COQ4 mutations have recently been shown to cause a broad spectrum of mitochondrial disorders in association with CoQ10 deficiency. Herein, we report the clinical phenotype, in silico and biochemical analyses, and intervention for a novel c.370 G > A (p.G124S) COQ4 mutation in a Chinese family. This mutation is exclusively present in the East Asian population (allele frequency of~0.001). The homozygous mutation caused CoQ10 deficiency-associated Leigh syndrome with an onset at 1-2 months of age, presenting as respiratory distress, lactic acidosis, dystonia, seizures, failure to thrive, and detectable lesions in the midbrain and basal ganglia. No renal impairment was involved. The levels of CoQ10 and mitochondrial respiratory chain complex (C) II + III activity were clearly lower in cultured fibroblasts derived from the patient than in those from unaffected carriers; the decreased CII + III activity could be increased by CoQ10 treatment. Follow-up studies suggested that our patient benefitted from the oral supplementation of CoQ10, which allowed her to maintain a relatively stable health status. Based on the genetic testing, preimplantation and prenatal diagnoses were performed, confirming that the next offspring of this family was unaffected. Our cases expand the phenotypic spectrum of COQ4 mutations and the genotypic spectrum of Leigh syndrome.
Background
Wolf-Hirschhorn syndrome (WHS) is a contiguous gene syndrome caused by partial 4p deletion highly variable in size in individual patients. The core WHS phenotype is defined by the association of growth delay, typical facial characteristics, intellectual disability and seizures. The WHS critical region (WHSCR) has been narrowed down and
NSD2
falls within this 200 kb region. Only four patients with
NSD2
variants have been documented with phenotypic features in detail.
Case presentation
Herein, we report the case of a 12-year-old boy with developmental delay. He had dysmorphic facial features including wide-spaced eyes, prominent nasal bridge continuing to forehead, abnormal teething and micrognathia. He also had mild clinodactyly of both hands. Using whole-exome sequencing, we identified a pathogenic mutation in
NSD2
[c.4029_4030insAA, p.Glu1344Lysfs*49] isolated from peripheral blood DNA. Sanger confirmation of this variant revealed it as a de novo truncating variant in the family.
Conclusion
Here, we reported a boy with de novo truncating variant in
NSD2
with atypical clinical features comparing with 4p16.3 deletion related WHS. Our finding further supported the pathogenesis of truncating variants in
NSD2
and delineated the possible symptom spectrum caused by these variants.
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