Objective To explore the diagnostic-therapeutic course and epidemiological characteristics of the first imported kala-azar case reported in Changning District of Shanghai, so as to provide references for early detection, timely diagnosis, and effective management of the kala-azar cases in non-epidemic areas.

Methods In 2025, a comprehensive epidemiological investigation and a complete collection of clinical records of one kala-azar patient imported from other provinces reported by a medical institution in this city were conducted. The source of infection, process of diagnosis and treatment, and clinical outcome of the case were systematically analyzed.

Results The case was a male migrant worker from Shanxi Province currently residing in Shanghai. In June 2023, the patient had a history of exposure to mosquito bites during his stay in a kala-azar endemic area. The initial onset occurred in December 2023, with clinical manifestations including unexplained fever accompanied by leukopenia, and subsequently gradually developed night sweats and fatigue during the following months. In June 2024, the patient self-perceived significant weight loss, and physical examination revealed hepatomegaly and splenomegaly, leading to a diagnosis of hemophagocytic syndrome (HPS). Throughout the whole course of the illness, the patient sought treatment at hematology departments of several hospitals multiple times, where he was managed as a case of HPS. In January 2025, a large number of Leishmania donovani were detected in the patient's bone marrow smear, confirming kala-azar. After 2 weeks of standardized treatment with amphotericin B liposomal, there was significant improvement. Combined with the epidemiological investigation, it was speculated that the incubation period of this case was about 6 months, whereas the interval from initial onset to definite diagnosis was approximately 14 months.

Conclusion Kala-azar has atypical early clinical symptoms, which are prone to confusion with HPS. For patients with recurrent unexplained fever accompanied by peripheral cytopenias, hepatomegaly and splenomegaly, medical institutions should consider the possibility of infectious diseases. Close collaboration between medical institutions and centers for disease control and prevention is essential to conduct a detailed epidemiological investigation and laboratory screening, ensuring confirmed cases receive standardized treatment.