IQSEC2 and X-linked syndromal intellectual disability

Area of Science:

• Genetics
• Neuroscience
• Developmental Biology

Background:

• Intellectual disability (ID) affects millions globally, with its genetic causes remaining elusive in about half of cases.
• Distinguishing syndromal from nonsyndromal ID is clinically vital but challenging.
• The genetic basis for the higher prevalence of ID in males is not fully understood.

Observation:

• This review systematically analyzes X-linked ID cases linked to de novo loss-of-function mutations in IQSEC2.
• IQSEC2 is primarily known for causing nonsyndromal ID in males.
• Phenotypic variability in IQSEC2-related ID ranges from nonsyndromal to severe syndromic forms in both sexes.

Findings:

• Truncation of IQSEC2 protein isoforms may disrupt cell signaling pathways, leading to syndromic ID.
• Key clinical features include global developmental delay, social communication deficits, hypotonia, and stereotyped hand movements.
• Seizures, microcephaly, and language regression are frequently observed in affected individuals.

Implications:

• Testing for IQSEC2 mutations is recommended for patients with this specific symptom profile, irrespective of sex, when no other genetic cause is identified.
• This expands the diagnostic potential for intellectual disability.
• Further research into IQSEC2's role in neurodevelopment is warranted.