Department of Neurology, National Center Hospital, National Center of Neurology and Psychiatry, Tokyo, Japan.
Department of Neurology, Saku Central Hospital, Nagano Prefectural Federation of Agricultural Cooperatives for Health and Welfare, Nagano, Japan.
J Neuromuscul Dis. 2020;7(2):193-201. doi: 10.3233/JND-190440.
Paramyotonia congenita (PC; OMIM 168300) is a non-dystrophic myotonia caused by mutations in the SCN4A gene. Transient muscle stiffness, usually induced by exposure to cold and aggravated by exercise, is the predominant clinical symptom, and interictal persistent weakness is uncommon.
We report a family with a history of PC accompanied by persistent hand muscle weakness with masticatory muscle involvement. Persistent weakness was exacerbated with age, and MR analysis showed marked atrophy of temporal, masseter, and finger flexor muscles with fatty replacement. The PC causative mutation T1313M in the SCN4A gene was prevalent in the family. Administration of acetazolamide chloride improved clinical symptoms and the results of cold and short exercise tests. Phenotypic variation within the family was remarkable, as the two younger affected patients did not present with persistent weakness or muscle atrophy.
PC associated with the T1313M mutation is a possible cause of persistent distal hand weakness.
先天性肌强直症（PC；OMIM 168300）是一种非营养不良性肌强直，由 SCN4A 基因突变引起。主要的临床症状是短暂性肌肉僵硬，通常由寒冷诱发，运动加重，阵挛性持续性无力不常见。
我们报告了一个家族性 PC 病例，伴有持续性手部肌肉无力，咀嚼肌受累。持续性无力随年龄增长而加重，磁共振分析显示颞肌、咬肌和手指屈肌明显萎缩伴脂肪替代。SCN4A 基因中的 PC 致病突变 T1313M 在该家族中普遍存在。乙酰唑胺治疗改善了临床症状和冷、短运动试验结果。家族内的表型变异显著，因为两名年轻的受影响患者没有出现持续性无力或肌肉萎缩。
携带 T1313M 突变的 PC 可能是导致持续性手部远端无力的原因。
