A 39-year-old male presented to our hospital for an annual complete medical checkup (so-called human dock in Japanese). He had a 10-year history of malaise. Physical examination revealed frontal balding (Figure 1) and grip myotonia (sustained muscle contraction; Figure 2 and Supplementary (Video). Spirometry suggested restrictive ventilatory impairment (vital capacity percentage, 65.6%; forced expiratory volume in 1 second as forced vital capacity percentage, 86.6%). Further workup investigation was performed because myotonic dystrophy was suspected. Laboratory studies revealed a mildly elevated creatine phosphokinase level of 224 U/L (non-disease associated range, 24–195 U/L). Electromyography showed myotonic discharges in the right biceps muscle. Although the patient's family history was unremarkable, dystrophia myotonica protein kinase (DMPK) genetic testing revealed a CTG repeat expansion of 400 (non-disease associated range <35), confirming the diagnosis of myotonic dystrophy type 1 (DM1). Regular follow-up showed no signs and symptoms of critical complications (i.e., cardiac arrhythmia, cataract, and endocrine abnormalities).
To read this article in full you will need to make a payment
Purchase one-time access:Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
One-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:Subscribe to The American Journal of the Medical Sciences
Already a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
- The myotonic dystrophies: molecular, clinical, and therapeutic challenges.Lancet Neurol. 2012; 11: 891-905
- The myotonic dystrophies: diagnosis and management.J Neurol Neurosurg Psychiatry. 2010; 81: 358-367
- Differential diagnosis of myotonic disorders.Muscle Nerve. 2008; 37: 293-299
Published online: January 14, 2022
Accepted: January 4, 2022
Received: June 23, 2021
© 2022 Southern Society for Clinical Investigation. Published by Elsevier Inc. All rights reserved.