Diffuse pulmonary ossification (DPO) is a rare disease characterized by diffuse small bone fragments in the lung tissue. It is usually discovered at autopsy. We describe a case where DPO was detected on lung biopsy for evaluation of Interstital lung disease (ILD).
A 72 yr-old man was admitted for midsternal chest pain and shortness of breath. He reported gradual worsening of dyspnea and cough over a few years. Other medical history included diabetes, Hypertension and chronic renal insufficiency. He was an Ex-smoker with no significant environmental or recreational risk exposure. Physical examination revealed bilateral basilar ronchi. Chest radiograph revealed fine nodular interstitial pattern. A high resolution chest CT revealed extensive peripheral pulmonary fibrosis, “bright” nodularity and interlobular septal thickening (Fig 1). Video assisted thoracoscopic lung biopsy revealed patchy interstitial fibrosis with metaplastic bone formation generally in association with fibrotic foci with a background of pan-acinar emphysema (Fig 2). These findings were consistent with DPO of the “nodular” variety.
Pulmonary ossification is defined by the histologic presence in the lung of mature bone often containing marrow elements. This can be either a primary idiopathic process or secondary to a number of pulmonary, cardiac, orextracardiopulmonary disorders. Diffuse Pulmonary Ossification (DPO), may be either granular or dendriform. The nodular form is characterized by lamellar deposits of calcified osteoid material situated within the alveolar spaces often without marrow elements. Dendriform ossification refers to interstitial branching spicules of bone and marrow elements that may protrude into the alveoli and often follows interstitial fibrosis.Tissue injury is the most important provoking factor. An alkaline environment, initiates precipitation of calcium salts, enables alkaline phosphatase activity, and activates profibrogenic cytokines. Alveolar bleeding is responsible for interstitial metallic deposition that attracts calcium salts and multinucleated giant cells..DPO is most commonly found in men between 70 and 80 years of age, but cases have been reported in young men and women. Many cases are diagnosed at autopsy. The signs, symptoms, and physiological abnormalities pointing to DPO may be secondary to another process. Pulmonary ossification is not usually visible in chest x-rays. When visible, it appears in the inferior lobes as an unspecified reticulonodular density. In most cases it is difficult to determine whether the very fine lines in the x-ray image indicate calcified areas or pulmonary fibrosis. Consequently, the disease is usually discovered by chance during autopsy. High resolution CT scans of the thorax reveal lines of 1 to 4 mm in the form of either branching calcifications of bronchovascular distribution in the dendriform type or multiple areas of tiny calcified subpleural nodules in the nodular type. Establishing a prognosis is difficult as few living cases are diagnosed. Some case reports describe no changes of interest over time; others describe a slow evolution.The literature contains no cases of spontaneous regression.
Diffuse pulmonary ossification is under-recognized and under-reported. Its pathological significance remains unknown. Creation of a registry and continued follow-up of these patients may pave the way for better understanding of pathogenesis and natural course of this disease.
Andres Escobar Naranjo, No Financial Disclosure Information; No Product/Research Disclosure Information