It was first described by George Huntington in 1872. Genetically, it is an autosomal dominant disorder with complete penetrance. The mutation, CAG-trinucleotide repeats, may expand in descendent generations explaining anticipation. Progression is relentless usually ending in death within 10-20 years. However the contribution of the mutant form of huntington is presently unclear.
Gene imprinting explains the transmission of the childhood form primarily through the father.
Eventually progresses to include dementia and slowed eye movements. In juvenile HD, rigidity and parkinsonian tremor may be the primary manifestation. The most significant neuropathological change is a preferential loss of medium spiny neurons in the neostriatum. Biochemically there is marked loss of GABA, substance P, enkephalin, angiotension converting enzyme. Neuronal changes begin very early in life, perhaps even from birth.