Background: Propionic acidemia (PA)(OMIM#606054) is an inborn error of branched-chain amino acid metabolism, caused by defects in the propionyl-CoA carboxylase (PCC) enzyme which encoded by the PCCA and PCCB genes.
Case presentation: Here we report a Chinese neonate diagnosed with suspected PA based on the clinical symptoms, gas chromatography-mass spectrometry (GC/MS), and brain imaging tests. Targeted next-generation sequencing (NGS) was performed on the proband. We detected only one heterozygous recurrent nonsense variant (c.937C > T, p.Arg313Ter) in the PCCA gene. When we manually checked the binary alignment map (BAM) diagram of PCCA gene, we found a heterozygous deletion chr13:100915039-100915132delinsAA (c.773_819 + 47delinsAA) (GRCh37.p13) inside the exon 10 in the PCCA gene. The results were validated by Sanger sequencing and qPCR method in the family: the variant (c.937C > T, p.Arg313Ter) was in the maternal allele, and the delins was in the paternal allele. When the mother was pregnant again, prenatal diagnosis was carried out through amniocentesis at 18 weeks gestation, the fetus carried neither of the two mutations. After birth, newborn screening was undertaken, the result was negative.
Conclusions: We identified a recurrent c.937C > T and a novel c.773_819 + 47delinsAA mutations in the PCCA gene, which may be the genetic cause of the phenotype of this patient. Our findings expanded the spectrum of causative genotype-phenotype of the PCCA gene. For the cases, the NGS results revealed only a heterozygous mutation in autosomal recessive disease when the gene is associated with phenotypes, it is necessary to manually check the BAM diagram to improve the detection rate. Targeted NGS is an effective technique to detect the various genetic lesions responsible for the PA in one step. Genetic testing is essential for genetic counselling and prenatal diagnosis in the family to avoid birth defects.
Keywords: BAM diagram; Delins; PCCA; Propionic acidemia; Propionyl-CoA carboxylase; Targeted NGS.