Interfamilial phenotypic heterogeneity in SMARD1

Area of Science:

• Genetics
• Neurology
• Pediatrics

Background:

• Spinal muscular atrophy with respiratory distress (SMARD1) is a severe genetic disorder.
• It is caused by mutations in the IGHMBP2 gene.
• SMARD1 typically presents before 13 months with respiratory failure and limb weakness.

Observation:

• This case report details two siblings with identical SMARD1 mutations.
• One sibling experienced fatal respiratory failure at 6 months.
• The other sibling, aged 12, exhibits limb weakness and mild sleep hypoventilation.

Findings:

• The identical genetic mutation resulted in significantly different clinical outcomes.
• Phenotype variability in SMARD1 is more pronounced than previously understood.
• This suggests the influence of modifying genes or environmental factors.

Implications:

• SMARD1 should be considered in atypical spinal muscular atrophy cases, even without clear diaphragmatic weakness.
• Understanding phenotype variability can improve diagnostic approaches and patient management.
• Further research into compensatory mechanisms in SMARD1 is warranted.