ITP Flashcards

1
Q

Idiopathic thrombocytopenic purpura (ITP)

A
  • Autoimmune disorder characterized by thrombocytopenia and induced by autoAbs against various platelet membrane receptors
  • The opsonized platelets will be destroyed via phagocytosis by macrophages
  • The Abs can also attack megakaryocytes in the BM, but this is less damaging
  • There’s usually either normal or even slightly elevated megakaryocytic # in BM (due to decreased platelets)
  • ITP is a form of increased destruction, but is also accompanied w/ ineffective production
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2
Q

Types of ITP

A
  • Can be acute or chronic
  • Acute: duration of 6 mo or less (commonly in children), rapid onset usually following a viral illness, usually self-limiting
  • Chronic: longer than 6 mo (commonly in adults), slow onset with no preceding viral infection and rare spontaneous remission (platelet counts may remain at 1/3rd of normal)
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3
Q

Dx of ITP

A
  • Propensity for bleeding
  • Exclusion of other disorders that can cause thrombocytopenia (leukemia, aplastic anemia, BM disorders like myelodysplasia, infection)
  • Hx and PE, CBC, blood smear should be used (look for family Hx of thrombocytopenia)
  • Cutaneous manifestations of ITP include mucocutaneous petechiae, ecchymoses, and purpura
  • Large platelets (young) in blood smear
  • Absence of hepatosplenomegaly and lymphadenomegaly
  • Response to ITP Rx: IVIg, anti-D Ig, steroids
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4
Q

Pathophysiology of ITP

A
  • GPIIb/IIIa and GPIb/IX are major targets for autoAbs (both on megakaryocytes and platelets)
  • ITP involves: platelet destruction (both T and B cell mediated) and decreased production (due to Abs and CTLs attacking megakaryocytes)
  • CTLs (CD8 Ts) are directed against platelets and megs, and CD4s are needed to induce B cell targeting of platelet Ags
  • Patients w/ ITP are at increased risk of bleeding including from GI and intracranial
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5
Q

Rx strategies

A
  • Increase platelet count to prevent bleeding
  • Minimize Rx-related toxicity
  • Preserve patient activity
  • Who you treat w/ what depends on the extent of the thrombocytopenia and past Hx
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6
Q

Rx’s of ITP

A
  • Initial Rx w/ corticosteroids (prednisone), which increases vascular integrity and platelet survival (due to decreased production of Abs against platelets), and decreased clearance of Ab coated platelets
  • Can use repeated high-dose dexamethasone
  • IVIg are used for those unresponsive to corticosteroids or w/ critical bleeding
  • IVIg can rapidly increase platelet count (as can IV anti-D Ig)
  • IVIg down-regulates Fc receptor expression, inhibits complement binding, and interferes w/ opsonization of Abs to platelets
  • Splenectomy is an option, which will remove the site of phagocytosis of the platelets
  • Can also use TPO agonists, anti-CD20 Ig to kill B cells and up regulate Tregs
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7
Q

ITP vs TTP

A
  • In TTP you see schistocytes due fragmentation hemolytic anemia (high bili/LDH, decreased BT and platelet count)
  • Due to ADAMTS13 deficiency
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