Spinal muscular atrophy

Spinal muscular atrophy is a group of inherited disorders in which loss of spinal motor neurons causes progressive muscle weakness and wasting. Most cases result from changes affecting the SMN1 gene.

SMN1: SMN1 is the gene that provides instructions for producing survival motor neuron protein. Loss or dysfunction of SMN1 causes most spinal muscular atrophy.
Nusinersen: Nusinersen is an antisense oligonucleotide medicine that increases production of functional SMN protein from SMN2. It is an established treatment that modifies SMN2 splicing.
Spinal muscular atrophy type 0: Spinal muscular atrophy type 0 is a rare, severe form with symptoms beginning before birth. It represents the earliest-onset end of the clinical spectrum.
Spinal and bulbar muscular atrophy: Spinal and bulbar muscular atrophy is an inherited X-linked disorder caused by an androgen-receptor gene expansion. Despite a similar name and motor-neuron symptoms, it has a different gene and inheritance pattern.
SMN2: SMN2 is a gene closely related to SMN1 that produces mostly incomplete survival motor neuron protein. Its small amount of full-length protein can moderate disease severity.
Onasemnogene abeparvovec: Onasemnogene abeparvovec is a gene-replacement therapy that delivers a functional SMN1 copy using an AAV9 vector. It addresses the underlying gene deficiency with a one-time infusion.
Spinal muscular atrophy type 1: Spinal muscular atrophy type 1 is an early-onset form that begins in infancy and causes severe weakness. It is a historically severe infantile presentation, though treatment changes outcomes.
Amyotrophic lateral sclerosis: Amyotrophic lateral sclerosis is a progressive neurodegenerative disease affecting upper and lower motor neurons. It also causes progressive weakness but is generally not the childhood-onset SMN1 disorder.
Survival motor neuron protein: Survival motor neuron protein is a cellular protein needed for motor-neuron maintenance and RNA processing. Insufficient functional protein is the central molecular defect in most cases.
Risdiplam: Risdiplam is an oral small-molecule medicine that modifies SMN2 splicing to increase functional SMN protein. It offers systemic treatment by altering the same gene's RNA processing.

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