Post-kala-azar dermal leishmaniasis (PKDL) is a sequela of treated visceral leishmaniasis (VL). Also known as dermal leishmanoid, PKDL presents primarily as a chronic skin rash. However, the condition may sometimes be seen in patients who have never had clinical VL.

VL, or kala-azar (meaning "black fever" in Hindi), is a systemic protozoal disease that is caused by Leishmania donovani or Leishmania infantum. The majority of cases of VL are found in the following areas of the world: Eastern India, Nepal, Bangladesh, Ethiopia, Sudan, South Sudan, and Brazil. The disease is transmitted by the bite of an infected sandfly. The parasite exists in 2 forms: the amastigote form (in humans) and the promastigote form (in sandflies). The amastigote form is a round or oval structure that contains a nucleus and a DNA-containing body called the kinetoplast.

Geographic areas where PKDL is most prevalent are East Africa (especially Sudan) and South Asia (mainly Eastern India and Bangladesh). A subset of patients who receive treatment for VL go on to develop PKDL months or years after treatment. Interestingly, PKDL develops primarily in those cases of treated VL caused by L. donovani, not L. infantum.

There seems to be a variance in presentation in different areas of the world. In Sudan, the lesions generally appear within 6 months of treatment in approximately 50%-60% of cases of VL and last for a few months to about a year. In contrast, PKDL in India manifests later (1-2 years after treatment), may persist for much longer (even up to 20 years), and develops in only about 5%-10% of patients treated for VL.

The pathogenesis of the disease is not clear, and why only a subset of patients develop PKDL is not known. Studies have shown that this is an immune-mediated process. Certain risk factors associated with the development of PKDL are suboptimal treatment of VL, young age, HIV infection, and antiretroviral treatment.