Phenotype-genotype correlations in patients with congenital myotonia Becker
DOI:
https://doi.org/10.67667/NEU.v24i2.140Keywords:
CLCN1-gene, myotonia, myotonic phenomenonAbstract
Myotonia congenita (MC) is a genetic neuromuscular channelopathy that affects skeletal muscle fibers. It is caused by mutations in the CLCN1 gene, encoding the skeletal muscle chloride channel ClC-1. (7q35). Myotonia, defined as a delay or failure of relaxation in contracted skeletal muscle, is considered to be the hallmark of the disease and results in prolonged rigidity which is clinically presented in stiffness, cramping and muscle hypertrophy.
Purpose: To present phenotype-genotype correlations in Bulgarian patients with myotonia congenita Becker.
Мethods: neurological examination, electromyography, echocardiography, electrocardiography, spirometry, CPK, Timed Up and Go test and Time-stands test.
Results: Clinical examination – myotonia and muscle hypertrophy were found in all cases. The „warm-up effect” may also be demonstrable. Еlectromyography demonstrated a shower of spontaneous electrical activity in diffuse myotonic discharges or „bursts”. In 6 cases elevations of creatinine kinase have been described up to two times the upper limit of normal.
Conclusion: Affected individuals describe muscular stiffness upon initiating movement. The stiffness remits with several repetitions of the same movement, giving rise to the so-called warm-up phenomenon.
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Copyright (c) 2023 Stanislava Blagoeva, Teodora Chamova, Ivailo Tournev
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