Idiopathic Dendriform Pulmonary Ossification Diagnosed by Transbronchial Lung Cryobiopsy: A Case Report

Dendriform pulmonary ossification (DPO) is a rare condition characterized by ossification in the lungs. Lung ossification can be categorized into idiopathic ossification or secondary ossification associated with underlying pulmonary, cardiac, and systemic disorders. We herein present a case of a 60-year-old man with bilateral reticulonodular shadows detected on chest radiography during a medical checkup. A transbronchial lung biopsy did not provide a definitive diagnosis, and the asymptomatic patient was referred to our hospital due to worsening imaging findings. Further evaluation, including transbronchial lung cryobiopsy (TBLC), revealed dendriform ossification with components of bone marrow within the lung parenchyma. In the absence of underlying disease, the patient was diagnosed with idiopathic DPO (IDPO). This case highlights the importance of considering DPO in the differential diagnosis of unexplained pulmonary ossification and suggests that TBLC is a useful diagnostic tool for IDPO.