How many people are affected by Huntington disease-like syndrome ?
Overall, HDL syndromes are rare. They are much less common than Huntington disease, which affects an estimated 3 to 7 per 100,000 people of European ancestry.  Of the four described HDL syndromes, HDL4 appears to be the most common. HDL2 is the second most common and occurs almost exclusively in people of African heritage (especially black South Africans). HDL1 has been reported in only one family. HDL3 has been found in two families, both of which were from Saudi Arabia.