Autoimmune Hemolytic Anemia (AIHA) - Part 2

Definition: Warm autoantibodies are those that primarily react at 37 degrees Celsius, making up about 70% of autoimmune hemolytic anemias, particularly in transfusion medicine.
Characteristics of Warm Autoimmune Hemolytic Anemia:
- Most frequent cause of autoimmune hemolytic anemia.
- Antibodies involved are typically IgG.
- Extravascular hemolysis occurs as macrophages phagocytize red blood cells (RBCs) coated with IgG.
- Common site of destruction is the spleen.

Rh Testing: Warm autoantibodies can interfere with Rh typing; hence, an Rh control is necessary.
Antibody Screens and Identifications: It complicates the interpretation of antibody screens and antibody identifications (IDs).
Direct Antiglobulin Test (DAT): Used when there are positive antibody screens that raise uncertainties in diagnosis.
Auto Control: Confirms the presence of an autoantibody by testing the patient’s cells against their own serum.
Warm Auto Absorption Procedure:
- A process that treats the patient’s red cells to remove autoantibodies.
- The treated red cells are used to absorb the autoantibodies to identify any alloantibody.

Signs and Symptoms:
- Similar to symptoms of other types of anemia including:
- Pallor: pale skin.
- Weakness.
- Dizziness.
- Dyspnea: difficulty or labored breathing.
- Jaundice.
- Unexplained Fever.
- Most patients exhibit severe anemia, often requiring blood transfusions.

Prevalence: More frequently observed in adults.
Idiopathic Cases: No identifiable underlying disease in some patients.
Associated Causes:
- Infection.
- Trauma.
- Surgery.
- Pregnancy.
Underlying Diseases Associated:
- Hodgkin's disease.
- Lupus: most commonly encountered, particularly in females.
- Rheumatoid Arthritis.
- Gastrointestinal Diseases: such as ulcerative colitis.

Reticulocyte Count: Increased due to the body’s compensation for RBC loss.
Bilirubin Levels: Increased levels of unconjugated (indirect) bilirubin are noted.
Urobilinogen: Increased levels.
Haptoglobin: Decreased levels due to scavenging of lysed RBCs.
Positive DAT: Indicates the presence of either complement and/or IgG (rarely just complement).
Antibody Screen, Antibody ID, Auto Control: All tests will generally yield positive results due to IgG or complement.
Peripheral Blood Smear:
- Features include:
- Polychromasia: correlates with increased reticulocyte count.
- Macrocytosis.
- Nucleated Red Cells: presence signifies bone marrow urgency to compensate for RBC loss.
- Spherocytosis: a result of immune response coating RBCs with antibodies.
LDH Levels: Increased, but this test is non-specific.
Negative Donath-Landsteiner test: Essential to distinguish from other conditions.

Underlying Disease Management: Treat any associated underlying disease, if identifiable.
Cardiovascular Support: Especially crucial for severely anemic patients.
Corticosteroids:
- Prednisone is often used to reduce clearance of antibody-coated RBCs and suppress the immune response.
- High initial doses help stabilize hematocrit levels and reduce autoantibody production.
IVIG (Intravenous Immunoglobulin): Administered if patients do not respond adequately to steroids.
Splenectomy: Considered beneficial for idiopathic cases or when corticosteroid therapy fails.
Immunosuppressive Drugs:
- Last resort options include Rituximab, Imuran, and Cyclophosphamide.
- These treatments have significant side effects such as increased infection risk and infertility.
- Rituximab specifically targets antibody-producing B-cells.
- Risk factors include kidney damage from Cyclosporine.

Challenges: Finding compatible blood is often difficult, especially since warm autoantibodies frequently target common antigens (e.g., little e).
Transfusion Protocols:
- Rh negative blood must be managed cautiously, often challenging due to common antigenicity against antibodies.
- In cases where blood needs to be administered, clinicians may provide the least incompatible blood only if necessary, despite reservations.

Characteristics:
- Presence of both warm and cold autoantibodies.
- Laboratory results indicate both types' activity.
- Often seen alongside acute hemolysis leading to transfusion needs.
- May be idiopathic or tied to conditions like lymphoproliferative disorders, lupus, or infections like HIV.
Laboratory Analysis for Mixed Type: Positive DAT for both IgG and complement.
Treatment Typically: Includes the use of corticosteroids.

Types: Described in three types:
- Type I - Haptin-dependent antibody: Drug binds membrane proteins, inducing antibody responses (e.g., Penicillin).
- Type II - Autoantibody: Induced autoantibodies specific to red cell membranes (e.g., Methyldopa). Recovery follows discontinuation.
- Type III - Drug-dependent antibody: Antibody binds red cells only when the drug is present; this is theoretical with unclear mechanisms.
Common Drugs Associated:
- Antimicrobials, NSAIDs, diuretics, Cefotetan, Ceftriaxone.
Management: Discontinue the offending drug immediately; usually leads to recovery without special treatment.
Monitoring: Critical for hemoglobin and hematocrit levels.

Recognizing autoimmune hemolytic anemias, specifically warm autoantibodies and drug-induced types, is imperative for timely and appropriate management, promoting patient recovery and mitigating complications.