant as far as dissemination and transmission of disease is concerned.