Introduction: The purpose of this study was to reveal the prevalence, characteristics, and associations of pain with spinal muscular atrophy (SMA) type II in Japan.

Methods: A self-reported questionnaire was mailed to the patients with SMA type II. The questionnaire contained questions regarding the patients’ demographic and clinical characteristics, motor function, pain prevalence, location, frequency, and severity, precipitating and relieving factors.

Results: The questionnaire response rate was 61.1%. For the analysis, 64 patients with type II SMA or their families who fully completed the questionnaire were included. The median age of the included patients was 15.8 years (range, 3–55 years). Of the patients, 36% reported having current pain and 92% had persistent pain for at least 3 months. The pain sites most commonly reported were the legs (65.4 %) and neck/back (42.3 %). Excessive sitting and vigorous physical activity induced the pain, whereas taking a rest, postural change, and massage reduced the pain. A significantly greater proportion of patients in the pain group than in the non-pain group could not sit without using the hands for support (p = 0.03).

Conclusion: Our study showed that approximately one-third of the patients with type II SMA had long-term pain in their legs or neck/back. Physical stress such as that from prolonged sitting posture or excessive physical activity might be risk factors of pain in type II SMA.