[A large family of Nascimento form of syndromic X-linked intellectual developmental disorder caused by large segment deletion of the gene: a case report and literature review].

This article reports the clinical features and gene mutation types of a large family with Nascimento form of syndromic X-linked intellectual developmental disorder (MRXSN), involving 9 individuals across 3 generations, and a literature review was conducted. In this family, 9 individuals had similar manifestations including mental retardation and unusual facies, and 4 of them had passed away. Genetic testing showed that the proband had the deletion of exons 2-3 of the gene, which was inherited from the mother. Fluorescent quantitative polymerase chain reaction showed that the proband and his uncle had the deletion of exons 2-3 of the gene; the proband's mother, grandmother, and great-aunt had a heterozygous deletion of exons 2-3 of the gene; the proband's father, sister, and aunt had a normal copy number of exons 2-3 of the gene. The 34 patients reported in the literature had diverse clinical phenotypes, and gene mutations (22/34, 65%) and large fragment deletions (12/34, 35%) were the main mutation types. Moderate to severe mental retardation (34/34, 100%), speech and language impairment (33/34, 97%), and unusual facies (32/34, 94%) were the main clinical manifestations of MRXSN patients. The disease has obvious phenotypic heterogeneity, and early diagnosis facilitates optimal prenatal and postnatal management to improve reproductive outcomes.