Pulmonary alveolar microlithiasis. A clinicopathologic and chemical analysis of seven cases

To determine the clinical features and outcome of patients with pulmonary alveolar microlithiasis and to determine the chemical composition of the microliths.

We studied seven cases of pulmonary alveolar microlithiasis. The patients were six women and one man, aged 19 to 70 years (mean age 44.5 years). Clinically, five patients were known to have suffered from this condition for 5 to 41 years. One patient presented with shortness of breath, and another had a gradual decrease in exercise tolerance. None of the patients had a previous history of disturbances in metabolism or any other relevant medical condition. Reports on radiographic studies were available in six cases, and chest radiographs were available for review in the seventh case. They all showed diffuse bilateral pulmonary infiltrates. Open lung biopsies were performed in two patients, and autopsy lung material was reviewed in five patients.

Histologically, the lung showed the typical features of pulmonary alveolar microlithiasis, that is, presence of numerous microliths filling the alveolar spaces with either a normal or thickened fibrotic interstitium. Chemical analysis performed on the lung tissue of six of these patients revealed that the microliths consisted principally of calcium and phosphorus salts. Five of these patients died of respiratory failure; however, their deaths occurred from 5 to 41 years following the initial diagnosis. No follow-up information was obtained in two patients.

The findings of this study confirm that pulmonary alveolar microlithiasis can be seen in any age group and that the microliths are composed principally of salts of calcium and phosphorus. Additionally, these cases confirm that the disease typically follows a protracted course.