Histopathologic evidence to show that indeterminate leprosy may be a primary lesion of the disease.

Five biopsies of patients with indeterminate leprosy and five with skin lesions of nonspecific chronic inflammation were chosen. Histopathologic changes in the presence of acid-fast bacilli (AFB) in an average number of 145 serial sections from the entire paraffin block from each were evaluated. In all five indeterminate lesions AFB were found in the dermis, but intraneural AFB were present in only two cases. Mainly, lymphocytic infiltrate was present in two and early, poorly formed granulomas were seen in three. It is suggested that nonspecific chronic inflammation of the skin could precede indeterminate disease and that AFB, before they entered the dermal nerves, may be found in other dermal tissues. In most if not all early lesions of indeterminate leprosy Mycobacterium leprae would be found if an adequate number of sections stained for AFB were examined. The histopathologic and immunologic features of indeterminate disease were in favor of it being a primary lesion in leprosy.