Background Brucellosis can mimic various multisytem diseases,showing wide clinical polymorphism that frequently leads to misdiagnosis and treatment delay,further increasing the complication rates.In this study,we aimed to examine bone marrow biopsy findings in brucellosis cases presenting with hematologic abnormalities.Methods Forty-eight brucellosis cases were prospectively investigated.Complaints and physical examination findings of patients were recorded.Patients' complete blood count,routine biochemical tests,erythrocyte sedimentation rate,C-reactive protein and serological screenings were performed.Bone marrow biopsy and aspiration was performed in patients with cytopenia,for bone marrow examination and brucella culture,in accordance with the standard procedures from spina iliaca posterior superior region of pelvic bone.Results Of the 48 patients,35 (73％) were female and 13 (27％) were male.Mean age was (34.8±15.4) years (age range:15-70 years).Anemia,leukopenia,thrombocytopenia and pancytopenia were found in 39 (81％),28 (58％),22 (46％) and 10 patients (21％),respectively.In the examination of bone marrow,hypercellularity was found In 35 (73％) patients.Increased megacariocytic,erythroid and granulocytic series were found in 28 (58％),15 (31％) and 5 (10％) patients,respectively.In addition,hemophagocytosis was observed in 15 (31％) patients,granuloma observed in 12 (25％) and increased eosinophil and plasma cells observed in 9 (19％) patients.Conclusion According to the results of our series,hemophagocytosis,microgranuloma formation and hypersplenism may be responsible for hematologic complications of brucellosis.