Background

International reporting of epidemiological surveys of spinal muscular atrophy (SMA) in Japan has been limited to Shikoku, despite the epidemiology of the disease in countries worldwide becoming clearer. Treatments of 5q-SMA have been developed, and epidemiological studies are needed.

Purpose

This study aimed to conduct a nationwide epidemiological survey of SMA in Japan to clarify the actual situation of SMA in Japan.

Method

Patients with all clinical types of SMA, including neonates and adults, were selected from 1,005 medical facilities in Japan.

Results

As of December 2017, the actual number of reported patients with SMA was 658 and the genetic testing rate was 79.5%. The estimated number of patients was 1,478 (95% confidence interval (CI), 1,122–1,834), with a prevalence of 1.17 (95%CI, 0.89–1.45) per 100,000 people and an incidence of 0.51 (95%CI, 0.32–0.71) per 10,000 live births. Incidence rates of 5q-SMA by clinical type were 0.27 (95%CI, 0.17–0.38) and 0.08 (95%CI, 0.04–0.11) per 10,000 live births for type 1 and 2, respectively, in cases with a definitive diagnosis by genetic testing. We found that 363 cases (82.7%) occurred less than 2 years and 88 (20.0%) occurred age of 2 months old or under.

Conclusion

This study clarifies the prevalence and incidence of SMA in Japan. As infantile onset accounts for most cases of SMA, newborn screening and subsequent treatment are important to save lives.

中文翻译：

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日本脊髓性肌萎缩症流行病学调查

背景

日本脊髓性肌萎缩 (SMA) 流行病学调查的国际报告仅限于四国，尽管世界各国对该病的流行病学越来越清楚。已经开发了 5q-SMA 的治疗方法，需要进行流行病学研究。

目的

本研究旨在对日本全国范围内的 SMA 进行流行病学调查，以明确日本 SMA 的实际情况。

方法

从日本的 1,005 家医疗机构中挑选出所有临床类型的 SMA 患者，包括新生儿和成人。

结果

截至2017年12月，实际报告的SMA患者为658人，基因检测率为79.5%。估计患者人数为 1,478 人（95% 置信区间 (CI)，1,122–1,834），患病率为每 100,000 人 1.17（95%CI，0.89–1.45），发病率为 0.51（95%CI，0.32– 0.71) 每 10,000 名活产婴儿。按临床类型分列的 5q-SMA 的发病率分别为 0.27（95%CI，0.17-0.38）和 0.08（95%CI，0.04-0.11）1 型和 2 型活产每 10,000 例活产，在确诊病例中基因检测。我们发现 363 例（82.7%）发生在 2 岁以下，88 例（20.0%）发生在 2 个月或以下。

结论

本研究阐明了日本 SMA 的患病率和发病率。由于婴儿发病占大多数 SMA 病例，因此新生儿筛查和后续治疗对于挽救生命很重要。