Pulmonary alveolar microlithiasis (PAM) is a rare autosomal recessive disorder characterized by the deposition of calcium phosphate microliths throughout the lungs. Currently the mutation of SLC34A2 gene was considered responsible for PAM. Here we reported the studies on mutation analysis of the SLC34A2 gene in three familial members and one unrelated subject of PAM by DNA direct sequencing. Meanwhile, we also reviewed and analyzed the published studies of the SLC34A2 gene mutation in PAM patients. The three familial patients were siblings of an inbred family whose parents were cousins. All four patients presented recurrent cough and exertional dyspnea. Diagnosis of PAM was made according to the typical manifestation of radiology. One homozygous mutation of the SLC34A2 gene, c.910A > T (p.K304X) was identified. The review of the SLC34A2 gene mutation showed multiple mutation symbols in PAM patients from China, Turkey, and Japan respectively. The present study supports that the clinical features, pathological and radiological characteristics of Chinese PAM patients are similar to those reported in other countries. Our investigation revealed that the c.910A > T mutation in the SCL34A2 gene was responsible for PAM patients in China. The review of literatures suggests that exon7 and exon8 seemed liable to be affected typical Mongoloid of PAM, and exon8 might be the screen target for Chinese patients.

Phenylalanine hydroxylase deficiency (PAHD), one of the genetic disorders resulting in hyperphenylalaninemia, has a complex phenotype with many variants and genotypes among different populations. Here, we describe the mutational and phenotypic spectrum of PAHD in a cohort of 420 patients from neonatal screening between 1999 and 2016. The observed phenotypes comprised 43.57% classic phenylketonuria, 33.10% mild PKU, and 23.33% mild hyperphenylalaninemia, with an overall PAHD incidence of 1 in 20,445. Genetic testing was performed for 209 patients and 72 variants including seven novel variants were identified. These included two synonymous and five pathogenic nonsynonymous variants (p.S36*, p.T186I, p.L255W, p.F302V and p.R413H). The most common variant among all patients was p.R243Q, followed by p.R241C, p.Y204C, p.R111* and c.442-1G > A. Variants p.R53H and p.F392I occurred only in MHP with 19.3% and 8.0% of the observed alleles respectively. The genotypes p.[R241C];[R243Q], p.[R243Q];[R243Q], and p.[Y204C];[R243Q] were abundant across all PAHD patients. The distributions of the null allele and the three defined genotypes, null/null, null/missense, and missense/missense, were significantly different between the cPKU and mPKU patients. However, no significant differences were found between mPKU and MHP patients, indicating that other modifier factors influence the phenotypic outcome in these patients. The data presented here will provide a valuable tool for improved genetic counseling and management of future cases of PAHD in China.

Background Newborn screening (NBS) has been implemented for neonatal inborn disorders using various technology platforms, but false-positive and false-negative results are still common. In addition, target diseases of NBS are limited by suitable biomarkers. Here we sought to assess the feasibility of further improving the screening using next-generation sequencing technology. Methods We designed a newborn genetic sequencing (NBGS) panel based on multiplex PCR and next generation sequencing to analyze 134 genes of 74 inborn disorders, that were validated in 287 samples with previously known mutations. A retrospective cohort of 4986 newborns was analyzed and compared with the biochemical results to evaluate the performance of this panel. Results The accuracy of the panel was 99.65% with all samples, and 154 mutations from 287 samples were 100% detected. In 4986 newborns, a total of 113 newborns were detected with biallelic or hemizygous mutations, of which 36 newborns were positive for the same disorder by both NBGS and conventional NBS (C-NBS) and 77 individuals were NBGS positive/C-NBS negative. Importantly, 4 of the 77 newborns were diagnosed currently including 1 newborn with methylmalonic acidemia, 1 newborn with primary systemic carnitine deficiency and 2 newborns with Wilson’s disease. A total of 1326 newborns were found to be carriers with an overall carrier rate of 26.6%. Conclusion Analysis based on next generation sequencing could effectively identify neonates affected with more congenital disorders. Combined with C-NBS, this approach may improve the early and accurate identification of neonates with inborn disorders. Our study lays the foundation for prospective studies and for implementing NGS-based analysis in NBS.

We recently diagnosed a patient with pulmonary alveolar microlithiasis (PAM). Because loss-of-function mutations of the SLC34A2 gene are responsible for the development of PAM, we sought to sequence the SLC34A2 gene of the patient and his direct relatives, with a purpose to identify mutations that caused the PAM of the patient as well as the carriers of his family. We found a novel compound heterozygous mutation of the SLC34A2 gene in this patient, which were the mutations of c.1363T > C (p. Y455H) in exon 12 and c.910A > T (p. K304X) in exon 8. Computational prediction of three-dimensional (3D) structures of the mutants revealed that the Y455H mutation resulted in a formation of irregular coils in the trans-membrane domain and the K304X mutation resulted in protein truncation. Our study suggested that sequencing of the SLC34A2 gene together with a computational prediction of the 3D structures of the mutated proteins may be useful in PAM diagnosis and prognosis.

The NOTCH3 mutation spectrum in our group was diverse and consistent with those in Caucasians but differed from those in Korea and Taiwan. The screening strategy used in Caucasian populations can be applied to mainland Chinese patients. Atherosclerosis of the large intracranial arteries involvement does not exclude CADASIL diagnosis.