Asplenia

Question 1

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I. Causes of Asplenia

Answer 1

Surgical removal (e.g., after trauma)
• Sickle cell disease → autosplenectomy (repeated infarctions)
• Hereditary spherocytosis → often requires splenectomy
• Congenital asplenia (rare)

Question 2

High-Yield Functions of the Spleen

Answer 2

• Filters encapsulated bacteria via opsonization
• Stores and removes senescent RBCs
• Contains splenic macrophages and marginal zone B cells → rapid antibody response to polysaccharide antigens

Step 1 Tip: Loss of spleen = impaired clearance of encapsulated organisms (especially without opsonization).

Question 3

Most Commonly Tested Pathogens

Answer 3

Asplenic patients are at high risk for severe infections by encapsulated organisms:

SHiN organisms:
1. Streptococcus pneumoniae (most lethal)
2. Haemophilus influenzae type B
3. Neisseria meningitidis

Other important organisms:
• Salmonella species
• Capnocytophaga canimorsus (dog bite in asplenic patient)
• Babesia (tick-borne parasite cleared by spleen)

Question 4

Clinical Clues on Step 1

Answer 4

• Sudden-onset sepsis in patient with sickle cell disease or history of splenectomy
• Rapid hypotension, DIC, shock after minor symptoms
• “Encapsulated organism” + “no spleen” = classic Step 1 pairing

Question 5

Vaccinations for Asplenic Patients

Answer 5

Crucial for Step 1!
Asplenic patients must be vaccinated against:

Pathogen
Vaccine Type

Strep. pneumoniae
PCV13 + PPSV23 (conjugate + polysac)

H. influenzae type B
Hib conjugate

Neisseria meningitidis
Meningococcal conjugate (and group B)

Step 1 Tip: These are all conjugate vaccines to induce a T-cell dependent response (important for long-term immunity).

Question 7

Antibiotic prophylaxis

Answer 7

Often given daily oral penicillin in young children with sickle cell disease
• Important during first few years of life or post-splenectomy

Question 8

Babesiosis in Asplenic Patients

Answer 8

• Clue: Northeastern US + hemolytic anemia + fever + asplenia
• Pathogen: Babesia microti (tick-borne)
• Blood smear: Maltese cross forms

Step 1 Tip: Asplenic + fever + hemolysis → think Babesia or severe malaria (if travel history).

Question 9

Tips

Answer 9

Buzzwords: “Sickle cell”, “post-trauma splenectomy”, “encapsulated organisms”, “vaccines”, “penicillin prophylaxis”
• Always ask: “Could this patient be functionally asplenic?”
• Remember that asplenic patients die quickly from pneumococcus → this is often the point of the question
• Be able to match pathogens to conjugate vaccines