As in other AIDs, the carrier rate of 1/350 in normal population allowed to hypothesize a selective advantage for heterozygous carriers; a possible explanation postulates that countries with a diet at high consumption of saturated animal fats rich in cholesterol could have selected heterozygous carriers of the most frequent MVK mutations (30); nevertheless, this theory has not been demonstrated and other possible explanations are possible. The gene discussed is MVK; the disease is AIDS.