A 7-year-old boy with homozygous sickle cell disease develops fever and severe pain over the tibia. Blood culture grows Salmonella species. His susceptibility to this infection is best explained by:

• A Hydroxyurea induced neutropenia
• B Iron overload providing nutrition for intracellular bacteria in macrophages
• C Functional asplenia impairing clearance of encapsulated organisms and defective complement activation ✓
• D Loss of CD55 and CD59 from leukocyte surfaces

Explanation

Repeated splenic infarcts cause autosplenectomy, leaving patients unable to clear encapsulated bacteria such as Salmonella, Streptococcus pneumoniae, and Haemophilus influenzae. Sickle patients are uniquely prone to Salmonella osteomyelitis, possibly related to impaired complement mediated killing plus microinfarcted bone serving as a nidus. Iron overload favors Yersinia and Listeria, hydroxyurea causes macrocytosis not significant neutropenia at usual doses, and CD55/CD59 loss defines PNH.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.