Clinical Pathology: Haematology

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Clinical Pathology Haematology

• Group D

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Scenario

• A 25 year old female presented with
• 2 week history of progressive tiredness and
  dyspnoea on exertion
• 3 week history of intermittent migratory
  arthralgia
• 2 years ago pleurisy
• no meds
• mucosal pallor with mild scleral icterus
• palpable spleen (3cm)
• normal joints
• urine negative for bilirubin and blood

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Scenario cont.

• moderate anisocytosis numerous spherocytes
• prominent polychromasia mild red cell
  agglutination
• nucleated red cells
• neutrophilia with occasional band forms

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Scenario cont.
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Scenario cont.

• Other results
• positive direct antiglobulin test (Coombs Test)
• IgG and complement demonstrated on the red cells
• Increased polychromasia i.e. elevated
  reticulocyte count, is strong evidence for
  haemorrhage or haemolysis, and either may be
  associated with neutrophilia and or
  thrombocytosis.
• Warm type autoimmune haemolytic anaemia is
  suspected.
• Investigation for other autoimmune disorders is
  carried out, with the history of arthralgia and
  pleurisy suggesting systemic lupus erythematous.

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Questions

• Explain the significance of the presence of
  spherocytes and mild red cell agglutination
• Explain the result of the Direct Antiglobulin
  (Coombs) test
• What medications and conditions are associated
  with warm type AIHA?
• What place does testing for antinuclear
  antibodies (ANA) and antidoublestranded DNA play
  in informing a diagnosis of SLE?

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• Warm type AIHA is associated with a
• number of conditions and medications
• explain ?

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• Classification of autoimmune haemolytic anaemia
• I. On the basis of serologic characteristics of
  involved autoimmune process
• A. Warm autoantibody type-autoantibody
  maximally active at body temperature, 37ºC
• B. Cold autoantibody type-autoantibody
  active at temperatures below 37ºC
• C. Mixed cold and warm autoantibodies
• II. On basis of presence or absence of underlying
  or significantly associated disorder
• A) Primary or idiopathic AIHA
• B) Secondary AIHA
• 1) Associated with lymphoproliferative
  disorders
• 2) Associated with rheumatic disorders,
  particularly systemic lupus erythematosus
• 3) Associated with certain infections
• 4) Associated with certain non-lymphoid
  neoplasms
• 5) Associated with certain chronic inflammatory
  diseases
• 6) Associated with ingestion of certain drugs

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Diseases associated with warm type AIHA
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Etiology and pathogenesis

• Malignancy associated AIHA the origin of
  pathologic antibodies is unknown
• Theories
• 1) Malignancies disrupt the normal immune
  function surveillance, that allows both
  autoantibodies to form and neoplasia to
  proliferate
• 2) malignant cells are the source of the anti
  erythrocyte antibody
• non-malignant disease often of immunologic
  origin, general immune system disturbance is the
  etiology
• Erythrocyte autoantibodies produced in these
  diseases cover RBCs ? complement system responds
  to these antibody coated cells causing RBC
  phagocytosis
• In general there is an inverse relationship
  between the quantity of red cell bound auto
  antibodies and red cell survival.

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Clinical Features and Management

• In secondary AIHA the haemolytic anaemia and
  associated features (weakness, fatigue, fever,
  bleeding and other symptoms and signs of anaemia)
  may be overshadowed by the more serious symptoms
  and signs of the underlying disease.
• Treatment of the secondary disease may also bring
  the AIHA under control, however in some
  situations the disease may need to be treated
  separately glucocorticoids or transfusion.

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Drug induced warm-type AIHA
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Autoantibodies

• In SLE, B cells spontaneously produce a large
  amount of immunoglobulins, including three types
  of autoantibodies
• nucleic acid binding proteins (histones and
  ribonucleoproteins)
• nucleic acids (DNA)
• cell membrane antigens (phospholipids)
• The different antibodies vary widely in their
  diagnostic and pathological significance

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Autoantibodies cont.
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Antinuclear autoantibodies

• Heterogeneous group
• Their presence is associated with a variety of
  diseases and disease manifestations, thus they
  are a non-specific marker of disease.
• Antinuclear antibodies are also detectable in
  individuals with no symptoms of autoimmune
  disease
• Many diseases presumed to be autoimmune in nature
  have no known association with antinuclear
  autoantibodies

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Anti-Ro autoantibodies

• The Ro antigen is a small intracellular complex
  between RNA and a membrane protein
• High anti-Ro titres in patients with SLE has been
  associated with lymphopenia and leukopenia,
  myocarditis and cardiac conduction defects

Anti-La autoantibodies

• The La protein has a molecular weight of about 50
  kDa and is involved in RNA polymerase III
  transcription
• The significance of its presence in patients with
  SLE is not fully understood

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Antiphospholipid autoantibodies

• Directed against negatively charged phospholipids
  including ß2 glycoprotein, phosphatidic acid,
  phosphatidylserine, cardiolipin and
  phosphatidylinositol
• The presence of antibodies against these
  phospholipids is significantly associated with
  arterial and/or venous thrombosis
• Anti-cardiolipin antibodies have been associated
  with abnormal intracardiac anatomy

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Anti-Sm autoantibodies

• The Smith antigen is a small uridine rich RNA
  molecule bound to a common group of core
  proteins, forming part of the complex that
  splices pre-mRNA
• Titres are usually constant

Anti-RNP autoantibodies

• RNP ribonucleoprotein
• High levels of anti-RNP may indicate potentially
  fatal features e.g. fibrosing alveolitis or
  polymyositis

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Anti-dsDNA autoantibodies

• In patients without SLE, binding is in a
  sequence-specific manner to linear epitopes
• In SLE, binding depends on ionic interactions and
  requires DNA flexibility
• Anti-dsDNA antibodies are 75-95 sensitive and
  95-99 specific for SLE
• A rising titre of anti-dsDNA often heralds the
  development of nephritis or vasculitis

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Anti-dsDNA autoantibodies cont.

• Autoantibodies bind with DNA or DNA-histone
  conjugates to form circulating immune complexes
• These complexes deposit in different tissues to
  elicit inflammation
• They may react with plasma membrane-associated
  antigens on different cells and stimulate release
  of mediators which amplify the inflammatory
  response

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References

• American College of Rheumatology ad hoc Committee
  on SLE Guidelines Guidelines for referral and
  management of systemic lupus erythematosus in
  adults. Arth Rheum 42(9)1785-96 1999
• Arbuckle MR. McClain MT. Rubertone MV. Scofield
  RH. Dennis GJ. James JA. Harley JB. Development
  of autoantibodies before the clinical onset of
  systemic lupus erythematosus. New Eng J Med
  349(16)1526-33, 2003
• Esdaile JM. Abrahamowicz M. Joseph L. MacKenzie
  T. Li Y. Danoff D. Laboratory tests as predictors
  of disease exacerbations in systemic lupus
  erythematosus. Arth Rheum 39(3)370-8, 1996 Mar
• Mok CC, Lau S. Pathogenesis of systemic lupus
  erythematosus. J Clin Path 56481-90 2003
• Ulvestad E, Kanestrem A, Madland TM, Thomassen E,
  Haga HJ, Vollset SE. Evaluation of Diagnostic
  Tests for Antinuclear Antibodies in
  Rheumatological Practice. Scand. J. Immunol.
  52309-15 2000
• Venables PJW. Fortnightly Review Diagnosis and
  Treatment of SLE. BMJ 307(6905)663-6 1993