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
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)
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
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
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
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
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