INTRODUCTION:We report a case of dendriform pulmonary ossification (DPO) with clinical follow-up over 14 years. This is a rare disorder of unknown cause which is most commonly diagnosed as an incidental finding at autopsy.
CASE PRESENTATION:An Ethiopian-born male presented in 1993 at age 43 years with dyspnea and diffuse interstitial infiltrates. He is atopic with allergic rhinitis and asthma. He has never smoked. He has insulin-dependent diabetes and CAHD. Only medications were aspirin and insulin. He has always worked in white collar jobs. Physical examination was unremarkable. PFTs revealed mild restriction, DLCO of 23.7 ml/min/mmHg and no airflow obstruction (AWO). Normal WBC. Negative collagen vascular screen. ACE WNL. PPD negative. He did not follow-up for two years, before re-presenting complaining of worsening DOE. Repeat PFTs then documented mild AWO and a decline in TLC and DLCO. Chest CT revealed mild diffuse ILD with scattered punctate calcifications. A gallium scan showed no parenchymal uptake of tracer. He underwent open lung biopsy in July 1995; tissue revealed isolated fragments of trabecular bone containing marrow elements within the interstitium. Adjacent lung was characterized by mild interstitial fibrosis with chronic inflammation. These findings were consistent with DPO. Because of the inflammation, glucocorticoid therapy was suggested to the patient, who refused, due to concern about his diabetes.There has been interval follow-up since 1995 with evidence for very slow progression of parenchymal lung disease with appearance of more abundant punctate calcifications. The lung volumes and DLCO have declined slightly over 14 years. Symptomatically, he is more DOE, but has gained 25 pounds and is more sedentary.
DISCUSSIONS:Pulmonary ossification is a rare condition, defined by the finding of mature bone in the lung, often containing marrow elements. A recent review of lung bone formation (1) classifies the disorder as either primary idiopathic (IPO) or secondary to a number of pulmonary, cardiac and other disorders. Among the associated pulmonary diseases are IPF, ARDS, sarcoidosis, histoplasmosis, tuberculosis and metastases from osteogenic sarcoma or melanoma. Our patient clearly does not have any of these conditions except possibly histoplasma exposure. Associated cardiac disorders are chronic LVF, mitral stenosis and IHSS, none of which he evidences. Our patient likely has IPO. The pathogenesis of this rare condition is unknown. Interstitial deposition of bone can be either localized or diffuse, and either nodular or dendriform. DPO refers to branching spicules of bone in the interstitium that may protrude into alveolar spaces. Most cases are diagnosed at autopsy. Published case reports describe restrictive physiology with low DLCO when disease is extensive. Ours is the first report of long-term follow-up of the disease identified in a middle-aged man, in whom slow progression of ossification has been observed.
CONCLUSION:IPO is a rare condition that may be associated with some lung and heart diseases. The clinical course is unknown, but our case suggests that the condition may slowly progress over time with more extensive deposition of bone in lung parenchyma.
DISCLOSURE:Jalil Ahari, No Product/Research Disclosure Information; No Financial Disclosure Information