ISSN 2398-2969      

Anemia: immune mediated hemolytic

icanis

Synonym(s): AIHA, Immune-mediated hemolytic anemia, IMHA


Introduction

  • May be primary immune-mediated or secondary, eg drugs, infections, lymphoproliferative disease. Common cause of regenerative anemia Anemia: overview.
  • 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 Chemotherapy: general principles : azathioprine, cyclosporine, prednisone.
  • Prognosis: fair for chronic cases, 50% mortality for acute cases.

Pathogenesis

Etiology

Primary AIHA

  • Cause not known.
  • ?Genetic influences in certain breeds.

Secondary AIHA

Predisposing factors

General

  • Breed predispositions.

Specific

  • ?Increased incidence in following estrus in female.
  • Increased incidence in month following vaccination - suggested but not proven.

Pathophysiology

  • Auto-antibodies to red cell membrane components → removal of red cells from circulation → anemia.
  • Antibodies on red cells prompt the mononuclear phagocyte system to remove the red cells mainly in the spleen and liver, ie extravascular hemolysis → acute or chronic form of disease; chronic form more common.
  • Partially phagocytosed cells become spherocytes.
  • If antibodies fix complement on the red cell surface in sufficient quantities, intravascular hemolysis results → acute form of disease.
  • Increased red cell breakdown results in hyperbilirubinemia.
  • Hyperbilirubinemia → jaundice if bilirubin formation exceeds ability of liver to remove and conjugate it. Jaundice common with intravascular hemolysis, rare with extravascular hemolysis.
  • Cold hemagglutin disease → antibodies preferentially bind to red blood cells in blood colder than normal body temperatures, eg in peripheral capillary beds in cold weather. Agglutination → occlusion of capillary beds → ischemic necrosis.

Timecourse

  • Acute form 1-4 days.
  • Chronic form days to weeks.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Swann J W, Garden O A, Fellman C L (2019) ACVIM consensus statement on the treatment of immune-mediated hemolytic anemia in dogs. JVIM DOI: 10.1111/jvim.15463 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 (8), 1308-1313 PubMed.
  • Scott-Moncrieff, Treadwell N G et al (2001) Haemostatic abnormalities in dogs with primary immune-mediated hemolytic anemia. JAAHA 37 (3), 220-227 VetMedResource.
  • 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) AGRIS FAO.

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.

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