Complex Investigation of a Pediatric Haematological Case: Haemophagocytic Syndrome Associated with Visceral Leishmaniasis and Epstein–Barr (EBV) Co-Infection

Background: Visceral leishmaniasis (VL) is an anthropozoonosis caused by an intracellular parasite belonging to the genus Leishmania. In the Mediterranean region, L. donovani and L. infantum are responsible for VL and dogs are the main reservoir. Haemophagocytic lymphohistiocytosis (HLH) represents a complication of VL and consists of unrestrained activation and proliferation of lymphocytes and macrophages, leading to uncontrolled immune activation. Haemophagocytic lymphohistiocytosis may also develop during viral infection, and Epstein–Barr virus (EBV) infection is one of the main HLH causes. Macrophage haemophagocytosis in the bone marrow aspirate is pathognomonic. Case presentation: The case involves a 19-month-old male infant presenting with a high persistent fever with a fluctuating pattern, pancytopaenia, hepatosplenomegaly, and a high triglyceride level. Initial investigations showed an EBV infection. Considering the persistent signs and symptoms, bone marrow aspiration was performed and confirmed the suspicion of HLH. In addition, the presence of Leishmania infection was shown. The patient was treated with liposomal amphotericin B and had complete resolution of his symptoms. Conclusion: Diagnosis of VL represents a demanding challenge in endemic and non-endemic areas. Our case demonstrates that leishmaniasis should always be considered in the differential diagnosis in patients presenting with hepatosplenomegaly and cytopaenia with a persistent fever, even in cases of infectious mononucleosis. Moreover, the execution of bone marrow aspiration should not be delayed in order to diagnose and treat at an early stage the potential occurrence of VL, especially if complicated with HLH.