LAUSR

Introduction: Pulmonary alveolar microlithiasis (PAM) is an infrequent autosomal recessive lung disease, caused by a homozygous mutation in the SLC34A2 gene, which encodes a type IIb sodium-dependent phosphate cotransporter expressed in lungs and small intestine. The altered function of this cotransporter causes the intra-alveolar accumulation of phosphate leading to the formation of microliths. Case report: A 27-year-old Moroccan female was studied because of lumbar pain one year after pregnancy. The lumbar spine x-ray showed interstitial pattern in lung bases. Pulmonary evaluation was then requested with a chest CT scan. She was visited at the ILD-Unit admitting a history of progressive dyspnea on exertion and dry cough for 5 years, and co-sanguinity between her parents (first cousins). The physical examination revealed basal bilateral dry crackles, 98% oxygen saturation at rest and clubbing. Pulmonary function tests showed a mild restrictive pattern with moderate alteration of DLCO, and a desaturation of 6% at the 6MWT when walking 415 meters. Blood analysis showed negative autoimmunity and an increase in parathyroid hormone with a decrease in calcidiol levels and low fractional urinary calcium excretion which improved with vitamin D replacement therapy. Thorax HRCT revealed widespread micro‑calcifications, ground‑glass opacities, interlobular septal thickening and subpleural cysts. Microliths were identified in the BAL sample. Genetic study was performed and the pathogenic variant c.1328delT (p.Leu443Argfs*6) was detected in the SLC34A2 gene. Conclusions: Calcium metabolism disorder is concomitant to PAM in this patient and is not associated to the altered SLC34A2 gene.