Infection and sickle cell anemia

Sickle cell disease is associated with frequent and often severe infections as a result of immune function impairment and functional asplenia. Also, infection can trigger a vasoocclusive crisis. Pneumococcal bacteremia and meningitis are so severe as to warrant prophylactic penicillin therapy, which has provided a dramatic decrease in early mortality. Bacterial pneumonia is common in patients younger than four years, with most cases being due to S. pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, and Chlamydia pneumoniae. Acute chest syndrome is both a difficult differential diagnosis and a common concomitant of bacterial pneumonia. Osteomyelitis is generally due to a salmonella, most often S. enteritidis; multiple foci are common and treatment is difficult, with some patients developing chronic osteomyelitis with sequestration. Parvovirus B 19 infection causes acute bone marrow failure. Malaria does not result in cerebral malaria but can lead to severe anemia or vasoocclusive crisis, and should therefore be effectively prevented. Antimicrobials are generally selected for efficacy against pneumococci (septicemia, meningitis), Salmonella (septicemia, meningitis, osteomyelitis), and mycoplasmas (pneumonia). Prophylactic therapy is of paramount importance and relies on long-term or lifelong penicillin therapy started at four months of age and on closely-spaced immunizations, most notably against pneumococci, the hepatitis B virus, S. typhi, and H. influenzae. Resistant pneumococcal strains have not been reported to cause prophylactic treatment failures. Conjugated pneumococcal vaccines are effective in protecting infants and should therefore be used in sickle cell patients.