The central role of p16INK4a in melanocyte biology is demonstrated by the fact that individuals with familial CDKN2A gene (encoding p16INK4a and p14ARF) deficiency (also known as Leiden syndrome or Familial Atypical Multiple Mole Melanoma syndrome) have a characteristic accumulation of nevi and an increased melanoma risk [351]. The gene discussed is CDKN2A; the disease is familial atypical multiple mole melanoma syndrome.