COMT and hearing loss disorder: Similarly, SNPs of thiopurine S-methyltransferase (TPMT) and catechol O-methyltransferase (COMT), which encodes enzymes that metabolize thiopurine drugs (Weinshilboum, 2006) and catecholamine containing chemical via methylation (Weinshilboum, 2006), respectively, predispose the pediatric population to increased risk of hearing loss (Ross et al., 2009) after cisplatin therapy.