A. Introduction

1. ~10-20 cases per million persons
2. Women more common than men (at least for autoimmune form)
3. Usually begins in mid-life (autoimmune form)
4. Requirements
   1. Shortened red blood cell (RBC) survival (normal half-life is ~120 days)
   2. Evidence of RBC destruction (antibodies, schistocytes, elevated RBC enzymes, etc)

B. Red Blood Cell (RBC) Changes [13]

1. Microspherocytes - most common change
2. Polychromasia - due to reticulocytes
3. Schistocytes - common in microangiopathic forms

C. Major Etiologies [2]

1. Autoimmune (AHA) [9]
   1. Coombs' Direct Antiglobin Positive, ~1 per 100,000 persons
   2. Idiopathic primary or associated with collagen vascular disease
   3. Neoplasm Associated: B cell neoplasm or immune response to other cancers
   4. Warm and cold types of antibodies are described
   5. Autoantibodies specific for RBC band III (anti-I/i) transporter protein are very common
   6. Cold agglutinin disease (~30% of cases of AHA) - usually with acrocyanosis, IgM Abs
   7. RBC glycophorin A and Rh-related proteins may also be targets of autoantibodies
   8. Evan's Syndrome - hemolytic anemia and thrombocytopenia (very rare)
   9. Major destruction is through splenic (and liver) sequestration
   10. FcR+ macrophages are responsible for phagocytosing
2. Associated with Infection (anti-RBC Antibodies)
   1. Most anti-RBC (erythrocyte) antibodies cause cold-agglutinin disease
   2. Associated with mycoplasma infections and infectious mononucleosis
   3. Cytomegalovirus also associated with these autoantibodies
   4. Hepatitis C (and sometimes B) Virus infection with cryoglobulinemia
   5. Cold agglutinins are associated with acrocyanosis
3. Transfusion associated (Coombs' Indirect Antiglobin Positive)
4. Structural Anomaly / Hemoglobinopathies
   1. Sickle Cell Anemia
   2. Spherocytosis (hereditary)
   3. Ovalocytosis
   4. Thalassemias
5. Intravascular Hardware
   1. Metal cardiac valves
   2. Some vascular synthetics
6. Medications
   1. Procainamide - very common (in addition to lupus-like reactions)
   2. Alpha-methyldopa (Aldomet®)
   3. Penicillin
   4. Oxacillin
   5. Cefotetan (Cefotan®)
   6. Ceftriaxone (Rocephin®) - very uncommon [3]
   7. Hydralazine
   8. Quinidine
7. Infectious Agents
   1. Malaria
   2. Babesiosis [2]
   3. Less Common: toxoplasmosis, leishmaniasis, trypanosomiasis
   4. Bacterial: bartonelllosis, clostirium, cholera, typhoid
8. Hemolytic Anemia associated with SLE [7]
   1. Hemolytic anemia occurs in ~10% of cases of SLE
   2. Hemolytic anemia is associated with renal involvement and thrombocytopenia
   3. Also associated with IgG anticardiolipin antibodies in SLE patients
   4. Following treatment initiation, recurrence of hemolytic anemia is rare
9. Microangiopathic
   1. Hemolytic Uremic Syndrome (HUS)
   2. Thrombotic Thrombocytopenic Purpura (TTP)
   3. Disseminated intravascular coagulopathy (DIC)
   4. Severe Pre-eclampsia (HELLP Syndrome)
10. PNH [9]
    1. Acquird mutations in X-linked PIG-A (phosphatidylinositol glycan protein A) gene
    2. Inability to anchor certain proteins through phosphatidylinositol membrane anchors
    3. Reduction in PI linked proteins on cell surface has many effects
    4. Major problem is lack of DAF (CD55) and CD59 on erythrocytes
    5. This leads to increased complement mediated lysis of erythrocytes
    6. Result is hemolytic anemia with usual problems (low HCT, elevated MCV)
    7. Usually occurs in middle aged persons; can also occur in children
    8. Previously diagnosed by increased RBC fragility (Ham's Test)
    9. Now diagnosed by flow cytometric analysis of CD55 and CD59 on RBCs
11. Paroxysmal Cold Hemoglobinuria
    1. Rare autoimmune disease in adults on cold exposure
    2. Associated with tertiary or congenital syphilis
    3. Post-Viral - children or young adults in most cases
    4. Antibodies against P bloodgroup antigen are induced
    5. May be associated with cold induced urticaria
    6. Generally self limited
12. Neonatal
    1. Hydrops fetalis is due to maternal anti-fetal RBC antibodies
    2. Most common fetal antigen is Rh-D in Rh-D negative mothers with D+ fetus
    3. Rh Status can be detected by molecular analysis of maternal plasma in >80% of cases [6]
    4. About 10% of neonatal hemolytic anemia is due to anti-Kell Abs [5]
    5. Kell system of antigens is also expressed on erythroid progenitor cells
13. Complicates ulcerative colitis in 0.5-2% [8]

D. Symptoms and Signs

1. Mainly related to low blood counts
   1. Fatigue
   2. Hypotension
   3. Palor
   4. High cardiac outputs leading to congestive heart failure
2. Hyperbilirubinemia may lead to jaundice
3. Chronic hemolysis may lead to bilirubin gallstone formation
4. Splenomegaly can occur due to increased red cell sequestration
5. Pulmonary Hypertension [4]
   1. Common complication of chronic hemolytic anemias due to hemoglobinopathies
   2. ~10% of patients with hemoglobinopathies develop moderate to severe PH [4]
   3. Severity of hemolysis correlates with degree of PH
   4. Symptoms occur when mean PAP reaches 30-40 mm
   5. Develops in 20-40% of sickle cell anemia (HbSS) patients [12]
   6. In HbSS, risk factor for complications, death [12]
   7. Focus on therapies that increase nitric oxide
   8. Sildenafil reduces pulmonary pressures and improves exercise tolerance in HbSS

E. Laboratory Diagnosis of Hemolytic Anemia

1. Increased reticulocyte count with peripheral nucleated red blood cells
2. Increased mean corpuscular volume (MCV), usually with anisocytosis
3. Coombs Direct Anti-globin Test
   [Figure] "Evaluation of Anemia"
   1. Positive in autoimmune and drug induced forms
   2. Measures Ig and/or complement C3d bound to patient's red blood cells (RBC)
   3. In cases of C3d and Ig association, consider diagnosis of systemic lupus (SLE)
   4. Coombs Indirect Anti-globin Test measures anti-RBC molecules in patient's sera
   5. Majority (~85%) of adults with AHA have Abs that work best at 37° ("warm" Abs)
   6. "Cold" Abs types are usually IgM and work best at <37°C (~12% of cases)
   7. Some patients have mixed warm and cold Abs (~3%)
   8. Acrocyanosis is a common presentation of cold-agglutinin disease
4. Hyperbilirubinemia, primarily unconjugated, due to increased hemoglobin release
5. RBC Enzymes: increased lactate dehydrogenase (LDH), aspartate aminotransferase (AST)
6. Reduced plasma haptoglobin and hemopexin levels (bind free hemoglobin and heme)

F. Treatment of Autoimmune Hemolytic Anemia

1. Glucocorticoids are mainstay of therapy
   1. Prednisone 0.6-2mg/kg po qd is usually recommended
   2. Continue for 2-3 weeks then begin taper (down to 30mg/d) if counts improve
   3. Better responses in children than in adults
   4. Gradual tapering, perhaps down to 15-30mg po qod then maintain for 6-9 months
   5. Glucocorticoids decrease macrophage Fc receptor expression and thus RBC clearance
   6. Overall ~80% initial response in adults, with ~20% complete responders
   7. For cold agglutinin disease, keeping patient warm is critical
2. Intravenous gammaglobulin (IVIg) may be helpful but is usually temporary
3. Plasmapheresis / Plasma exchange may be effective in temporarily removing antibodies
4. Recurrent Disease
   1. Danazol - a synthetic androgen, effective in some patients at 400-600mg po qd
   2. Rituximab (Rituxan®)
   3. Splenectomy - usually for failure to respond to (or side effects of) glucocorticoids
   4. Cytotoxic Agents (usually with glucocorticoids) - may reduce antibody titers
   5. Cyclosporine has also been effective
   6. Azathioprine - glucocorticoid sparing agent
   7. Thymectomy (uncommonly used)
5. Rituximab (Rituxan®) [11]
   1. Anti-CD20 monoclonal specific for B lymphocytes
   2. Effective in 5 children with highly refractory AHA
   3. Depletion of B cells occurred within 2 weeks of therapy
   4. Reconstitution of normal B cell levels occurred 5-9 months after therapy stopped
   5. Azathioprine and cyclosporine discontinued in all patients
   6. Prednisone dose reduced substantially in all patients
   7. Effective in pre- and post-splenectomy patients
6. Transfusion
   1. Indicated for acute, severe hemolytic anemia
   2. For many patients, hematocrit (HCT) >22% is safe and transfusion is avoided
   3. For patients with heart disease, poor pulmonary reserve, HCT 26-28% is usually desired
   4. Transfusion presents special problem here due to anti-RBC antibodies
   5. Increased risk for severe transfusion (hemolytic) reaction in these patients
   6. Premedication with diphenhydramine, acetaminophen, and glucocorticoids is common
   7. Very careful short-term followup is necessary
   8. Patients requiring a transfusion generally benefit from other modes of therapy
7. Polymerized bovine hemoglobin has been used effectively under compassionate guidelines [10]

References

1. Winkelstein A and Kiss JE. 1997. JAMA. 278(22):1982
2. Gutman JD, Kotton CN, Kratz A. 2003. NEJM. 349(12):1168 (Case Record)
3. Hemolysis from Ceftriaxone. Med Let. 44(1144):100
4. Barnett CF, Hsue PY, Machado RF. 2008. JAMA. 299(3):324
5. Vaughan JI, Manning M, Warwick RM, et al. 1998. NEJM. 338(12):798
6. Lo YMD, Hjelm NM, Fidler C, et al. 1998. NEJM. 339(24):1734
7. Kokori SIG, Ioannidis JPA, Voulgarelis M, et al. 2000. Am J Med. 108(3):198
8. Oliff IA and Compton CC. 2000. NEJM. 342(10):722 (Case Record)
9. Provan D and Weatherall D. 2000. Lancet. 355(9211):1260
10. Mullon J, Giacoppe G, Clagett C, et al. 2000. NEJM. 342(22):1638
11. Quartier P, Brethon B, Philippet P, et al. 2001. Lancet. 358(9292):1511
12. Gladwin MT, Sachdev V, Jison ML, et al. 2004. NEJM. 350(9):886
13. Bain BJ. 2005. NEJM. 353(5):498