Tokyo-1 Mutation: Hereditary Spherocytosis in a Hispanic Newborn Presenting as Early Onset Severe Hyperbilirubinemia.

Background: Hereditary spherocytosis in the Hispanic population does not often present with severe hyperbilirubinemia. Spectrin and band 3 mutations are most frequent in this population. Case report We present a Hispanic full-term female newborn with early onset significant hyperbilirubinemia without a history of familial hemolytic disorders. She was diagnosed with hereditary spherocytosis based on laboratory findings, including presence of spherocytes on a peripheral smear, and was later found by next-generation sequencing to have Tokyo-1 mutation, an ANK1 gene mutation, that was previously only reported in Japanese population. Conclusion: Our report adds to the currently limited literature of the genetic spectrum and characteristics of hereditary spherocytosis in the Hispanic population. The absence of a positive family history does not preclude hereditary spherocytosis as a differential for pathologic neonatal hyperbilirubinemia.