LPL and hyperkeratosis lenticularis perstans: Assuming a frequency of LPL deficiency of one in a million, then a frequency of obligate heterozygotes for mutation in the LPL gene of 0.2% is to be expected and so it cannot be ruled out that individually rare mutations in the LPL gene collectively play a role in the development of Type III HLP in APOE2/2 individuals.