The Hammersmith functional score correlates with the SMN2 copy number: a multicentric study

Area of Science:

• Neurology
• Genetics
• Pediatric Neuromuscular Disorders

Background:

• Spinal muscular atrophy (SMA) is a genetic disorder characterized by progressive muscle weakness.
• The survival motor neuron gene 2 (SMN2) is a key determinant of SMA severity.
• Previous research indicates an inverse correlation between SMN2 copy number and SMA disease severity.

Purpose of the Study:

• To investigate the relationship between SMN2 copy number and functional motor impairment in patients diagnosed with SMA type II (SMA II).
• To determine if SMN2 gene quantity predicts the level of functional disability within the SMA II patient cohort.

Main Methods:

• Analysis of SMN2 gene copy numbers in 87 patients diagnosed with SMA II.
• Assessment of functional motor status using the Hammersmith functional motor scale (HFMS).
• Statistical evaluation to establish correlation between SMN2 copy number and HFMS scores.

Main Results:

• A significant correlation was observed between the number of SMN2 gene copies and the degree of functional impairment in SMA II patients.
• While functional scores exhibited some variability, the overall trend supported the link between SMN2 quantity and motor function.
• Patients with higher SMN2 copy numbers generally demonstrated better functional motor abilities.

Conclusions:

• SMN2 copy number is a significant predictor of functional motor outcomes in individuals with SMA II.
• Understanding this correlation can aid in predicting disease progression and tailoring therapeutic strategies for SMA II.
• The findings reinforce the importance of SMN2 gene quantity in modulating SMA II phenotype severity.