Recessive CLCN1 mutation presenting as Thomsen disease
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Updated: Jun 30, 2026

In Vivo Functional Study of Disease-associated Rare Human Variants Using Drosophila
Published on: August 20, 2019
Judy Thomas1, Jack Tarleton2, Steven K Baker1
1Department of Medicine, Physical Medicine & Neurology, Neuromuscular Disease Clinic, Rm 2H22, McMaster University Medical Centre, McMaster University, Hamilton, Ontario, L8N 3Z5, Canada.
Abstract:
This case report describes a young man referred for electrodiagnostic evaluation for hand stiffness and intermittent numbness. His needle electromyography revealed diffusely increased insertional and spontaneous motor activity in the form of myotonic discharges. Given the finding of symptomatic myotonia also in his mother, Thomsen myotonia was suspected. Investigations not only confirmed Thomsen myotonia, but also led to the identification of a previously reported heterozygous Becker mutation in both the proband and his mother.
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