BACKGROUND: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is rare among 
Japanese ethnicity although it is known as one of the most common hereditary 
disorders of erythrocytes, causing intravascular hemolysis. It is well-known 
that G6PD deficiency may cause hemolysis even in the neonatal period. However, 
most cases are asymptomatic, and the frequency of severe anemia is low.
FINDINGS: We describe a Japanese male neonatal case of G6PD deficiency 
presenting as severe, persistent indirect hyperbilirubinemia on day 2 and 
hemolytic anemia. He was born to non-consanguineous Japanese parents without any 
family history. We could not find any triggers that could have induced hemolysis 
during pregnancy.
CONCLUSIONS: This case encouraged us to investigate G6PD deficiency as a 
differential diagnosis of severe neonatal jaundice and hemolytic anemia despite 
the low prevalence in Japan.