The number of CAG codons varies and so does the severity of the disease
Age of onset varies based on the number of repeats.
The earliest onset of Huntington’s ever documented was a two year old boy who was found to have nearly 100 CAG repeats.
The symptoms of HD can also develop at 55 or later, in which case it is harder to recognize.
What is Juvenile Huntington’s Disease?
10% of Huntington’s cases.
Usually 80-100 CAG repeats
stiffness or rigidity in joints as opposed to chorea for adult-onset HD
1/3 of Juvenile HD patients have recurring seizures.
Believed to inherit large numbers of repeats from father.
How is Huntington’s Disease Diagnosed?
Symptoms are frequently recognized by people who have history with the disease, but for others there is testing.
Huntington’s can be diagnosed by a simple blood test at any age.
There are three types of tests that can be taken to determine an HD diagnosis:
The symptoms are caused by a loss of neurons in the brain that occurs about the time that disease becomes first manifest
The basal ganglia and cortex are ravaged, which can be followed up with a MRI or PET
In the caudate nucleus, populations of enkephalin and substance P containing medium-sized spiny GABAergic projection neurons are the first to be affected
The exhibit wilted and recurved dendritic endings and changes in the density, shape and size of the spines.
The large acetylcholine rich or smaller somatostatin and neuropeptide Y containing aspiny interneurons are spared by the disease process
It is this characteristic pattern of neuronal cell loss in the basal ganglia that forms the basis for the neurophathological grading of HD