Mutations of the MORC2 gene have most commonly been associated with autosomal-dominant Charcot-Marie-Tooth disease type 2Z (CMT 2Z), while the impact of MORC2 mutations in CMT 2Z on neuronal biology and their phenotypic consequences in patients remain to be clarified. We reported a 27-month-old child with a developmental lag of more than 1 year. He had progressive fatigue for 4 months, accompanied by dysphagia, choking while eating, and progressive aggravation. A genetic study revealed a de novo variant of MORC2, which has not yet been reported. According to the child's clinical manifestations, genetic pattern, and American College of Medical Genetics and Genomics pathogenicity analysis, the patient was diagnosed with CMT 2Z caused by MORC2 gene mutation. Mitochondrial cocktail therapy (arginine, vitamin B1 tablets, vitamin B2 tablets, coenzyme Q10 capsules, L-carnitine oral liquid, idebenone tablets, etc) was given. Mitochondrial cocktail therapy did not significantly improve the child's condition, head magnetic resonance imaging lesions were not significantly improved at outpatient follow-up more than 1 month later, and the lesions were basically unchanged. The clinical manifestations of the disease were similar to those of Leigh syndrome, and they were not significantly improved by cocktail therapy. This site has not been reported in the literature domestically or abroad, and the pathogenesis of CMT 2Z caused by this site mutation is indeed not related to mitochondrial dysfunction. Our study is helpful for clinicians with regard to the differential diagnosis of Leigh syndrome and CMT 2Z and improvement of clinicians' understanding of CMT 2Z disease.

MORC2 encodes an ATPase that plays a role in chromatin remodeling, DNA repair, and transcriptional regulation. Heterozygous variants in MORC2 have been reported in individuals with autosomal-dominant Charcot-Marie-Tooth disease type 2Z and spinal muscular atrophy, and the onset of symptoms ranges from infancy to the second decade of life. Here, we present a cohort of 20 individuals referred for exome sequencing who harbor pathogenic variants in the ATPase module of MORC2. Individuals presented with a similar phenotype consisting of developmental delay, intellectual disability, growth retardation, microcephaly, and variable craniofacial dysmorphism. Weakness, hyporeflexia, and electrophysiologic abnormalities suggestive of neuropathy were frequently observed but were not the predominant feature. Five of 18 individuals for whom brain imaging was available had lesions reminiscent of those observed in Leigh syndrome, and five of six individuals who had dilated eye exams had retinal pigmentary abnormalities. Functional assays revealed that these MORC2 variants result in hyperactivation of epigenetic silencing by the HUSH complex, supporting their pathogenicity. The described set of morphological, growth, developmental, and neurological findings and medical concerns expands the spectrum of genetic disorders resulting from pathogenic variants in MORC2.