A DM1 patient with CCG variant repeats: reaching the diagnosis

Cumming, S. A., Oliwa, A., Stevens, G., Ballantyne, B., Mann, C., Razvi, S., Longman, C., Monckton, D. G. and Farrugia, M. E. (2021) A DM1 patient with CCG variant repeats: reaching the diagnosis. Neuromuscular Disorders, 31(3), pp. 232-238. (doi: 10.1016/j.nmd.2020.12.005) (PMID:33546847)

Abstract

We report the case of a male patient presenting in his 50s with ptosis, facial and distal limb muscle weakness, clinical and electrical myotonia, and a prior history of cataract extraction. He had a dominant family history in keeping with a similar phenotype. Myotonic dystrophy type 1 was clinically suspected. Triplet-primed polymerase chain reaction in a diagnostic laboratory did not identify a typical CTG repeat expansion on two separate blood samples. However, subsequent genetic testing on a research basis identified a heterozygous repeat expansion containing CCG variant repeats. Our case highlights the point that variant repeats are not detectable on triplet-primed polymerase chain reaction and result in a milder phenotype of myotonic dystrophy. It is crucial to maintain a high clinical index of suspicion of this common neuromuscular condition.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Monckton, Professor Darren and Longman, Dr Cheryl and Cumming, Dr Sarah and Razvi, Dr Saif and Ballantyne, Dr Bob and Mann, Dr Cameron
• Authors: Cumming, S. A., Oliwa, A., Stevens, G., Ballantyne, B., Mann, C., Razvi, S., Longman, C., Monckton, D. G., and Farrugia, M. E.
• College/School: College of Medical Veterinary and Life Sciences > School of Molecular Biosciences; College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience; College of Medical Veterinary and Life Sciences > School of Medicine, Dentistry & Nursing
• Journal Name: Neuromuscular Disorders
• Publisher: Elsevier
• ISSN: 0960-8966
• ISSN (Online): 1873-2364
• Published Online: 18 December 2020
• Copyright Holders: Crown Copyright © 2020
• First Published: First published in Neuromuscular Disorders 31(3): 232-238
• Publisher Policy: Reproduced in accordance with the publisher copyright policy