Ma- Platelet Lecture 8-23-06
Terms
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- What is TTP etiology?
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Sporadic caases are due to an antibody against the protease which cleaves the ultra-large molecular wt multimers of von Willebrand's factor.
The protease is called ADAMTS-13, which stands for A Disintegrin And Metalloprotease with Thrombospondin like repeats... more - treatment for TTP?
- plasma exchange
- should platelet transfusion be used for ttp tx?
- no- they fuel the fire
- what are the unique features of TTP/HUS?
- fever, neuro sequelae, but more renal manifestiations. usually precipitated by dirrheal illness. esp e.coli 0157:H7 or shigella . more in ped pts. respond less well to plasma exchange
- what drugs are clinically induce thromocytomenia?
- B-lactam antibiotics, Trimethoprim-sulfamethoxazole and other sulfa drugs, quinine/quinidine, heparin, abciximab (ReoPro)
- what is heparin induced thrombocytopenia?
- 1-3% of pts with heparin get it 7-10 days after heparin, platelts fall by 30-50%. plattlet counts do not have to be normal. if platelets fall on heparin, stop heparin immediately. can lead, paradoxically to thrombosis in some pts.
- ITP?
- need to exclude splenomegaly and subclinical thyroid disease. megakaryocytes should be present inthe marrow because it is a peripheral descructive process. in adults when platelt count < 50, get tx.
- ITP in kids?
- in kids is is usually provoked by viral illness and no tx needed.
- itp tx?
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corticosteriods, take 48-72 hrs to take effect.
if platelet count <10K, or if pt bleeding, need more rapid Tx, use IVIg
if pt is Rh +, cuse Anti-D in place of IVIg, acts as a decoy for splenic macrophages - ITP Therapy?
- 2/3 of adult pts will relapse after steriod taper. in this case, splenectomy is required. 2/3 of pts respond to splenectomy. otherwise, more immunosuppresson
- splenic sequestration?
- normally 1/3 of total platelet mass resides in spleen. splenic enlargement from any cause can lead to displacement of platelets from peripheral circulaton into splenic pool.
- splenimegaly causes?
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Portal Hypertension
Malignancy
Chronic Hemolytic Diseases-Hemoglobin C (not Sickle Cell Disease, they have small spleen!), Thallassemias, Hereditary Sperocytosis. - Thrombocytosis?
- too many platelets!