What Your Test Results Mean:

Carriers typically show no symptoms of Andermann syndrome; however, carriers are at an increased risk of having a child with Andermann syndrome. Risk for the current or future pregnancies is dependent on your partner’s carrier status. Carrier testing of your partner is recommended in addition to consultation with a genetic counselor.

Disease Explained:

Andermann syndrome is an inherited disorder characterized by nerve damage, resulting in abnormal or absent reflexes, weak muscle tone, muscle wasting, severe progressive weakness and loss of sensation in the limbs, and tremors. Individuals with Andermann syndrome typically walk late and then lose the ability to walk in their teenage years. As they get older, people with this disorder frequently develop joint deformities, which restrict the movement of certain joints, as well as scoliosis, which may require surgery.

Andermann syndrome also results in abnormal function of certain cranial nerves, which emerge directly from the brain and extend to various areas of the head and neck. Cranial nerve problems may result in facial muscle weakness, drooping eyelids, and difficulty following movements with the eyes. Individuals with Andermann syndrome usually have intellectual disability, which may be mild to severe, and some experience seizures. They may also develop psychiatric symptoms such as depression, anxiety, agitation, paranoia, and hallucinations, which usually appear in adolescence. There is no cure for Andermann syndrome. Physical therapy may be useful to maintain movement as long as possible.

How the Genetics Works:

Andermann syndrome is an autosomal recessive disorder caused by pathogenic variants in the SLC12A6 gene. The SLC12A6 gene is involved in the production of the protein K-Cl cotransporter. This protein is critical for the development and maintenance of nerve tissue. A lack of function K-Cl cotransporter, due to SLC12A6 variants, can interfere with the development of the corpus callosum and maintenance of the nerves that transmit signals needed for movement and sensation. All individuals have two copies of the SLC12A6 gene. Carriers of Andermann syndrome have a variant in one copy of the SLC12A6 gene while individuals with Andermann syndrome have variants in both copies of the SLC12A6 gene, one inherited from each parent. Risk for two carriers to have a child with the disorder is 25%.