Cutaneous Leishmaniasis: Contribution of Routine Histopathology in Unexpected Encounters

The ulcerated papules of cutaneous leishmaniasis represent an unusual form of granulomatous dermatitis caused by Leishmania species, a protozoan transmitted by sandfly bites. As the disease is not native to North America, clinical suspicion is partially based on a compatible travel history and may result in a biopsy. The key role of standard morphology is the identification of Leishmania organisms, supplemented by Giemsa and/or CD1a immunostaining. Histologically, the organism may be confused with Histoplasma species, which is resolved by staining with methenamine silver or PAS. Four cases of cutaneous leishmaniasis are presented for which organisms were present in 3; polymerase chain reaction and DNA sequencing for speciation done by the Center for Disease Control and Prevention (CDC) was confirmatory in 3 cases, including the one case without histologically identifiable organisms. Rare unexplained cases of cutaneous leishmaniasis without a travel history have been reported outside endemic areas. The present cases emphasize the importance of diagnostic awareness of unusual infections such as this in the context of political unrest, ease of international travel, climate change and the possible expansion of geographic vector distribution. In the morphologic absence of organisms, the diagnosis may require molecular techniques, currently available on a referral basis to pathologists without charge from CDC.