Clinical, Laboratory, and Therapeutic Characteristics of Visceral Leishmaniasis with Emphasis on Immune Status: A Multicentre Cohort Study in Greece.

Visceral leishmaniasis (VL) is an endemic zoonotic disease in southern Europe with increasing clinical relevance among immunocompromised populations; however, detailed clinical data remain scarce. This retrospective multicentre cohort study analysed patients with confirmed VL treated at seven hospitals in Greece over a 26-year period. Clinical, treatment, and outcome data were collected with a minimum follow-up of 18 months to assess cure, treatment failure, relapse, and mortality. A total of 144 patients were enrolled (59% male; mean age 41.8 years, range 0.1-84 years), most of whom were Greek nationals (85%) and resided in rural areas (61%). Fever was the primary reason for hospital admission in 95% of patients. At diagnosis, 42 patients (29%) were immunocompromised. These patients were significantly older than immunocompetent individuals and more likely to present with diarrhoea and arthralgia, whereas hepatomegaly was less frequent. Liposomal amphotericin B was administered to 90% of patients. Treatment failure occurred in 14 patients (10%) and was significantly associated with immunosuppression and leukaemia. Relapse within 18 months occurred in 5.5% of patients. Overall mortality was relatively low (7 patients, 5%), with one death directly attributable to VL. This study demonstrates that VL remains endemic in Greece, affects patients across all age groups, and is primarily autochthonous. Immunosuppression is associated with distinct clinical features and poorer treatment outcomes in VL, underscoring the need for heightened clinical vigilance, combined diagnostic approaches, and extended follow-up in vulnerable populations.