Myotonia congenita
Definition
Pathogenic variants in the CLCN1 gene impair the function of the skeletal muscle ClC-1 chloride channel; this channel dysfunction leads to delayed relaxation after contraction (myotonia). Autosomal dominant Thomsen disease is rarer and milder, while autosomal recessive Becker disease is more common and generally more severe; muscle stiffness and the 'warm-up' phenomenon occur in both forms.
Gene/region analyzed
CLCN1 - Exon 1, CLCN1 - Exon 2, CLCN1 - Exon 3, CLCN1 - Exon 4, CLCN1 - Exon 5, CLCN1 - Exon 6, CLCN1 - Exon 7, CLCN1 - Exon 8, CLCN1 - Exon 9, CLCN1 - Exon 10, CLCN1 - Exon 11, CLCN1 - Exon 12, CLCN1 - Exon 13, CLCN1 - Exon 14, CLCN1 - Exon 15, CLCN1 - Exon 16, CLCN1 - Exon 17, CLCN1 - Exon 18, CLCN1 - Exon 19, CLCN1 - Exon 20, CLCN1 - Exon 21, CLCN1 - Exon 22, CLCN1 - Exon 23
Method
Sequence analysis
Accepted sample types
EDTA blood, AF, CVS
Inheritance
Hereditary, both autosomal dominant (Thomsen) and autosomal recessive (Becker) forms exist.