Immune thrombocytopenic purpura

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Background

GENERAL

  1. low platelets and mucocutaneous bleeding
  2. half occur in kids
  3. either primary or secondary to other disorder
  4. either acute or chronic > 6mo
  5. usually presents days to weeks after infection
  6. in kids, 70% resolve in 6 mo regardless of tx or not
  7. adults usually chronic, insidous onset and more likely in women than men

PATHOPHYS

  1. mediated by autoantibodies- platelets coated with igg antibodies undergo accelerated clearance in spleen and liver
  2. can get compensatory increase in platelet production in some pts
  3. in other pts, get abnormal production destruction of intermedullary antibody coated platelets
  4. level of thrombopoietin not increased
  5. methods to tx are directed at 1- antibody prodctn, 2- platelet sensitization, 3- clearance, 4- production.

GENETICS

  1. can be seen in certain families and twins
  2. HLA type may predict response to different tx's
  3. no consistent assoc btwn HLA types and ITP however

Diagnosis

  1. is dx of exclusion
  2. can get secondary ITP in SLE, antiphospholid syn, immune deficiency states, leukemia, lymphoma, HIV, Hep C, heparin and quinidine.
  3. duration of bleeding tells acute from chronic
  4. absence of systemic symptoms helps rule out secondary forms and other dxs
  5. family hx usually negative.
  6. physical exam shows platelet type bleeding-petechia, purpura, conj hem,
  7. if spleen very big, consider other dx
  8. can see anemia if have lots of blood loss
  9. can see large young plateltets on perif smear
  10. bone marrow bx- debatetable- but need it if atypical case, fever, pain, neutropenia, unexplained macrocytosis.
  11. dx by measuring platelet assoc antibodies- fair sensitivity, specificity and predictive value
  12. neg test does not rule it out

Initial Management

ADULTS

  1. if plts above 50k- will dx incidentally
  2. plts 30k- 50k- will get easy bruising
  3. petechia and purpura at 1-k- 30k
  4. <10k at risk for internal bleeding
  5. adults usually require tx with prednsone at tme of presentation
  6. can also use Anti- D immune globulin in Rh + pt
  7. IV IG used for internal bleeding
  8. splenectomy within 3- 6mo if more than 10- 20 mg prednisone per day.

KIDS

  1. outcome so good usually dont need to tx unless risk of intracranial hem- plts <10k- 20k
  2. usually observe and avoid sports, ASA..
  3. if severe thrombocytopenia- can tx with IV IG or anti D IG. or prednisone.

Urgent Tx in Kids

  1. neuro sxs, internal bleeding, surgery- tx with iv solumedrol and iv ig and platelet infusion
  2. consider vincristine
  3. consider splenectomy
  4. plasmapharesis not helpful
  5. consider antifibrinolytic/ aminocaproic acid fo mucosal bleeding
  6. for severe bleeding- iv ig and iv platelets

Management of First Relapse

ADULTS

  1. no tx if asymptomatic with plt 30k
  2. splenectomy if relapse or not response to steroids, iv ig or iv anti D ig

KIDS

  1. delay splenectomy as long as possible- or if symptomatic > 1yr or severe thrombocytopenia

SPLENECTOMY

  1. immunize against H flu, pneumoccus, and give daily prophylactic penicilin for 1 yr

Chronic Refractory ITP

  1. 30- 40% adults do not respond to splenectomy or have relapse p splenectomy
  2. hunt for accessory splene
  3. tx with prednisone, iv ig
  4. next step is medicine that impedes platelet clearance- Danazol, Dapsone, vinca alkaloids.
  5. if splenectomized, do not give ig anti D ig.
  6. immunesuppression if platelet <20k and no response to above tx- use azathioprine or cyclophosphamide
  7. Azathioprine watch LFT's- is also carcinogenic
  8. Cyclophoshamide- marrow suppression, hem cystitis, bladder fibrosis, alopecia, infertility, leukemia and teratogenic.

Children

  1. azathioprine alone or in combination with cyclophosphamide.

Complications

  1. fatal bleeding from ICH- risk greatest in elderly or recurrent bleeding or no response to tx

Source

6/06 MISTRY