[Genetic testing and prenatal diagnosis of two pedigrees affected with Huntington disease].

OBJECTIVE: To explore the genetic basis for two Chinese pedigrees affected with Huntington disease and provide prenatal diagnosis for them. METHODS: Peripheral venous blood samples were collected from the probands. PCR and capillary gel electrophoresis were used to determine the number of CAG repeats in their IT15 gene. Pre-symptomatic testing was offered to their children and relatives, and prenatal diagnosis was provided to three pregnant women from the two pedigrees. RESULTS: The two probands, in addition with three asymptomatic members, were found to have a (CAG)n repeat number greater than 40. Upon prenatal diagnosis, the numbers of CAG repeats in two fetuses from pedigree 1 were determined as (16, 19) and (18, 19), both were within the normal range. A fetus from pedigree 2 was found to have a CAG repeat number of (15, 41), which exceeded the normal range. CONCLUSION: Genetic testing can facilitate the diagnosis of Huntington disease and avoid further birth of affected children.