Natural history of Southeast Asian Ovalocytosis during the first 3 years of life.

Southeast Asian Ovalocytosis (SAO), the most common red cell membrane disorder found in the Far-East and Pacific rim, appears to be innocuous in man since it has been identified mostly in non-anemic healthy individuals. To further substantiate our previous observation that this condition might be symptomatic particularly in the neonatal period, we studied 1567 newborns from Southern Thailand where SAO is prevalent. Thirty-one babies (1: 50 with allele frequency of 0.01) have been identified with SAO and confirmed molecularly to carry a single defective AE-1 (band 3) allele. These babies had significant anemia at birth due to hemolysis with 51.6% of them developing neonatal hyperbilirubinemia. Co-inheritance of common UGT1A1 variants in such cases was not associated with their degree of jaundice. Interestingly, hematology data of these SAO babies became "normalized" in the first 3 years of life without further evidence of on-going and/or even "compensated" hemolysis.