Haemophagocytic lymphohistiocytosis: case series. Serum ferritin level as an indicator of treatment effectiveness

Introduction: Haemophagocytic lymphohistiocytosis (HLH) is a medical condition associated with the over-activation of the immune system. HLH results from the inactivity of natural killer cells and uncontrolled activity of cytotoxic T lymphocytes and macrophages, with a massive cytokine response. Cytohistological examinations might show haemophagocytes in different tissues (e.g., bone marrow). Among laboratory findings especially(particularly) high ferritin level is often seen. Due to the aggressive course of the disease mortality rate is extremely high. Case reports: The study presented three patients with an acquired form of HLH treated successfully in the Haemato-Oncology Department Medical University of Lublin from September 2018 to April 2021. In case 1 HLH developed during pregnancy. Patient 2 was first hospitalized in the Intensive Care Unit and 10 therapeutic plasma exchanges were carried out. In both patients, stabilization of ferritin levels and remission of the disease were achieved soon after the application of treatment according to the HLH-2004 protocol. Case 3 presents a patient in whom HLH was induced by Epstein-Bárr virus and severe acute respiratory syndrome coronavirus type SARS-CoV-2 infections. In the first stage of treatment, the patient received drugs according to the HLH-2004 protocol, but the serum ferritin did not normalize. The reinfection with (SARS-CoV-2) virus occurred again during the treatment. Due to the disease resistance and the inability to continue the HLH-2004 protocol, it was decided to start ruxolitinib therapy, which resulted in the stabilization of the serum ferritin and improvement of the general condition. The patient was qualified for allogeneic bone marrow transplantation. Conclusions: HLH is a difficult and interdisciplinary diagnostic and treatment problem. It is necessary to popularize knowledge about fast and targeted diagnostics. Among laboratory finding the ferritin concentration seemed to be especially helpful as a predictor of treatment effectiveness. Proper diagnosis and treatment introduced as early as possible could save patients’ life.