Anemia: immune mediated hemolytic

Introduction

• Cause : may be primary immune-mediated or secondary, eg drugs, infections, lymphoproliferative disease. Common cause of regenerative anemia .
• Cause : antibodies (IgG or IgM) or complement bound to erythrocyte → intravascular or extravascular hemolysis.
• Signs : lethargy, tachypnea, tachycardia.
• Diagnosis : hematology, Coombs' test.
• Treatment : cytotoxic drugs : azathioprine, cyclosporine, prednisone.
• Prognosis : fair for chronic cases, 50% mortality for acute cases.

Diagnosis

Clinical signs

• Pallor.

• Pyrexia.

• Lymphadenopathy.
• Jaundice (acute disease).
• Hemoglobinuria (acute disease).
• Hepatosplenomegaly.

• Petechial hemorrhages, hematomas due to disseminated intravascular coagulopathy.
• Dyspnea due to pulmonary thromboembolism.

Diagnosis

Differential diagnosis

• Due to ruptured splenic tumor, especially hemangiosarcoma .
• Due to gastrointestinal bleeding.
• Due to urinary tract bleeding ( → urine analysis).
• Intra-cavitatory bleeding due to hemostatic disorder .

• Anemia of renal failure .
• Anemia of chronic inflammation (anemia not severe) . Anemia is mild; PCV>30%.
• Anemia of hepatic disease (anemia not as severe as for immune-mediated hemolytic anemia)
• Anemia associated with hypothyroidism , hypoadrenocorticism .

• Drug/toxic damage to bone marrow, eg estrogen .
• Lymphoid leukemia .
• Anemia associated with hemorrhage.

• Myeloproliferative disease /leukemia .
• Pure red cell aplasia .
• Anemia associated wtih iron deficiency.
• Hereditary hemolytic anemia, eg pyruvate kinase deficiency in Basenjies , phosphofructokinase deficiency /leukemia .

Sequelae

Prognosis

• Fair.

• Guarded to poor, mortality 50% plus.

Expected response to treatment

• Should see increase in PCV by 2-3% following 3-4 days of treatment, then a gradual increase over following 4-6 weeks. PCV may stay in low 30's → acceptable response to treatment. Animals with acute disease, especially with frank slide agglutination, may not respond and require aggressive treatment early on.

Reasons for treatment failure

• Acute disease may be refractory.
• Disseminated intravascular coagulopathy. Relapses may occur.

Sources

Publications

Refereed papers

• Recent references from PubMed.
• Weinkle T K, Center S A, Randolph J F, Barr S C & Erb H N (2005) Evaluation of prognostic factors, survival rates, and treatment protocols for immune-mediated hemolytic anemia in dogs: 151 cases (1993-2002). JAVMA 226 (11), 1869-1880 PubMed.
• Mcmanus P M & Craig L E (2001) Correlation between leukocytosis and necropsy findings in dogs with immune-mediated hemolytic anemia - 34 cases (1994-1999). JAVMA 218 , 1308-1313.
• Scott-Moncrieff, Treadwell N G et al(2001) Haemostatic abnormalities in dogs with primary immune-mediated hemolytic anemia. JAAHA 37 , 220-227.
• Stewart F E & Feldman B F (1993) Immune-mediated hemolytic anemia. Part II. Clinical entity, diagnosis and treatment theory. Comp Cont Ed Pract Vet 15 , 1479-1489. (Good review of causes and treatment.)

Other sources of information

• Raskin R E (2010) Haematologic Disorder. In: Clinical Medicine of the Dog and Cat.2nd edn. Schaer M (ed), Manson Publishing Ltd, London, pp 227-233.