Clinical Implications and Outcomes of Bone Marrow Granulomas

Background: Bone marrow granuloma is an uncommon finding that is associated with diverse underlying etiologies. Its clinical significance and impact on patient prognosis remain poorly understood. Methods We reviewed bone marrow biopsies from a tertiary medical center in Taiwan between 2005 and 2020. Cases with bone marrow granuloma were included and analyzed retrospectively. Results A total of 81 cases were evaluated. The primary cause of bone marrow granuloma was mycobacterial infection (38.3%), followed by hematologic malignancies (25.9%). The diagnosis of mycobacterial infection in these patients was often delayed due to low positivity rates of mycobacteria cultures (9.5%), acid-fast bacilli smears (13.3%), and nucleic acid amplification tests (6.3%) from bone marrow aspirates. We identified splenomegaly, severe hypoalbuminemia, and high C-reactive protein levels as potential diagnostic indicators for mycobacterial infections in patients with bone marrow granulomas. The one-year and two-year mortality rates for patients with bone marrow granuloma were 24.7% and 29.6%, respectively. Male gender (HR, 5.70; p = 0.021), age ≥ 65 years (HR, 3.83; p = 0.008), and pre-existing malignancy (HR, 2.72; p = 0.038) were identified as independent risk factors for 1-year mortality. Interestingly, the underlying cause of bone marrow granulomas did not affect the prognosis. Conclusion Bone marrow granuloma is often a diagnostic challenge and requires extensive investigation, mainly to identify mycobacterial infection. The presence of bone marrow granuloma is associated with poor prognosis, especially in male and elderly patients. Our study highlights the diagnostic and prognostic importance of bone marrow granulomas in clinical practice.