Interestingly, the majority of CHH reported thus far, like Sco-CHH, has at the second position a hydrophobic residue without aromatic ring (Ile, Leu, Val, or Ala), whereas ITP always has a Phe2 (Fig 6), which has an aromatic side chain. This evidence concerns the gene RMRP and autoimmune thrombocytopenic purpura.