RESUMO
Spinocerebellar ataxia type 2 (SCA2, OMI health, reproductive, financial matters, and183090) belongs to a group of hereditary family planning. Therefore, we undertook a sur-neurodegenerative diseases caused by the expan- vey of the age of onset in a cohort of SCA2sion of a CAG repeat tract in coding regions of patinovel genes. This group includes Huntingtonsdisease (HD), spinal and bulbar muscularatrophy (SBMA), dentatorubral-pallidoluysianatrophy, and the spinocerebellar ataxias type 1,3, 6, 7, and 17 (1). These mutations show a veryhigh penetrance, and they follow an autosomaldominant inheritance pattern with the onlyexception of SBMA (X-linked); each descendantof an affected patient has an a priori risk of 50%.However, it has been proven that the empiric riskof having inherited the mutation causing HD orSCA3 (MachadoJoseph disease) lessens withadvancing age (2, 3). This fact has significantimplications in the genetic counseling of at-riskindividuals. The accuracy and precision that areachieved in the estimate of the risk of developinga certain hereditary illness will have a very...(AU)