A Pedigree with Pulmonary Alveolar Microlithiasis: A Clinical Case Report and Literature Review

Pulmonary alveolar microlithiasis (PAM) is a rare autosomal recessive disease characterized by the presence of innumerable calcium phosphate microliths in the alveoli. Clinical-radiological dissociation is an important hallmark of this disease. Most PAM patients are asymptomatic and pulmonary tissue changes are discovered incidentally. PAM is pathologically attributable to the formation and aggregation of calcium phosphate microliths in the alveoli after mutations in the SLC34A2 gene (the type IIb sodium-phosphate cotransporter gene) coding NaPi-IIb. In the clinical work, we discovered an inbred pedigree with PAM, which include four PAM siblings. We performed a sequence analysis of the SLC34A2 gene in all members of this PAM pedigree and found that a homozygous mutation c.575C > A (p.T192 K) in exon 6 was involved. To the best of our knowledge, this study was the first to discover nucleotide mutations in exon 6 in Asians.