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Expanding the Phenotypic Spectrum of Trafficking Protein Particle Complex Subunit 9-Related Intellectual

Maha Ben Jemaa1, Haifa El Mabrouk2,3, Mona Mahfood1

  • 1Human Genetics and Stem Cell Laboratory, Research Institute of Sciences and Engineering, University of Sharjah, Sharjah, United Arab Emirates.

Genetic Testing and Molecular Biomarkers
|July 8, 2026
PubMed

Insights

Intellectual Disability-Obesity-Brain Malformations-Facial Dysmorphism Syndrome is linked to TRAPPC9 gene mutations. Genetic testing is crucial for diagnosing Prader-Willi-like syndrome and guiding treatment.

Area of Science:

  • Genetics
  • Neurology
  • Rare Diseases

Background:

  • Intellectual Disability-Obesity-Brain Malformations-Facial Dysmorphism Syndrome (IDOB-FMD) is a rare autosomal recessive disorder.
  • Characterized by intellectual disability, microcephaly, brain abnormalities, obesity, and facial dysmorphism.
  • Shares clinical similarities with Prader-Willi syndrome (PWS).

Purpose of the Study:

  • To investigate the genetic basis of Prader-Willi-like syndrome (PWLS) in two Tunisian siblings.
  • To identify genetic variants associated with the observed phenotype using whole-exome sequencing (WES).

Main Methods:

  • Clinical evaluation of two siblings with suspected PWLS.
  • Whole-exome sequencing (WES) for genetic variant identification.
  • Variant interpretation and segregation analysis to confirm pathogenicity.

Main Results:

  • WES identified a homozygous mutation in the TRAPPC9 gene in both siblings.
  • The identified TRAPPC9 variant was predicted to be pathogenic and segregated with the phenotype.
  • Clinical findings were consistent with PWLS, including intellectual disability and microcephaly.

Conclusions:

  • Genetic testing is vital for patients with PWLS features.
  • A TRAPPC9 mutation was identified, expanding the known mutational spectrum for this condition.
  • Findings offer insights into clinical management, genetic counseling, and genotype-phenotype correlations for TRAPPC9-related disorders.
Abstract

Keywords:
Prader–Willi-like syndromeTRAPPC9 deficiencygenetic testingintellectual disabilitywhole-exome sequencing

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