Cautions and Warnings
For carrier testing and prenatal diagnosis the patient must have undergone proper counselling through the established national protocol for Huntington Disease Testing.
Referral reason plus adequate information and family history must be submitted with the specimen. Pedigree must be included where appropriate.
Huntington disease is an inherited autosomal dominant disease that gives rise to progressive selective (localised) neural cell death associated with choreic movements and dementia.
Increases in the length of a CAG triplet repeat, called 'Huntington' located on Chromosome 4p16.3 are associated with the clinical disease. There is an inverse relationship between repeat length and age of onset, the higher in frequency of juvenile onset cases arising from paternal transmission. The normal range of repeat sizes is between 5-30 whereas 30-36 is considered an intermediate range where the risk of developing clinical disease is undetermined. Affecteds usually have allele size greater than 37 repeats.
Please contact Molecular Genetics (APH Ext 22009) for further information.