Usually associated with parvovirus B19 infection in those with hereditary spherocytosis

Ans. is 'b' i.e., Aplastic crisis Parvovirus B19 selectively infects erythroid precursors and is the most common aetiological agent that induces aplastic crisis in patients with hereditary spherocytosis (and other Hemolytic disorders). Transient aplastic crisis Persons with decreased erythrocytes caused by conditions such as iron deficiency anemia, human immunodeficiency virus sickle cell disease, spherocytosis or thalassemia are at risk of transient aplastic crisis if infected with parvovirus B19. The virus causes a cessation of erythrocyte production. Parvovirus infection may be the first manifestation in HS. It begins with reticulocytosis and thrombocytosis