IntroductionPulmonary alveolar microlithiasis (PAM) is an uncommon, autosomal recessive lung disease with high penetrance (OMIM #265 100) and is considered to be a monogenic disorder. 1 The only known pathogenic gene is solute carrier family 34 member 2 (SLC34A2) (Entrez Gene ID 10568).2-4 SLC34A2 mutations lead to the accumulation of calcium phosphate in the alveoli, restrict alveolar dilatation, and then progress to a restrictive lung function complicated with reduced dynamic and static volumes.5, 6 Dyspnea is the most frequent symptom, followed by dry cough, chest pain, asthenia, pneumothorax, pulmonary fibrosis, and cor pulmonale.7-10While children are always in the onset at the early stage of PAM and usually remain asymptomatic when diagnosed; however, some can present with dry cough, exertional dyspnea, and chronic hypoxic signs, including clubbing.3 Recently, some complications with PAM have been reported, such as asthma, pneumomediastinum, subcutaneous emphysema, and so on.11-14PAM is difficult to be diagnosed because of nonspecific symptoms in children. The diagnosis of PAM is often based on radiographic studies at first, and an exact diagnosis requires at least one additional clinical feature including genetic testing demonstrating a mutation in SLC34A2, microlith analysis, or histopathology.15 Gradually, it has been a tendency that gene analysis would play an increasingly important role in the diagnostic procedure. Bendstrup et al. summarized 30 genetic variants of SLC34A2 in 2020.16In this case, we identified a PAM patient complicated with bronchitis obliterans by computerized tomography (CT), bronchoscopy and whole-exome-sequencing. Two novel compound heterozygous gene mutations, gain (EXON:2-6 duplication) and c.1218C>A (p. Phe406Leu) were identified to expand the spectrum of gene mutations.