Marked hyperbilirubinemia associated with the heme oxygenase-1 gene promoter microsatellite polymorphism in a boy with autoimmune hemolytic anemia.

Mild hyperbilirubinemia is a clinical feature of hemolysis. Here we describe a boy with marked elevation of serum bilirubin values ( maximum: 70 mg/ dL) during an acute episode of autoimmune hemolytic anemia, which returned to within the reference range after clinical improvement. The boy was a homozygous carrier of short alleles of the heme oxygenase- 1 ( HO- 1) gene GT dinucleotide- repeat promoter polymorphism, which is associated with increased activity and inducibility of the heme- degrading enzyme HO- 1, which catalyzes the production of bilirubin. In addition, heterozygosity of the uridine 5'-diphosphate- glucuronosyl- transferase 1A1 promoter polymorphism that is linked with Gilbert syndrome was found in this patient. Because bilirubin production plays a critical role during the neonatal period, the HO- 1 promoter polymorphism may be an important genetic factor for the clinical outcome of neonatal hyperbilirubinemia.