[Molecular analysis of the IT15 gene in 79 Spanish families with Huntington's disease: diagnostic confirmation and presymptomatic diagnosis]. / Análisis molecular del gen IT15 en 79 familias españolas afectadas de enfermedad de Huntington: confirmación diagnóstica y diagnóstico presintomático.

BACKGROUND: Huntington's disease (HD) is a neurodegenerative disorder with late age of onset, caused by (CAG), expansion in the IT15 gene. We present here the results of IT15 gene study in Spanish families in order to show the usefulness of diagnosis, genetic counseling and clinical-genetic correlation in Spanish population. PATIENTS AND METHODS: We have studied the number of (CAG)n repeats in the IT15 gene by PCR analysis in 137 individuals from 79 Spanish families with HD. RESULTS: The number of (CAG)n repeats in HD chromosomes varied from 35 to 85, while the range for the normal chromosomes was from 13 to 31. In four juvenile cases the number of (CAG)n repeats was above 50. In three of these cases the transmission was paternal. The (CAG)n expansion was demonstrated in 98.3% of the cases. We established the diagnosis in 15 uncertain clinical diagnosis. We made a presymptomatic diagnosis after psychological-psychiatric evaluation in 50 HD at risk individuals. We showed an inverse correlation between the number of (CAG)n repeats and the age at onset of the disease. CONCLUSIONS: The (CAG)n repeats study in the IT15 gene in Spanish populations allows the confirmation of diagnosis of HD as well as presymptomatic testing enabling the genetic counseling. There is an inverse correlation between the age of onset of the disease and the number of (CAG)n repeats in the IT15 gene.