OBJECTIVES : Although spinal muscular atrophy (SMA) is commonly known as a pediatric disease, adults comprise more than 50% of the prevalent SMA population. We aimed to evaluate the clinical and ambulatory characteristics of adult patients with SMA prior to the availability of disease modifying therapies.

METHODS : This retrospective, multi-country (United States, France, Germany, Italy, Spain, United Kingdom) study collected real-world natural history data on patients ≥18 years old, diagnosed with SMA prior to January 1, 2012 and managed by participating physicians from January 1, 2012 - December 31, 2016. Demographic and clinical data were abstracted from medical records and analyzed descriptively.

RESULTS : 339 adult patients (66% male) with SMA were included from 76 sites, of whom 74% had their diagnosis confirmed by genetic testing. Mean (range) follow-up was 11 (2-46) years from diagnosis to most recent visit; mean age was 31 (18-79) years at most recent visit, and mean age of symptom onset was 15 (1-69) years. At last visit 26% of patients had ≥1 comorbidity, most commonly diabetes and chronic pulmonary disease, and proximal muscle weakness (98%) and hypotonia (72%) were the most common clinical findings. At diagnosis, 81% of patients were ambulatory (able to take any steps independently with or without assistive devices); by last visit only 44% were ambulatory. From diagnosis to most recent visit there was an increase in prevalence of scoliosis by 22%, joint contractures by 25%, and muscle atrophy by 26%. As of last visit, 61% were unemployed, 54% of patients lived with a parent, and 44% relied on a parent as the primary caregiver.

CONCLUSIONS : Among adult patients with SMA, a significant proportion suffered loss of ambulation, and the occurrence of scoliosis increased post SMA diagnosis. These data demonstrate substantial burden on patients and families and the importance of treating this patient population.

Supported by: Biogen