Dendriform Pulmonary Ossification in the Absence of Usual Interstitial Pneumonia: CT Features and Possible Association With Recurrent Acid Aspiration.

OBJECTIVE: Dendriform pulmonary ossification (DPO) is a rare lung disease in which mature bone is present in the peripheral interstitium of the lung. It typically occurs in patients with usual interstitial pneumonia (UIP). We assessed patients with CT findings of DPO without UIP to determine possible causative factors and to assess the clinical and CT course. We hypothesized that DPO without UIP would be a unique entity.

MATERIALS AND METHODS: We retrospectively reviewed CT reports for the word "ossification." Two observers reviewed each examination for micronodules 1-5 mm in diameter in the peripheral interstitium (subpleural and perifissural spaces and interlobular septa), some of which had high attenuation on mediastinal windows, presence of contiguous clusters of nodules resulting in a branching pattern, and lack of findings of UIP or focal lung disease. We reviewed the electronic medical records and follow-up CT and clinical information in all eligible patients.

RESULTS: The study population consisted of 52 men with a median age of 79 years old. Seventy-five percent of the patients had gastroesophageal reflux disease, obstructive sleep apnea, or a chronic neurologic disorder. No progressive pulmonary symptoms were attributed directly to DPO, and no patient developed pulmonary fibrosis or suffered clinical decline from DPO. CT showed minimal progression or remained stable at follow-up (77% for at least 1 year, 25% for over 4 years).

CONCLUSION: DPO in the absence of UIP occurs in elderly men and appears to be associated with chronic aspiration of gastric acid. The course is indolent.