Which of the following viruses most commonly causes aplastic crises in patients with sickle cell anemia?

Sickle cell patients are vulnerable to a variety of potentially life-threatening clinical crises. Impoant causes of aplastic crises (also called hematologic crises), in which the marrow fails to produce adequate numbers of erythrocytes, include parvovirus B19 infection and folate deficiency. For your personal information, although the question is usually asked about sickle cell anemia, these two inciting agents can also induce exacerbation of anemia in individuals with thalassemia and a variety of other hereditary red cell disorders. Simple transfusions can be used to treat aplastic crises. BK virus causes renal disease in immunocompromised hosts. Human herpes virus 8 has been implicated in Kaposi sarcoma. Human papilloma virus 18 is an impoant cause of cervical dysplasia and cancer. Ref: Ray C.G., Ryan K.J. (2010). Chapter 10. Mumps Virus, Measles, Rubella, and Other Childhood Exanthems. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e.