<prompt> Hemolytic crisis in hereditary spherocytosis is precipitated byParvovirus B19 infectionInfectious mononucleosisHuman T-cell leukemia virusCytomegalovirus  <response>: Ans. a Parvovirus B19 infectionRef: Harrison 18thpg 1478Aplastichypoplastic crises resulting from parvovirus B19 infection may occur in Hereditary spherocytosis just as is seen in individuals with other chronic hemolytic disorders.Parvovirus B19 selectively infects erythroid precursors and inhibits their growth.Erythropoietic arrest leads to a sudden decrease in hemoglobin concentration and reticulocytopenia. 