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This 90-year-old asymptomatic woman was found living under a bridge. She was unable to supply a reliable medical history.
Hansen’s disease, lepromatous type. The patient’s facial nodules and plaques, coupled with nodules on her arms and neck, immediately suggested leprosy. A biopsy specimen from a nodule on her arm showed numerous acid-fast organisms in clusters (image below). The rest of her physical examination and results of routine laboratory tests were unremarkable. Subsequently, the patient was transferred to the U.S. Public Health Service Hospital, Carville, Louisiana, for long-term management.
Patients with lepromatous leprosy have no cell-mediated immunity to the causative agent, Mycobacterium leprae. Consequently, they have diffuse disease, with many lesions containing large numbers of bacteria. By contrast, patients with tuberculoid leprosy have a high degree of cell-mediated immunity to M leprae. As a result, they have localized disease with one or two skin lesions and relatively few bacteria.
One final point. The incubation period for leprosy is uniquely long among bacterial diseases, with a minimum of two to three years, an average of five to seven years, and a maximum of 40 to 50 years.