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)

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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:Cumming, Dr Sarah and Monckton, Professor Darren and Razvi, Dr Saif and Ballantyne, Dr Bob and Longman, Dr Cheryl 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 > Institute of Molecular Cell and Systems Biology
College of Medical Veterinary and Life Sciences > Institute of Neuroscience and Psychology
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

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