A Forgotten Foe Returns: The Diagnostic Odyssey of Kala-Azar Masquerading as Myelodysplastic Syndrome in a Post-Elimination Era.

We report a diagnostically complex case of visceral leishmaniasis (Kala-azar) in a 73-year-old male from a country where the disease was eliminated in 2023. The patient presented with a 2-month history of low-grade fever, fatigue, progressive skin hyperpigmentation over 2 years, and hepatosplenomegaly. Initial investigations revealed pancytopenia (hemoglobin 10.4 g/dL, white blood cells 3500/mm3, platelets 60,000/mm3), prompting a differential diagnosis of Kala-azar versus myelodysplastic syndrome (MDS). The rapid diagnostic test (rK39) for Kala-azar was positive, but bone marrow examination showed dysplastic changes, hypercellularity, decreased myeloid-erythroid ratio, binucleate erythrocytes, and maturation arrest at the myelocyte stage without Leishmania donovani (LD) bodies, complicating the diagnosis. Financial constraints precluded fluorescence in situ hybridization (FISH) testing for MDS confirmation. Repeated peripheral blood film (PBF) and rK39 testing (qDetect Kala-azar) on February 6, 2025, confirmed Kala-azar, ruling out MDS as the primary pathology. The patient responded well to liposomal amphotericin B treatment (3 mg/kg/day according to WHO regimen). This case underscores the challenge of diagnosing Kala-azar in post-elimination settings, particularly when clinical and laboratory features overlap with hematological disorders like MDS. It highlights the critical need for persistent diagnostic evaluation, including repeated serological and hematological testing, to differentiate infectious causes from malignancies in patients with unexplained pancytopenia. Clinicians must remain vigilant for re-emerging infectious diseases, even in regions where they are deemed eliminated, to ensure accurate diagnosis and prompt treatment, ultimately improving patient outcomes in resource-limited settings.