Idiopathic diffuse pulmonary ossification with multiple misdiagnoses of pulmonary tuberculosis: a case report

Diffuse pulmonary ossification (DPO) is a rare interstitial lung disease characterized by ectopic bone formation within the lung parenchyma. Due to its nonspecific clinical and radiological features, DPO is frequently misdiagnosed as pulmonary tuberculosis or other chronic pulmonary infections, particularly in tuberculosis-endemic regions. We report a 34-year-old man presenting with intermittent hemoptysis for six months. Chest computed tomography revealed multiple punctate, nodular, and linear high-density lesions with partial calcification, predominantly in the lower lobes and subpleural regions of both lungs. The patient had been repeatedly misdiagnosed with pulmonary tuberculosis at several institutions, despite negative microbiological and bronchoscopic evaluations. Bone scintigraphy demonstrated scattered abnormal pulmonary uptake with mildly increased bone metabolism. Whole-exome sequencing identified a mutation in the MUC5B gene, while no mutation in SLC34A2 was detected. Video-assisted thoracoscopic lung biopsy revealed scattered mature bone and bone marrow tissue within the lung parenchyma, confirming the diagnosis of diffuse pulmonary ossification. After exclusion of secondary causes, idiopathic DPO was diagnosed. No specific treatment was administered, and the patient remained clinically stable during follow-up. This case highlights that DPO should be considered in patients with diffuse pulmonary calcifications and negative microbiological evidence of infection, particularly in tuberculosis-endemic settings. Bone scintigraphy and surgical lung biopsy may provide important diagnostic value. Notably, the identification of a MUC5B variant suggests a potential link between DPO and fibrotic lung disease, warranting further investigation.