However, the potentially negative long term consequences associated with this approach should not be underestimated, as it is also apparent that the permanent lack of PCSK9 may reduce the ability of the liver to regenerate68 and may enhance viral infections.101,102 Furthermore, the extreme rarity of individuals that completely lack PCSK9 is if anything, an indication of a potential counter-selection against this event during evolution. This evidence concerns the gene PCSK9 and viral infectious disease.