Clinical and molecular genetic analysis of a case of MEGDEL syndrome

Objective To explore the clinical and genetic characteristics of a child with MEGDEL syndrome. Methods Clinical data of the child was reviewed. Peripheral blood samples of the child and his parents were collected. Mitochondrial genome and the whole exome of the child were analyzed by next-generation sequencing. Candidate variants and its origin were verified by Sanger sequencing and fluorescence quantitative PCR. Results The patient, a 2-year-and-6-month-old male, has featured hypoglycemia, mental and motor retardation with regression. Cranial MRI showed bilateral putamen damage suggestive of Leigh syndrome. Testing of urine organic acid indicated that the level of 3-methylpentenoic acid was slightly increased. Whole exome sequencing revealed that the child has harbored heterozygous deletion of exons 6 to 17 and c.307A>T nonsense variant of the SERAC1 gene, which were respectively inherited from his parents who were asymptomatic. Treatment with Levocarnitine, vitamin B1, vitamin B2, coenzyme Q10, baclofen and glucuronolactone resulted in improvement of sleep and mental state. Conclusion A case of MEGDEL syndrome without deafness was diagnosed. Discovery of the nonsense mutation and large fragment deletion have enriched the spectrum of SERAC1 gene variants.