Following the description of the disease, several cases were identified, with a clustering of HD cases identified by Dr. Amerigo Negrette around Lake Maracaibo, in Venezuela [1], where a group of researchers identified the defective gene to be located in the first exon of the huntingtin gene on chromosome 4, which contained an expanded unstable CAG (cytosine-adenine-guanine) repeat [2]. The gene discussed is HTT; the disease is Huntington disease.