Adult Primary Hemophagocytic Lymphohistiocytosis (HLH) Initially Suspected as Brucellosis-Associated HLH: A Case Report

Hemophagocytic lymphohistiocytosis (HLH) is a rare hyperinflammatory syndrome. Due to overlapping symptoms, primary HLH can be challenging to distinguish from brucellosis-associated HLH. This report describes the case of a 40-year-old male farmer who presented with progressive pancytopenia, body aches, fatigue, anorexia, weight loss, and fever. Laboratory examination showed severe leukopenia, anemia, thrombocytopenia, and abnormal liver function tests. Serology was positive for Brucella, but bone marrow culture was negative. Bone marrow biopsy showed histiocytic hemophagocytosis and preserved megakaryocytes. This confirmed HLH. Autoimmune and septic workup were unremarkable. Initially, the patient was suspected of having brucellosis-associated HLH, and anti-Brucella therapy was started, but cytopenia persisted. HLH-directed therapy was initiated. Treatment with dexamethasone and intravenous immunoglobulin resulted in hematological and clinical improvement. After thorough exclusion of infections and autoimmune disorders, a working diagnosis of primary HLH was established. The patient was discharged on oral corticosteroids with continuation of anti-Brucella therapy and scheduled chemotherapy. The patient showed continuous improvement after three cycles. This case shows the diagnostic complexity of HLH mimicking infection-associated syndromes.