Multibacillary leprosy with an incubation period exceeding 50 years

Leprosy is a chronic granulomatous infection predominantly involving the skin and peripheral nervous system. The condition is caused by infection with the obligate intracellular bacillus Mycobacterium leprae and the clinical phenotype is largely dependent on the host immune response to the organism. Transmission is suspected to occur via respiratory secretions with infection usually requiring prolonged periods of contact. The incubation period is highly variable with disease manifestations appearing up to several decades after the initial exposure. The disease can be broadly divided into 'paucibacillary' and 'multibacillary', and treatment with multidrug therapy including dapsone, clofazimine and rifampicin offers high rates of cure. Here, we report of a case of leprosy with a suspected incubation period in excess of 50 years following occupational exposure in rural Australia. To our knowledge, this incubation period is the longest reported to date.