A single skin lesion--an unusual presentation of lepromatous leprosy.

Lepromatous leprosy presenting as a solitary lesion with a high bacterial count is a rare occurrence. Such a case has been followed at the National Hansen's Disease Center, Carville, Louisiana, U.S.A., since 1977. The lesion was located on the left elbow and had been present for about nine months. The bacterial index in the lesion was 5+ and the morphological index was 0%, but slit-skin smears elsewhere were negative. The histopathology of the lesion was that of subpolar lepromatous leprosy, and the lepromin skin test was negative. Growth of the organism in the mouse foot pad was characteristic of Mycobacterium leprae, and the patient's response to dapsone monotherapy has been excellent. Therefore, this patient with a single skin lesion has lepromatous leprosy histologically, immunologically, and bacteriologically. This case illustrates the importance of slit-skin scrapings and biopsy in new cases with unusual lesions and, secondly, suggests that there are factors yet undetermined which play a significant role in determining host response to M. leprae.