ABSTRACT
Objective:To analyze the clinical characteristics of a case of CNNM2 gene heterozygous mutation causing hypomagnesemia epilepsy mental retardation (HOMGSMR1) [MIM: 616418] in a child, and explore the association between genotype and phenotype.Methods:We followed up and retrospectively analyzed the clinical characteristics of a case of HOMGSMR1 caused by CNNM2 gene heterozygous mutation treated at Maternal and Child Health Care Hospital of Liuyang. Through whole exome sequencing of the family and bioinformatics analysis of the original data, we consulted databases and literature materials such as Online Mendelian Inheritance in Man (OMIM), ClinVar, gnomAD, GeneReviews, Pubmed, and China National Knowledge Infrastructure (CNKI), The American College of Medical Genetics and Genomics (ACMG) guidelines were used to rate heterozygous deletion mutations in the locked CNNM2 gene.Results:Patient, male, 3 months and 18 days old, mother gave birth to 1 child with 1 pregnancy, recurrent convulsions for more than 10 days, and multiple tests showed that blood magnesium levels were below normal, fluctuating between 0.51-0.55 mmol/L; After oral administration of " oxcarbazepine" and " magnesium sulfate", convulsions improved and blood magnesium concentration increased, but remained below normal, with the highest being 0.61 mmol/L. The sequencing results of the whole exome display of the family showed that the child carried a heterozygous deletion mutation in the exon region of the CNNM2 gene (c.838_843delATGGCCp. M280-A281del), which was not detected in their parents, indicating a new mutation. The large-scale population frequency database gnomAD did not include this mutation, and no literature reported this mutation. According to the ACMG guidelines, it was rated as a suspected pathogenic variant. The pathogenic variation of this gene can lead to autosomal dominant HOMGSMR1, which was consistent with genetic patterns.Conclusions:CNNM2 gene c. 838_ 843delATGGCC (p.M280_A281del) is a suspected pathogenic variant in this patient, with genotype and phenotype matching and heterozygous mutations following genetic patterns. Autosomal dominant inheritance is the molecular cause of clinical manifestations in this patient, and it is an unreported novel mutation.