In cases where SCAs are not present in family history or where family history is unavailable, testing for the 4 most common SCAs will return positive results for 50% of suspected SCA cases. : 11  Individuals who are at risk of inheriting SCA1 but are currently presymptomatic can also be screened with molecular genetic testing. Genetic testing
Genetic testing is the only definitive way to differentiate between spinocerebellar ataxia types because of the similarity between clinical characteristics of these diseases and the large  variance between cases. Genetic testing is available for many SCA types, including the relatively common types SCA1, 2, 3, 6, and 7; and the less common SCA8, 10, 12, 14, and 17. However, genetic testing is high in cost and has a low diagnostic yield, with positive diagnoses being found in only 24% of tests ordered by a subspecialist and 10% overall.Genetic testing can be administered at various stages of disease progression. When genetic testing is administered after the onset of symptoms, the test is said to be diagnostic; in adults prior to onset of symptoms it is presymptomatic, and the test can be performed for prenatal or preimplantation diagnoses. The European Molecular Quality Genetics Network (EMQN) recommends criteria for each type, which must be met before testing can begin. The EQMN recommends that labs receive a written clinical evaluation of symptoms by a neurologist and a disclosure of family history, or lack of history, before initiating diagnostic genetic testing.
Familial thoracic aortic aneurysm and aortic dissection is a very rare vascular genetic disorder, its characterized by recurrent thoracic aortic aneurysms and aortic dissections within a family, these mentioned complications affect one or more aortic segments without any other disease being associated with them. People with this disorder have a higher chance of having a potentially fatal aortic rupture. This disorder is the cause of 20% of thoracic aortic aneurysmsSome families affected by this condition have shown mild versions of some symptoms that are associated with Marfan syndrome and Loeys-Dietz syndrome, these signs include tall stature, joint hypermobility, cutaneous stretch marks, and either pectus excavatum or pectus carinatum. Less common symptoms in other affected families include scoliosis, congenital heart defects, inguinal hernia, and/or livedo reticularis. Etiology
This disorder is caused by mutations in one or more of the following genes:
FOXE3 (located on 1p33)
SMAD2 (located on 18q21.1)
LOX (located on 5q23.3-31.2)
MAT2A (located on ? ??) ELN (located on chromosome 7)
HEY2 (located on 6q22.31)
TGFB3 (located on 14q24.3)
TGFBR1 (located on 9q22.33)
TGFBR2 (located on 3p24.1)
FBN1 (located on 15q21.1)
ACTA2 (located on 10q23.31
MYLK (located on 3q21.1)
SMAD3 (located on 15q22.33)
PRKG1 (located on 10q11.23-q21.1)
MFAP5 (located on 12p13.31)
TGFB2 (located on 1q41)
SMAD4 (located on 18q21.2)
MYH11 (located on 16p13.11)This disorder is inherited in an autosomal dominant manner, meaning only one copy of a mutated gene is needed in order for the disease to develop. == References ==