[Genetic analysis of a case of Miller-McKusick-Malvaux syndrome type 1 caused by CUL7 gene variant and a literature review]

Abstract

Objective: To explore the clinical features, genetic characteristics in a child with Miller-McKusick-Malvaux syndrome (3MS) type 1 caused by CUL7 gene variant.

Methods: A child diagnosed with 3MS type 1 at the Children's Hospital Affiliated to Zhengzhou University in February 2021 was selected as the subject of this study. Peripheral blood samples were collected from the child and her parents for genomic DNA extraction. Whole exome sequencing (WES) was performed on the child, and Sanger sequencing was used to validate the candidate variants and analyze their pathogenicity. A literature search was conducted using the keywords "3M syndrome" in the China National Knowledge Infrastructure, Wanfang Data Knowledge Service Platform, and PubMed databases from inception to December 2024. The clinical data of Chinese children with 3MS reported in the literature were summarized. This study was approved by the Medical Ethics Committee of the Children's Hospital Affiliated to Zhengzhou University (Ethics No. 2024-K-020).

Results: The child was a 6-year-old and 2-month-old female with facial dysmorphism, skeletal abnormalities, and growth and developmental delay. WES revealed compound heterozygous variants in the CUL7 gene: c.2686G>T (p.E896*) and c.1200delT (p.R401Gfs66). Sanger sequencing confirmed that these two variants were inherited from the child's father and mother, respectively. According to the American College of Medical Genetics and Genomics (ACMG) Standards and Guidelines for the Interpretation of Sequence Variants, c.2686G>T (p.E896) was classified as a pathogenic (PVS1+PM2_Supporting+PM3), and c.1200delT (p.R401Gfs*66) was classified as a likely pathogenic (PVS1+PM2_Supporting). Based on the literature search strategy, 18 relevant articles were identified, including a total of 32 Chinese cases of 3MS, of which 8 were fetuses. A total of 32 Chinese 3MS cases were included in the literature review, of which 8 were fetuses. The majority of these cases carried variants in the CUL7 gene (20/32, 62.5%) and OBSL1 gene (12/32, 37.5%). The main clinical manifestations included intrauterine or postnatal growth and developmental delay (32/32, 100.0%), triangular facies (27/32, 84.3%), and skeletal abnormalities (21/32, 65.6%).

Conclusion: The compound heterozygous variants c.2686G>T (p.E896*) and c.1200delT (p.R401Gfs*66) in the CUL7 gene are likely the genetic cause of 3MS type 1 in the child. For children presenting with facial dysmorphism, skeletal abnormalities, and intrauterine or postnatal growth and developmental delay, 3MS should be considered as a differential diagnosis.