Pulmonary alveolar microlithiasis (PAM) is a rare disease that affects both lungs. It is characterized by the presence of small calculi (calcium phosphate) within the alveolar spaces. We report the case of a 26-year-old female whose diagnosis was based on characteristic findings on chest X-rays and high-resolution computed tomography scans. The patient, 28 weeks pregnant, was rehospitalized 10 months after the diagnosis, presenting hypoxemic acute respiratory failure and severe restrictive ventilatory defect on spirometry. After 32 completed weeks of gestation (228 days), she was submitted to cesarean section, and the outcome was successful for mother and newborn. PAM has a variable clinical course. It is suggestive of an autosomal recessive inheritance pattern and has been associated with positive family history. The etiology of PAM is unclear, and many authors speculate that there is a local enzymatic defect responsible for the intra-alveolar accumulation of calcium. Reports of patients with PAM who become pregnant are exceptional, and this is the first case described in Brazil. The course of this disease is usually slow and progressive, and patients typically die of cardiorespiratory failure. The present case illustrates the need to offer female patients, especially those with advanced disease, genetic counseling and orientation regarding the risks of pregnancy. Currently, the only effective therapy is lung transplantation.

Keywords: Pulmonary alveoli; Pregnancy; Respiratory insufficiency.