Passeri Elena, Sansone Valeria A, Verdelli Chiara, Mendola Marco, Corbetta Sabrina
Endocrinology and Diabetology Unit, Dept. Biomedical Sciences for Health, University of Milan, IRCCS Policlinico San Donato, San Donato M.se, Milan, Italy.
NEuroMuscular Omnicentre (NEMO), Fondazione Serena Onlus, Dept. Biomedical Sciences for Health, University of Milan, Milan, Italy.
Neuromuscul Disord. 2014 Apr;24(4):365-7. doi: 10.1016/j.nmd.2014.01.006. Epub 2014 Jan 24.
Myotonia congenita is an inherited muscle disorder sustained by mutations in the skeletal muscle chloride channel gene CLCN1. Symptoms vary from mild to severe and generalized myotonia and worsen with cold, stressful events and hormonal fluctuations. Here we report the case of a young woman who sought medical attention because of subacute onset of diffuse and severe limb myotonia. CLCN1 gene sequencing showed a heterozygous transversion (T550M), two polymorphisms and one silent mutation. Thyroid function screening revealed severe hypothyroidism. She was placed on l-thyroxine replacement therapy which dramatically improved myotonia. We conclude that hypothyroidism unmasked a genetically determined, clinically asymptomatic chloride channelopathy. Diagnostic work-up in patients with clinically isolated myotonia should not be limited to genetic screening of non-dystrophic or dystrophic myotonias. Considering the high prevalence of hypothyroidism in females, systematic thyroid function screening by looking for additional hypothyroid symptoms and serum TSH levels measurement is mandatory in these patients.
先天性肌强直是一种遗传性肌肉疾病，由骨骼肌氯离子通道基因CLCN1的突变引起。症状从轻度到重度不等，表现为全身性肌强直，在寒冷、应激事件和激素波动时会加重。在此，我们报告一例年轻女性病例，该患者因亚急性发作的弥漫性严重肢体肌强直而就医。CLCN1基因测序显示杂合性颠换（T550M）、两个多态性和一个沉默突变。甲状腺功能筛查显示严重甲状腺功能减退。她接受了左甲状腺素替代治疗，肌强直症状得到显著改善。我们得出结论，甲状腺功能减退症掩盖了一种由基因决定的、临床上无症状的氯离子通道病。对于临床上孤立性肌强直患者的诊断检查不应局限于非营养不良性或营养不良性肌强直的基因筛查。鉴于女性甲状腺功能减退症的高患病率，在这些患者中通过寻找其他甲状腺功能减退症状和测量血清促甲状腺激素水平进行系统的甲状腺功能筛查是必要的。
