Post-kala-azar dermal leishmaniasis: a global overview

Post-kala-azar dermal leishmaniasis (PKDL) is a chronic dermal sequela in apparently cured patients with visceral leishmaniasis (VL). It presents with either macular or polymorphic forms, and poses a major epidemiological challenge in South Asia, particularly in India, Bangladesh and Nepal. Although nonfatal, PKDL acts as a reservoir for Leishmania donovani, thereby sustaining transmission in the postelimination phase of VL. Potential risk factors for PKDL include a history of VL, immunosuppression, host genetics and malnutrition. The disease burden is further complicated by poor health-seeking behaviour and stigma associated with dermal lesions, leading to diagnostic delays and under-reporting. PKDL is associated with a mixed T helper 1/2 profile, translating into a mixed anti-inflammatory/regulatory and proinflammatory milieu. This is coupled with prominent infiltration of immune cells into lesional sites, including macrophages, lymphocytes and neutrophils, which cause 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 noncompliance. Overall, the integration of molecular diagnostics, immunological insights and community-based treatment strategies are essential to eliminate PKDL and sustain efforts to eliminate kala-azar.