Background: Visceral leishmaniasis related-hemophagocytic lymphohistiocytosis (VL-HLH) is a hemophagocytic syndrome caused by Leishmania infection. VL-HLH is rare, especially in nonendemic areas where the disease is severe, and mortality rates are high. The key to diagnosing VL-HLH is to find the pathogen; therefore, the Leishmania must be accurately identified for timely clinical treatment.Case presentationWe retrospectively analyzed the clinical data, laboratory examination results and bone

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... rrow cell morphology of two children with VL-HLH diagnosed via bone marrow cell morphology between July 2017 and January 2021 at Kunming Children's Hospital of Yunnan, China.Two cases suspected of having malignant tumors at other hospitals and who had undergone ineffective long-term treatment were transferred to Kunming Children's Hospital. They had repeated fevers, pancytopenia, hepatosplenomegaly, hypertriglyceridemia, and hypofibrinogenemia over a long period and met the HLH-2004 standard. Their HLH genetic test results were negative, and primary HLH was excluded. Both children underwent chemotherapy as per the HLH-2004 chemotherapy regimen , but it was ineffective and accompanied by serious infections. We found Leishmania amastigotes in their bone marrow via morphological examination of their bone marrow cells, which showed hemophagocytic cells; thus, the children were diagnosed with VL-HLH. After being transferred to a specialty hospital for treatment, the condition was well-controlled. Conclusion: Morphological examination of the bone marrow cells played an important role in diagnosing VL-HLH. When clinically diagnosing secondary HLH, VL-HLH should be considered in addition to common pathogens, especially in patients for whom HLH-2004 chemotherapy regimens are ineffective. For infants and young children, bone marrow cytology examinations should be performed several times and as early as possible to find the pathogens to reduce potential misdiagnoses.