背景:常染色体隐性遗传性先天性肌强直症(Becker病)是由CLCN1基因突变引起的。该病症的特征在于持续肌肉收缩期间的肌肉僵硬和随着反复收缩而趋于改善的可变程度的肌肉无力。
方法:一名21岁男子自过去10年以来出现短暂的肌肉僵硬。他难以开始运动,休息后肌肉无力,这通常改善后反复收缩(热身现象)。没有明显的家族史。体检显示全身肌肉肥大。血清肌酸激酶水平比正常值高2倍。肌电图显示肌强直放电。DNA序列分析确定了一个新的剪接突变(c.1401+1G>A)和一个已知的突变(c.1657A>T,P.Ile553Phe)。他对美西律100mg治疗迅速反应,每天3次,持续6个月。
结论:本病例报道了一种新型复合杂合突变引起的常染色体隐性遗传性先天性肌强直症,扩展了CLCN1基因的基因型谱。
BACKGROUND: Autosomal recessive Myotonia congenita (Becker\'s disease) is caused by mutations in the CLCN1 gene. The condition is characterized by muscle stiffness during sustained muscle contraction and variable degree of muscle weakness that tends to improve with repeated contractions.
METHODS: A 21-year-old man presented with transient muscle stiffness since the last 10 years. He had difficulty in initiating movement and experienced muscle weakness after rest, which typically improved after repeated contraction (warm-up phenomenon). There was no significant family history. Medical examination showed generalized muscle hypertrophy. Serum creatine kinase level was 2-fold higher than the normal value. Electromyogram showed myotonic discharges. DNA sequence analysis identified a novel splice mutation (c.1401 + 1G > A) and a known mutation (c.1657A > T,p.Ile553Phe). He rapidly responded to treatment with mexiletine 100 mg three times a day for 6 months.
CONCLUSIONS: This
case report of autosomal recessive Myotonia congenita caused by a novel compound heterozygous mutation expands the genotypic spectrum of CLCN1 gene.