Pulmonary alveolar microlithiasis. A case report with a discussion of differential diagnosis.

The rare disease of pulmonary alveolar microlithiasis is characterized by innumerable microscopic stones, mainly of tribasic calcium phosphate, within the pulmonary alveoli. In a 13-year-old boy an earlier radiological examination showed diffuse lung opacity. The main differential diagnoses taken into consideration were sarcoidosis, idiopathic hemosiderosis, diffuse interstitial fibrosis and alveolar proteinosis. The correct diagnosis was made after a lung biopsy which showed intra-alveolar microliths. The radiological findings are in agreement with the reports in the literature. The specific X-ray features of pulmonary alveolar microlithiasis are calcified opacities, nodules, hilifugal trabeculations and pleural striae. These radiological signs are sufficiently diagnostic to restrict lung biopsy to particularly difficult cases. The disease is resistant to all therapeutic measures.