Maeshima Shinichiro, Takeda Akinori, Sakurai Keita, Osawa Aiko, Arai Hidenori
Education and Innovation Center, National Center for Geriatrics and Gerontology, Obu, JPN.
Neurology, National Center for Geriatrics and Gerontology, Obu, JPN.
Cureus. 2025 Jul 29;17(7):e89002. doi: 10.7759/cureus.89002. eCollection 2025 Jul.
Myotonic dystrophy type 1 (DM1) is a multisystem autosomal dominant disorder primarily characterized by myotonia and distal muscle weakness. Central nervous system (CNS) involvement, including cognitive, executive, and emotional dysfunctions, is increasingly being recognized; however, language impairment as an initial presentation is rare. A 50-year-old right-handed woman with a six-month history of progressive word-finding difficulty, vague speech, and social withdrawal was referred for evaluation. Neurological examination revealed distal muscle atrophy (grip strength: 5 kg right, 8 kg left) without overt dysarthria or dysphagia, and intact reflexes and coordination. Neuropsychological testing revealed fluent spontaneous speech with anomia, semantic paraphasia, impaired comprehension of longer sentences, and surface dyslexia/agraphia (Mini-Mental State Examination-Japanese: 22/30, Frontal Assessment Battery: 8/18, Raven's Colored Progressive Matrices: 28/36, Montreal Cognitive Assessment-Japanese: 21/30). Brain magnetic resonance imaging revealed left-sided frontotemporal and limbic atrophy, and Tc-ethyl cysteinate dimer single-photon emission computed tomography showed a corresponding left-dominant hypoperfusion. Amyloid positron emission tomography (PET) scan results were negative. Two weeks later, percussion and grip myotonia emerged. Genetic analysis revealed a cytosine-thymine-guanine repeat expansion (~1500 repeats) in the myotonic protein kinase 1 gene, confirming the diagnosis of DM1. The patient's semantic-variant primary progressive aphasia-like profile (impaired semantic processing with preserved fluency) and frontotemporal imaging findings were consistent with rare CNS phenotypes reported in DM1. Previous studies have described frontotemporal atrophy, hypoperfusion, and cognitive/emotional changes in DM1. Negative amyloid PET excluded Alzheimer-related primary progressive aphasia. The subsequent detection of myotonia and a positive family history were key to diagnosis. We conclude that this case expands the clinical spectrum of DM1 to include progressive aphasia as an initial manifestation. Clinicians should maintain a high suspicion of neuromuscular disorders and actively pursue targeted genetic testing when atypical aphasia symptoms are accompanied by distal muscle atrophy.
1型强直性肌营养不良（DM1）是一种多系统常染色体显性疾病，主要特征为肌强直和远端肌肉无力。中枢神经系统（CNS）受累，包括认知、执行和情感功能障碍，越来越受到认可；然而，以语言障碍作为初始表现的情况很少见。一名50岁右利手女性，有6个月进行性找词困难、言语含糊和社交退缩的病史，被转诊进行评估。神经系统检查发现远端肌肉萎缩（握力：右侧5kg，左侧8kg），无明显构音障碍或吞咽困难，反射和协调功能正常。神经心理学测试显示自发流利言语伴有命名性失语、语义性错语、对较长句子的理解受损以及表层失读症/失写症（简易精神状态检查表 - 日语版：22/30，额叶评估量表：8/18，瑞文彩色渐进矩阵测验：28/36，蒙特利尔认知评估 - 日语版：21/30）。脑磁共振成像显示左侧额颞叶和边缘叶萎缩，锝 - 乙基半胱氨酸二聚体单光子发射计算机断层扫描显示相应的左侧优势灌注减低。淀粉样蛋白正电子发射断层扫描（PET）结果为阴性。两周后，出现叩击性和握力性肌强直。基因分析显示强直性肌营养不良蛋白激酶1基因中有胞嘧啶 - 胸腺嘧啶 - 鸟嘌呤重复序列扩增（约1500次重复），确诊为DM1。患者的语义变异型原发性进行性失语样表现（语义处理受损但流利性保留）和额颞叶影像学表现与DM1中报道的罕见CNS表型一致。先前的研究描述了DM1中的额颞叶萎缩、灌注减低以及认知/情感变化。淀粉样蛋白PET阴性排除了阿尔茨海默病相关的原发性进行性失语。随后肌强直的发现和阳性家族史是诊断的关键。我们得出结论，该病例将DM1的临床谱扩展至包括以进行性失语作为初始表现。当非典型失语症状伴有远端肌肉萎缩时，临床医生应高度怀疑神经肌肉疾病并积极进行靶向基因检测。
