Autoimmune Idiopathic Thrombocytopenic Purpura (ITP)

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Autoimmune Idiopathic Thrombocytopenic
Purpura(ITP)

• Nicola Davis

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ITP

• Clinical syndrome in which a decreased number of
  circulating platelets presents as a bleeding
  tendency, easy bruising, or extravasation of
  blood from capillaries into skin and mucous
  membranes

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• The thrombocytopenia seen in ITP is due to immune
  destruction of platelets.
• Abnormal antibody binds to circulating platelet
  membranes.
• The immunoglobulin coated platelets induce
  phagocytosis primarily in the spleen.
• Thrombocytopenia develops if the bone marrow is
  unable to increase production of platelets to
  compensate for the destruction.

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Acute ITP

• Usually seen in children
• Peak incidence 3 -5 years
• M F
• Usually occurs 2 weeks following a viral
  infection
• Often self limiting

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Chronic ITP

• Usually seen in adults
• Peak incidence 30 - 40 years
• Onset in patient gt60 years is uncommon
• FM 31
• US incidence 1/10,000 annually
• Usually idiopathic but may occur in association
  with other autoimmune disorders, in patients with
  CLL and after viral infections

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Clinical Features

• Easy bruising
• Purpura
• Epistaxis
• Menorrhagia
• Major haemorrhage is rare
• Splenomegaly is rare

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Investigations

• Diagnosis of exclusion
• FBC
• isolated thrombocytopenia
• anaemia or neutropenia may indicate other
  diseases - though may be iron deficiency anaemia
  from chronic blood loss in chronic ITP
• Blood Smear
• morphology of platelets is typically normal with
  varying numbers of large platelets
• morphology of RBCs and leukocytes should be
  normal

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• Bone Marrow
• normal or increased numbers of megakaryocytes
• otherwise normal
• Antiplatelet Antibodies
• if -ve does not rule out ITP
• not essential for the diagnosis of ITP

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Treatment

• In children
• Treatment depends on bleeding risk
• Platelets gt 30 can be managed without specific
  treatment
• Platelets lt 20 are given oral prednisone
  1mg/kg/day. May also be given high dose IV Ig
  causing a transient rise in platelet levels.

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Treatment

• In Adults
• Platelets gt 50 have a low risk of haemorrhage and
  no specific treatment is needed
• Platelets lt 30 are treated with oral prednisone
  1mg/kg/day. (Improvement seen in a few days)
• Platelets lt 5 are high risk and should be treated
  with methylprednisolone and Ig
• Platelet transfusions may be used to control
  bleeding acutely

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Surgical Options

• Splenectomy
• usually results in rapid, complete, lifelong
  remission in acute ITP
• 90 of chronic ITP respond following splenectomy,
  although 30 of these eventually relapse
• There is a lifelong risk of sepsis from
  encapsulated bacteria following splenectomy so
  will need immunisation against H. influenzae type
  B and S. Pneumoniae - boost every 5 years.

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Treatment-Resistant ITP

• In those patients who do not respond to
  corticosteriods or splenectomy immunosuppresive
  drugs may help
• azathioprine
• cyclophosphamide
• vincristine
• danazol a non-virilising androgen may also help
• anti-CD20 (rituximab)

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Prognosis

• Children
• gt80 with untreated ITP have spontaneous recovery
  in 2-8 weeks
• Treatment with prednisone and Ig accelerates the
  increase in platelet count decreasing the chance
  of serious haemorrhage

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Prognosis

• Adults
• 60 - 90 of adults have an increased platelet
  count after treatment with prednisone and Ig
• Of those who have a splenectomy 65 have a
  sustained response and 10 - 15 have a partial
  response

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Thank You