Assuming CHH and ITP each exerts its distinct function through interacting with different receptor, there should be residues responsible for functional divergence between the 2 peptides of Group I. In this regard, the second position is the only one where residues (Ile2/Phe2) have been experimentally demonstrated to be implicated in functionally differentiating CHH from ITP. The gene discussed is RMRP; the disease is autoimmune thrombocytopenic purpura.