SMA is a rare, monogenic, neurodegenerative disorder that is often delayed in its diagnosis1,2

Spinal muscular atrophy (SMA) is the number 1 genetic cause of death in infants3

SMA is a disease caused by the deletion of the survival motor neuron 1 (SMN1) gene. It is characterized by a progressive loss of motor neurons, missed motor milestones, and, in its most severe forms, a high mortality.2,4

Understanding SMA Type 1

While there are multiple types of SMA, SMA Type 1 is the most common and one of the most severe forms of the disease.4
Though infants with SMA Type 1 may appear normal at birth, weakness can present within the first few months of life as rapid denervation occurs.5,6

Clinical features of SMA Type 1 include:

aEvent-free survival for Finkel et al=no death or no need for 16 hours/day ventilation continuously for 2 weeks, in the absence of an acute reversible illness; n=23 (2 copies of SMN2).9
bEvent-free survival for Kolb et al=no death or no tracheostomy; n=20.10

Don’t miss the narrow therapeutic window for SMA Type 1

Because infants with SMA may present with nonspecific symptoms, physicians may often take a “wait and see” approach to diagnosis11

Overlooking early symptoms and prolonging a patient’s diagnostic journey may result in missing a critical window for stopping the progression of SMA Type 1. As the loss of motor neurons is irreversible, early diagnosis and treatment are essential for improving patient outcomes.12

Genetic testing is the gold standard for diagnosing SMA3

In healthy individuals, the SMN1 gene produces full-length, functional SMN protein. However, patients with SMA rely on an SMN1 backup gene, SMN2, which produces only 10% functional SMN protein.4

A genetic test can confirm a homozygous mutation of the SMN1 gene3

SMN2 is considered a prognostic indicator for disease type and severity due to copy number variations. Having fewer copies of SMN2 is correlated with a more severe phenotype.8,13

Additional testing can confirm SMN2 copy number14

AveXis offers the AveXis Laboratory Program to facilitate SMA genetic testing and anti-AAV9 antibody testing

Proper SMA care requires a multidisciplinary care team

In addition to regular well visits with their pediatrician, patients may require respiratory, nutritional, and musculoskeletal support. These fundamental elements of SMA care can help maximize functional ability for those with all types of SMA.14,15