UGT1A1 and Hyperbilirubinemia: Though the role of p.(Pro451Leu) in UGT1A1 isoenzyme activity has not been reported, sorting intolerant from tolerant and polymorphism phenotyping analyses [14] and the correlation of phenotype-genotype observed in our pedigrees make it persuasive that this mutation was the cause of unconjugated hyperbilirubinemia.