Bone Marrow Eosinophilia Causing Pancytopenia in Pulmonary Tuberculosis: A Curious Case

Eosinophilia, especially tissue eosinophilia is very rare in pulmonary tuberculosis. Here we describe a case of pancytopenia resulting from bone marrow eosinophilia probably triggered by Mycobacterium tuberculosis.A 61- year-old male presented to us with cough and dyspnoea on exertion for the past 6 months with intermittent fever for the last 3 months. He didn't had any comorbidities, atopic disease, any addiction or drug intake. He was treated for pulmonary tuberculosis 22 years ago. He had received two units of blood transfusion in the past 3 months because of persistent pancytopenia. His general and systemic examinations were unremarkable except for pallor and bilateral diffuse rhonchi with crepitation over the chest. Initial blood investigations revealed pancytopenia (Haemoglobin-6.3g/dl, Total leucocyte count-1400cells/ul, Platelet count-60000/ul), mild eosinophilia (Absolute eosinophil count- 580cells/cumm), with blood peripheral smear showing normocytic normochromic picture with mild eosinophilia and no haemoparasite. Erythrocyte sedimentation rate was 115mm at 1-hour. Rapid filarial antigen was not detected. Stool for ova, cyst was normal. Liver function and renal function tests were normal. CECT Chest showed peribronchial thickening of central bronchi with fibrotic nodule and band in the apical segment of right upper lobe causing traction bronchiectasis, and non-necrotic mediastinal lymphadenopathy. Sputum culture was sterile with acid-fast stain and cartridge-based nucleic acid amplification test (CBNAAT) for Mycobacterium tuberculosis were negative. He was managed with antibiotics, albendazole, diethylcarbamazine but showed no improvement. On further workup for persistent symptoms, pancytopenia and mild eosinophilia, serum total IgE was found markedly elevated (2701 IU/ml). HIV I & II, ANA, P-ANCA, C-ANCA were negative, with normal angiotensin-converting enzyme (20 U/L) and aspergillus fumigatus-specific IgE (0.06 kUA/L). Bone marrow aspiration and biopsy showed a cellular marrow with trilineage haematopoiesis with 49% eosinophils and its precursor, without any cellular atypia. Bronchoalveolar lavage revealed positive CBNAAT test for Mycobacterium tuberculosis and a sterile culture for bacteria and fungi. He was discharged with antitubercular therapy, short course steroid, and lost to follow up during the COVID-19 pandemic.Though both peripheral and tissue eosinophilia are rare in tubercular infection with very few reported cases, our patient had significant bone marrow eosinophilia with markedly increased serum IgE level. So peripheral and bone marrow eosinophilia may be due to hypersensitivity reaction to Mycobacterium antigen in a susceptible patients. IL-5 has been implicated as an important cytokine for the expansion of peripheral/tissue eosinophilia in tuberculosis patients. So it needs further research to ascertain the cause or association hypothesis.