Snapshot A 35-year-old man presents to the dermatology clinic for a rash. He reports that these spots have been on his skin for about 2 months now since he returned from a work-stay program in South America. There he interacted with animals and occasionally tried exotic foods, such as the armadillo. On physical exam, there are multiple well-circumscribed erythematous plaques with raised borders and central hypopigmentation. There is loss of sensation over the plaques. He is started on a long course of antibiotics. Introduction Classification Mycobacterium leprae a non-motile, acid-fast bacillus prefers cool temperatures transmission respiratory via nasal mucosa via armadillo reservoirs Epidemiology incidence more common in Southeast Asia and South America location affects skin and peripheral nerves risk factors travel to endemic countries contact with others with leprosy contact with or consumption of reservoirs such as armadillos Pathogenesis the bacteria grows in cool regions, such as the skin and peripheral nerves infects macrophages, Schwann cells, and keratinocytes lepromatous Hansen disease weak cell-mediated immunity humoral Th2-type immune response high burden of bacteria in lesions tuberculoid Hansen disease strong cell-mediated immunity Th1-type immune response low burden of bacteria in lesions Associated conditions lepromatous Hansen disease tuberculoid Hansen disease erythema nodosum Prognosis slow progression that may develop over months or years may have intermittent acute leprosy reactions lepromatous type is more severe Presentation Symptoms lepromatous Hansen disease diffuse rash tuberculoid Hansen disease multiple discrete lesions Physical exam patients often present with overlapping findings peripheral neuropathy foot drop facial nerve palsy contractures or hand or feet loss of sensation lepromatous Hansen disease leonine facies (lion-like) thickened foreheard, ears, eyebrows, and cheeks diffuse plaques and nodular skin lesions symmetrically distributed may be erythematous or hypopigmented without sharp borders tuberculoid Hansen disease multiple discrete erythematous plaques with central hypopigmentation and raised discrete borders plaques often have loss of sensation hairless dry with some scale Studies Labs tissue polymerase chain reaction (PCR) may test as falsely positive on VDRL testing Biopsy or slit-skin smear acid-fast bacilli granulomas Making the diagnosis based on clinical presentation and tissue diagnosis Differential Morphea distinguishing factor also presents with thickened skin but usually does not involve peripheral nerve damage Vitiligo distinguishing factor also presents with hypopigmentation but without peripheral nerve damage or raised borders Treatment Medical dapsone and rifampin indication tuberculoid and lepromatous types clofazimine indication added therapy for lepromatous types Complicatons Permanent nerve impairment Deformities