Affiliations: [a] Department of Neurology, National Center Hospital, National Center of Neurology and Psychiatry, Tokyo, Japan
| [b] Department of Neurology, Saku Central Hospital, Nagano Prefectural Federation of Agricultural Cooperatives for Health and Welfare, Nagano, Japan
| [c] Department of Neurology, Kuwana City Medical Center, Mie, Japan
| [d] Department of Radiology, National Center Hospital, National Center of Neurology and Psychiatry, Tokyo, Japan
| [e] Department of Genome Medicine Development, Medical Genome Center, National Center of Neurology and Psychiatry, Tokyo, Japan
| [f] Department of Neuromuscular Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
Correspondence to: Madoka Mori-Yoshimura, Department of Neurology, National Center Hospital, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8551, Japan. Tel.: +81 341 2711; Fax: +81 342 1852; E-mail: [email protected].
Abstract: Background: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. Case report: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. Conclusions:PC associated with the T1313M mutation is a possible cause of persistent distal hand weakness.
Keywords: Paramyotonia congenita, persistent distal hand weakness, temporal muscle, strabismus, SCN4A, T1313M, short exercise test, acetazolamide chloride