Diagnosis of congenital myotonia can as well be confirmed my molecular genetic analysis of ClCN-1 gene responsible for function of ClC-1 channels.<\/p>\n
Parents of a proband. <\/em>The majority of individuals diagnosed with autosomal dominant myotonia congenita have an affected parent. <\/em>A proband with autosomal dominant myotonia congenita may potentially have the disorder as the result of a new gene mutation. The proportion of cases caused by de novo is very low.<\/em><\/p>\n Sibs of a proband. <\/em>The risk to the sibs of the proband depends on the genetic status of the proband’s parents. If a parent of the proband is affected, the risk to the sibs is 50%. When the parents are clinically unaffected, the risk to the sibs of a proband appears to be low.<\/p>\n Offspring of a proband.<\/em> Each child of an individual with autosomal dominant myotonia congenita has a 50% chance of inheriting the mutation.<\/p>\n Other family members of a proband.<\/em> The risk to other family members depends on the status of the proband’s parents. If a parent is affected, his or her family members are at risk.<\/p>\n \u00a0Parents of a proband. <\/em>The parents of an individual with autosomal recessive myotonia congenita are obligate heterozygotes and therefore each carry one mutant allele. <\/em>Heterozygotes (carriers) are asymptomatic. Occasionally, the parents of a proband with autosomal recessive myotonia congenita show subtle evidence of myotonia on EMG testing.<\/p>\n \n Sibs of a proband. <\/em>At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier.<\/em><\/p>\n Offspring of a proband. <\/em>The offspring of an individual with autosomal recessive myotonia congenita are obligate heterozygotes (carriers) for a disease-causing mutation.<\/p>\n Other family members of a proband.<\/em> Each sib of the proband’s parents is at a 50% risk of being a carrier.<\/p>\n \u00a0Expert centers<\/em><\/p>\n\n