spinal muscular atrophy
Genetic neuromuscular disorder caused by motor neuron degeneration, leading to progressive muscle weakness and atrophy.
Full Definition
Spinal muscular atrophy (SMA) is a group of hereditary neuromuscular disorders characterized by degeneration of motor neurons in the spinal cord anterior horn, resulting in progressive muscle weakness and atrophy. The most common form is caused by homozygous deletion or mutation of the survival motor neuron 1 (SMN1) gene. SMA is classified into types 0-4 based on age of onset and maximum motor function achieved, with Type I (Werdnig-Hoffmann disease) being the most severe infantile form. Clinical features include floppy infant syndrome, delayed motor milestones, and respiratory complications. Recent therapeutic advances include antisense oligonucleotides, gene therapy, and SMN2 splice modulators, significantly improving outcomes especially when treatment begins early.
Usage
Usage note: SMA abbreviation widely accepted; specify type when relevant (e.g., SMA Type I).
In Context
- "Genetic testing confirmed spinal muscular atrophy type II with homozygous SMN1 gene deletion." — Genetic counseling report
- "Early treatment with nusinersen improved motor outcomes in this infant with spinal muscular atrophy." — Clinical case report