Paramyotonia congenita in a Slovak population: Genetic and pedigree analysis of 3 families.

BACKGROUND: Paramyotonia congenita is a non-dystrophic myotonia, in which muscle relaxation is delayed after voluntary or evoked contraction. This condition cannot be distinguished on the basis of symptoms and signs alone. It requires consideration of genetics as more than 100 mutations in the CLCN1 gene and at least 20 mutations in the SCN4A gene are associated with the clinical features of the non-dystrophic myotonias. Only a few families with the described features but no genetic testing have been reported in Slovakia. This prompted us to investigate genetic mutations in the SCN4A gene in 3 Slovak families clinically diagnosed with paramyotonia.

SUBJECTS AND METHODS: Genomic DNA of the family members was extracted from peripheral blood and amplified by polymerase chain reaction. SCN4A variants were screened by Sanger sequencing.

RESULTS: Our results revealed 2 potential disease-causing mutations present in the probands and affected family members - mutations c.3938C > T (p.T1313M) in two families and mutation c.2111C>T (p. T704M) in one family.

CONCLUSION: Our results may help to identify genetic determinants as well as clarify genotype-phenotype relationships in patients with paramyotonia in Slovakia.