AM Report Pearls: Approach to Asplenic Patients
Who are the Asplenic Patients? Broad Categories:
- Hematologic disorders (refractory thrombocytopenia, hereditary spherocytosis, primary myelofibrosis, hairy cell leukemia, refractory AIHA as in Evan’s syndrome)
o Note: Pearl from Harry: You are actually much more likely to get accessory spleens or splenic implants following splenectomy for trauma rather than hematologic causes (ITP, autoimmune hemolytic anemia).
- Functional Asplenia (e.g. splenic atrophy after repeated splenic infarctions from sickle cell disease)
What Vaccines for People with Asplenia?
- REQUIRED: Hib vaccine, Meningococcal vaccine, Pneumococcal vaccine
- USUAL TIMELINE IF INDICATED: Hep A, Hep B, Tdap, flu vaccine, polio, rotavirus, varicella, zoster
What Organisms to Worry About in Asplenic Patients?
- Bacterial – encapsulated organisms – S. pneumo, H. flu, N. meningitides
- Parasitic – Malaria, babesiosis, ehrlichiosis
- Viral – Case reports of severe CMV infections
AM Report Pearls: Approach to Hemolytic Anemia
- RBC hemolysis results from damage to the RBC membrane. SEVERE damage leads to intravascularhemolysis. Less severe damage leads extravascular hemolysis.
o Intravascular hemolysis = RBCs lysed within the vasculature!
o Causes include:
- Shearing: MAHAs or defective mechanical heart valves
- Complement mediated destruction: PNH, some drug reactions, ABO incompatibility, rarelyAIHA from cold agglutins (IgM)
- RBCs destroyed in the vasculature–>hemoglobinemia–>hemoglobinuria.. NOT seen in extravascular hemolysis. Chronic heme loss in the urineàconcomitant Fe deficiency anemia!
o Extravascular hemolysis = RBCs destroyed/phagocytosed by macrophages in the liver, spleen, bone marrow, and lymph nodes
o Causes include:
- Immune hemolytic anemia: RBCs coated in IgG, complement, or IgM+complement are phagocytosed in liver, spleen. Partial membrane phagocytosis–>microspherocytes!
- RBC membrane deformities: poorly deformable RBCs get stuck in sinusoids/cords of Billroth then phagocytosed. Ex: hereditary spherocytosis, G6PD def, thalassemia
- All components of RBCs are recycled, including Fe, so you don’t get an Fe deficiency anemia
Hemolysis Labs – seen in intra and extravascular hemolysis
- LDHreleased from lysed RBCs. Free Hg binds to haptoglobin reducing its serum concentration.
o Combo of increased LDH + reduced haptoglobin = 90 percent specific for diagnosing hemolysis
o Combo of a normal LDH + haptoglobin >25 mg/dL = 92 percent sensitive for ruling out hemolysis
- Direct Antibody Test(Coombs): for immune mediated hemolytic anemia. Detects IgG or complement on RBCs.
o In IgM mediated hemolysis, will only detect complement bound to IgM, not the IgM itself!