Leishmania (Viannia) lainsoni occupies a unique niche within the subgenus Viannia.

Leishmania lainsoni has recently been recognized as a new peripylarian species belonging to the subgenus Viannia and the L. braziliensis complex. It has been isolated from its sandfly vector, reservoir host and cutaneous lesions of human patients. Microscopical examination has shown characteristics which are different from those of other members of the L. braziliensis complex. Nuclear deoxyribonucleic acid (DNA) hybridization patterns with a beta tubulin probe and kinetoplast DNA buoyant density measurements show close similarities with other species of the L. braziliensis complex. However, kinetoplast DNA restriction enzyme fragment patterns of L. (V.) lainsoni isolates show similarities to L. mexicana complex species as well as weak cross hybridization. L. (V.) lainsoni is also amplified with L. braziliensis complex specific polymerase chain reaction (PCR) primers but it requires a lower annealing temperature and gives a 300 base pair PCR product. A possible model for the binding of PCR primers to the L. (V.) lainsoni kinetoplast DNA minicircle is proposed.