The distribution of Mycobacterium leprae in the hair follicle of the eyebrow.

Longitudinal sections of hair follicles from the eyebrows of patients with active, untreated, lepromatous leprosy were studied. Mycobacterium leprae were found in the dermal papilla and outer root sheath of both anagen and telogen hair follicles. Bacilli were rarely found in those cell lines continuous with the environment, i.e., the hair shaft and the inner root sheath. The biochemical fate of these cell lines is such that they would not provide a suitable medium for the survival and transport of bacilli into the environment. We conclude that it is unlikely that the hair follicle plays a significant role in the dissemination of M. leprae but it may be important in providing a suitable site for the incubation of the bacillus within the dermis.