Lepromatous leprosy: an elusive mimicker mistaken for polyarteritis nodosa and disseminated tuberculosis

Leprosy is a chronic infectious disease caused by the obligate intracellular microorganism, Mycobacterium leprae and presents as skin lesions and peripheral neuropathies with upper respiratory mucosa involvement. We present a case of a 36-year-old immunocompromised female whom was recently diagnosed polyarteritis nodosa vasculitis (PAN) in Trinidad and returned back to the US with a two week history of pleuritic chest pain, fever, chills, fatigue, nausea, vomiting, epistaxis and cough.  Physical examination revealed a diffuse rash. Pancytopenia prompted a bone marrow biopsy, which revealed acid-fast bacteria, suspicious for disseminated tuberculosis. Histologic examination of the skin lesions revealed disseminated acid-fast, Fite-positive microorganisms within the dermis and nerves. She developed anuric renal failure and purpura fulminans with disseminated intravascular coagulation (DIC). PCR results from the skin sample shortly thereafter revealed the presence of M. leprae DNA. Mycobacterium tuberculosis complex DNA was not identified. This case demonstrates an unusual presentation of leprosy with bone marrow involvement and highlights the importance of utilizing histologic examination together with molecular diagnostic techniques to aid in establishing the correct diagnosis and treatment. This case also cautions that leprosy can be misdiagnosed as a vasculitis, specifically PAN, as there is overlap in the clinical presentation of each disease and that clinicopathologic correlation is essential.