Currently, there are no established guidelines on premedication for RCM-induced anaphylaxis15; however, corticosteroid prophylaxis remains the standard of care in the United States.16 Both oral and parenteral steroids are often administered in combination with H1-antihistamine and H2-histamine receptor blockers; however, these regimens cannot ensure complete prevention of RCM-induced anaphylaxis. The gene discussed is HRH2; the disease is anaphylaxis.