ABOUT SMA / WHAT IS SMA?

SMA progression is continuous1-3

SMA is a genetic, progressive neuromuscular disease2,4

SMA is a neurodegenerative disease that results in the deterioration of motor function and muscle strength over time, due to loss of motor neurons in the CNS.2,3,5

Natural history studies of SMA show that progression is a threat across disease type, although the rate and severity can vary.2

Watch to learn more about the causes and symptoms of SMA.

Mechanism of disease

Watch the video to learn about the clinical manifestations and cause of SMA.

The broad range of SMA symptoms includes6:

  • Weakness that is usually symmetrical and more proximal than distal
  • Absent or diminished tendon reflexes
  • Difficulty or inability to walk
  • Respiratory issues that may require tracheostomy or ventilation

SMA is caused by a lack of functional SMN protein5

Two nearly identical genes produce SMN protein4

People with SMA have a homozygous deletion or heterozygous mutation of their SMN1 gene, and rely on the SMN2 gene to produce functional SMN protein. However, only about 10% of SMN2 pre-mRNA is translated into full-length SMN protein, which is needed to support the survival and function of motor neurons. This results in the progressive loss of strength and motor function that patients with SMA experience.2,4,5

Because motor function loss progresses over time, it is important that patients receive an accurate diagnosis and speak with a healthcare professional about treatment options.2

Why it’s important to consider treating SMA as soon as possible

Motor function loss may be permanent and unpredictable2,7,8

Motor neuron loss is irreversible, leading to progressive muscle weakness, motor function impairment, and disability.
SMA progression can go unnoticed for years2,7,9

For adults with later-onset SMA, it can be hard to recognize progression. Genetic testing can help accurately diagnose SMA, while continued monitoring can help measure progression.

CNS, central nervous system; mRNA, messenger ribonucleic acid; SMA, spinal muscular atrophy; SMN, survival motor neuron; SMN1, survival motor neuron 1; SMN2, survival motor neuron 2.
Genetic testing can confirm an SMA diagnosis or SMA carrier status.10

Motor neuron loss and muscle weakness in SMA

LEARN ABOUT SMA AND MUSCLE HEALTH
LEARN ABOUT AN SMA TREATMENT

INDICATION

SPINRAZA® (nusinersen) is indicated for the treatment of spinal muscular atrophy (SMA) in pediatric and adult patients.

IMPORTANT SAFETY INFORMATION

Coagulation abnormalities and thrombocytopenia, including acute severe thrombocytopenia, have been observed after administration of some antisense oligonucleotides. Patients may be at increased risk of bleeding complications.

In the sham-controlled studies for patients with infantile-onset (Study 1) and later-onset (Study 2) SMA who received Low Dose Regimen (12 mg loading doses/12 mg maintenance doses), 24 of 146 SPINRAZA-treated patients (16%) with high, normal, or unknown platelet count at baseline developed a platelet level below the lower limit of normal, compared to 10 of 72 sham-controlled patients (14%). Two SPINRAZA-treated patients developed platelet counts <50,000 cells per microliter, with the lowest level of 10,000 cells per microliter recorded on study day 28. In patients who received High Dose Regimen (50 mg loading doses/28 mg maintenance doses), decreases in platelet counts were also observed.

Renal toxicity, including potentially fatal glomerulonephritis, has been observed after administration of some antisense oligonucleotides. SPINRAZA is present in and excreted by the kidney. In Study 1 and Study 2, 71 of 123 SPINRAZA-treated patients (58%) had elevated urine protein, compared to 22 of 65 sham-controlled patients (34%).

Laboratory testing and monitoring to assess safety should be conducted. Perform a platelet count, coagulation laboratory testing, and quantitative spot urine protein testing at baseline and prior to each dose of SPINRAZA and as clinically needed.

Severe hyponatremia was reported in an infant treated with SPINRAZA requiring salt supplementation for 14 months.

Cases of rash were reported in patients treated with SPINRAZA.

SPINRAZA may cause a reduction in growth as measured by height when administered to infants, as suggested by observations from the controlled study. It is unknown whether any effect of SPINRAZA on growth would be reversible with cessation of treatment.

The most common adverse reactions in the Low Dose Regimen (≥20% of SPINRAZA-treated patients and ≥5% more frequently than in control patients) that occurred in the infantile-onset controlled study were lower respiratory infection and constipation. Serious adverse reactions of atelectasis were more frequent in SPINRAZA-treated patients (18%) than in control patients (10%). Because patients in this controlled study were infants, adverse reactions that are verbally reported could not be assessed. The most common adverse reactions that occurred in the later-onset controlled study were pyrexia, headache, vomiting, and back pain. Post-lumbar puncture syndrome has also been observed after the administration of SPINRAZA.

The most common adverse reactions in the High Dose Regimen (≥10% of SPINRAZA-treated patients and ≥5% more frequently than control patients from Study 1) that occurred in patients with infantile-onset SMA were pneumonia, COVID-19, pneumonia aspiration, and malnutrition. COVID-19 was not discovered at the time of Study 1.

Please see full Prescribing Information.

As a courtesy, our full Prescribing Information is also available en Español. For prescribing decisions, please refer to official approved labeling.

References

1. Montes J, McDermott MP, Mirek E, et al. Ambulatory function in spinal muscular atrophy: age-related patterns of progression. PLoS One. 2018;13(6):e0199657. doi:10.1371/journal.pone.0199657 2. Wadman RI, Wijngaarde CA, Stam M, et al. Muscle strength and motor function throughout life in a cross-sectional cohort of 180 patients with spinal muscular atrophy types 1c-4. Eur J Neurol. 2018;25(3):512-518. doi:10.1111/ene.13534 3. Werlauff U, Vissing J, Steffensen BF. Change in muscle strength over time in spinal muscular atrophy types II and III. A long-term follow-up study. Neuromuscul Disord. 2012;22(12):1069-1074. doi:10.1016/j.nmd.2012.06.352 4. Lunn MR, Wang CH. Spinal muscular atrophy. Lancet. 2008;371(9630):2120-2133. doi:10.1016/S0140-6736(08)60921-6 5. National Library of Medicine. MedlinePlus: SMN1 gene. Updated October 1, 2018. Accessed March 19, 2026. https://ghr.nlm.nih.gov/gene/smn1 6. Wang CH, Finkel RS, Bertini ES, et al. Consensus statement for standard of care in spinal muscular atrophy. J Child Neurol. 2007;22(8):1027-1049. doi:10.1177/0883073807305788 7. Prior TW, Leach ME, Finanger EL. Spinal muscular atrophy. 2000 Feb 24 [Updated 2026 Feb 12]. In: Adam MP, Bick S, Mirzaa GM, et al, editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2026. 8. Stifani N. Motor neurons and the generation of spinal motor neuron diversity. Front Cell Neurosci. 2014;8:293. doi:10.3389/fncel.2014.00293 9. Mercuri E, Lucibello S, Pera MC, et al. Long-term progression in type II spinal muscular atrophy: a retrospective observational study. Neurology. 2019;93(13):e1241-e1247. doi:10.1212/WNL.0000000000008166 10. D’Amico A, Mercuri E, Tiziano FD, Bertini E. Spinal muscular atrophy. Orphanet J Rare Dis. 2011;6:71. doi:10.1186/1750-1172-6-71

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