To characterize the diagnostic and treatment journey of adults living with SMA Type 4.

Spinal muscular atrophy (SMA) is a neuromuscular disease that leads to varying degrees of muscle atrophy. SMA Type 4 presents in adults and is the rarest SMA subtype. Timeline to diagnosis and treatment utilization of individuals with SMA Type 4 is not well-described in the literature. Although SMA newborn screening has been adopted across the United States, individuals born prior to implementation rely on symptomatic diagnosis.

A survey was developed and distributed from March 2025–July 2025 to adults with self-reported SMA Type 4 within a non-profit owned membership database.

14 complete, unique responses were included in analysis. The average age of symptom onset was 28.4 years. Symptoms that triggered respondents seeking medical care included change in stride (57%), muscle fatigue with movement (57%), and gradual weakening of arms and legs (57%). 49% reported their time to diagnosis following initial evaluation was more than two years. 50% of respondents indicated evaluation by a specialist unfamiliar with SMA was a barrier to timely diagnosis. 36% of respondents report they were initially misdiagnosed with a condition other than SMA Type 4. 57% of respondents reported utilization of an FDA-approved treatment at any point since diagnosis. 43% reported utilization of FDA-approved treatment at time of survey completion. 50% reported insurance-related issues when attempting to access treatment.

This research provides insight into the diagnostic and treatment journey of adults living with SMA Type 4. Although a variance was reported, a subset of respondents experienced diagnostic delays exceeding 2 years. Continuing education detailing the clinical presentation and diagnostic criteria for adult-onset SMA may improve provider awareness and patient outcomes. Future research should explore real-world treatment experiences, access barriers, and unmet needs of the population to inform treatment decision-making and payor advocacy.