Case Report: Diagnosis and Treatment of Two Clinical Cases of Visceral Leishmaniasis-Related Hemophagocytic Lymphohistiocytosis.

Visceral leishmaniasis-related hemophagocytic lymphohistiocytosis (VL-HLH) is a potentially life-threatening secondary hemophagocytic lymphocytic syndrome caused by protozoan parasites of the Leishmania species and transmitted by infected sandflies. Therefore, it is important to be highly vigilant of the infection, particularly the visceral subtype, to share information with the public health system, and to improve the early diagnosis rate so that appropriate treatment can be initiated promptly. We report two isolated cases of VL-HLH. The main clinical manifestations were fever, pancytopenia, splenomegaly, hypofibrinogenemia, and hyperferremia, which meet the HLH-2004 diagnostic criteria. In our experience, anti-HLH treatment was not very effective for either case. No Leishmania organism was found in the first bone marrow smear of either patient. The first patient was diagnosed after identification of Leishmania amastigotes via sternal bone marrow biopsy, rK39 immunochromatography test, and metagenomic next-generation sequencing. The other patient was diagnosed by rK39-rapid diagnostic test and polymerase chain reaction. However, because of the delayed diagnosis in both cases, their conditions continued to deteriorate and both patients eventually died of the disease. Leishmaniasis is a parasitic disease with regional specificity and a low incidence. The occurrence of secondary HLH has a great impact on prognosis. When encountering secondary HLH in clinical practice, leishmaniasis should remain on the list of differential causes. Because of a high mortality rate if diagnosed late, it is crucial to be vigilant of VL-HLH in practice so that early detection, diagnosis, and treatment of the disease can be achieved to reduce adverse patient outcomes.