Post-kala-azar dermal leishmaniasis: a global overview

Post-kala-azar dermal leishmaniasis (PKDL), a chronic dermal sequela, in apparently cured visceral leishmaniasis (VL) patients present with either macular or polymorphic forms, and poses a major epidemiological challenge in South Asia, particularly India, Bangladesh, and Nepal. Although non-fatal, PKDL acts as a reservoir for Leishmania donovani, thereby sustaining transmission in the post-elimination phase of VL. Potential risk factors for PKDL include a history of VL, immunosuppression, host genetics and malnutrition, and the disease burden is further complicated by poor health-seeking behaviour and stigma associated with dermal lesions, leading to diagnostic delays and underreporting. PKDL is associated with a mixed Th1/Th2 profile, translating into a mixed anti-inflammatory/regulatory and pro-inflammatory milieu, coupled with prominent immune cellular infiltration into lesional sites, including macrophages, lymphocytes, and neutrophils, that caused localized immune alteration. The diagnosis of PKDL is challenging in macular cases due to their low parasite burden and overlapping symptoms with other hypopigmentary disorders, but molecular tools now offer improved sensitivity and even have field-level applicability. In terms of therapeutics, the management of PKDL is hindered by the need for prolonged treatment, chances of relapse, emerging drug resistance, and non-compliance. Overall, the integration of molecular diagnostics, immunological insights, and community-based treatment strategies are essential to eliminate PKDL and sustain kala-azar elimination efforts.