S-100 protein in the diagnosis of tuberculoid borderline tuberculoid leprosy

Background: A definitive diagnosis of tuberculoid and borderline tuberculoid leprosy is based on a demonstration of either acid-fast bacilli or nerve elements within the granulomas. On routine hematoxylin and eosin stains, the nerve fibers are not easily identifiable. In this study, we used S-100 protein to highlight the nerve elements and to count their numbers in leprosy and non-leprosy granulomas. Materials and Methods: Skin biopsy specimens from 15 cases of wuberculoid/borderline tuberculoid leprosy and 14 cases belonging to other granulomatous diseases of the skin were stained with S-100 protein. The surface area of all the biopsies was calculated and the number of nerve bundles stained with S-100 protein were counted in each specimen. Results: The nerve bundles were 15 per cm(2) in leprosy cases, and 9.2. per cm(2) in non-leprosy cases. In addition, the leprosy cases showed longer nerve twigs that were perpendicularly oriented to the skin surface. Conclusion: Immunostaining with S-100 facilitated detection of nerve elements in tuberculoid/borderline tuberculoid leprosy. Also, an increased number of nerve elements were found in leprosy granulomas when compared with non-leprosy granulomas (P=<0.05).