Phenotypes and pathogenic variations in two cases of propionic acidemia / 中华围产医学杂志

ABSTRACT

Objective:To investigate the clinical characteristics and pathogenic mutations of propionic acidemia.Methods:Clinical data of two patients with propionic acidemia admitted to the Obstetrics and Gynecology Hospital of Nanjing Medical University from May 2017 to June 2018 were collected. Genomic DNA was extracted from the peripheral blood of the patients and their parents. Inherited disease panel based on Ion Torrent semiconductor sequencing technology was performed to detect gene mutations, and those with suspected pathogenic mutations were verified by Sanger sequencing. Descriptive statistical analysis was used for data analysis.Results:Case 1 was suspected of sepsis and admitted to the Obstetrics and Gynecology Hospital of Nanjing Medical University due to "drowsiness and milk rejection" on the second day after birth. Tandem mass spectrometry suggested the level of propionyl carnitine and its ratios to acetylcarnitine and free carnitine were increased. Urine gas chromatography-mass spectrometry showed elevated 3-hydroxypropionic acid and methylcitric acid. Genetic analysis revealed that the infant carried c.331C>T (p.R111X)/c.1228C>T (p.R410W) compound heterozygous mutations in the PCCB gene. The infant was diagnosed with propionic acidemia and treated with a special diet with an L-Carnitine supplement but died of sudden coma and vomiting without precipitating factors at three months of age. Case 2 presented with sudden vomiting, drowsiness, and anergia on the admission at five-months old. Tandem mass spectrometry showed increased propionyl carnitine level and its ratios. Compound heterozygous mutations of c.146delG (p.G49EfsX16)/c.1253C>T (p.A418V) in the PCCB gene were identified in the patient, of which c.146delG (p.G49EfsX16) was a de novo mutation and was evaluated as a pathogenic mutation. The patient was on a special diet with an L-Carnitine supplement, but with disobedience. Followed up to the age of three years and eight months, the child was severely underdeveloped. Conclusions:Neonates with clinically suspected sepsis may have propionic acidemia, and tandem mass spectrometry and genetic testing should be performed as soon as possible to confirm or rule out the diagnosis. Further investigations on the pathogenesis and function of the new mutation are still needed.