Unveiling New Clinical and Genetic Insights in Ultra-Rare Intellectual Disability Phenotypes: A Study of a Turkish...

Area of Science:

• Genetics
• Pediatrics
• Neurology

Background:

• Intellectual disability (ID) is a neurodevelopmental disorder characterized by impaired reasoning and adaptive behaviors before age 18.
• Ultrarare ID phenotypes are exceptionally uncommon, with fewer than 20 cases reported in the literature.
• Understanding the genetic basis of ultrarare ID is crucial for diagnosis and management.

Purpose of the Study:

• To present the clinical and genetic data of Turkish pediatric patients with ultrarare intellectual disability.
• To identify novel genetic variations and expand the genotypic and phenotypic spectrum of ultrarare ID.
• To contribute to a better understanding of the molecular mechanisms underlying these rare conditions.

Main Methods:

• Whole exome sequencing (WES) was performed on 29 pediatric patients from 26 families diagnosed with ultrarare ID.
• Genetic variations were analyzed, including missense, nonsense, frameshift, splice-site, and gross exonic deletions.
• Copy number variations (CNVs) analysis and in silico modeling were utilized to assess the impact of variations on protein structure.

Main Results:

• A total of 28 different genetic variations were identified across 23 distinct genes in the cohort.
• Nine (32%) of the detected variations were novel, expanding the known genetic landscape of ultrarare ID.
• Consanguinity was present in 55% of families, suggesting a potential role in recessive inheritance patterns.

Conclusions:

• This study provides valuable clinical and genetic insights into 23 different ultrarare ID phenotypes.
• The identification of novel variations contributes to a more comprehensive understanding of the genotypic and phenotypic spectrum of ID.
• The findings aid in clarifying clinical manifestations and molecular mechanisms of rare intellectual disability syndromes.