Pearls on Asplenia & Hemolysis Redux

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).

  • Trauma
  • 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!

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