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

To explore the genetic basis for two Chinese pedigrees affected with Huntington disease and provide prenatal diagnosis for them.

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.

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.

Genetic testing can facilitate the diagnosis of Huntington disease and avoid further birth of affected children.