Huntington’s disease: HD as an inherited neurodegenerative disease is characterized by the loss of GABAergic inhibitory spiny projection neurons in the striatum [94] due to abnormally elongated poly-glutamine (polyQ) stretch encoded by the atypical expansion of adenine, cytosine, and guanine (CAG) trinucleotide repeats at the huntingtin protein (Htt). The gene discussed is HTT; the disease is Huntington disease.