Platelet disorders DSA Flashcards
thrombocytopenia- caused by 2 conditions
- dec prod of platelets
- inc destruction/sequestration of platelets
thrombocytosis caused by 2 conditions
- overprod of platelets (essential thrombocythemia)
- inc platelet released from marrow/storage areas in response to an infl stimulus (reactive thrombocytosis)
Decreased platelet production
- bone marrow failure
- bone marrow infiltration
- chemotherapy and irradiation
- nutritional deficiencies
- cyclic thrombocytopenia
Thrombocytopenia due to bone marrow failure
- congenital- fanconi anemia, Wiskott-aldrich syndrome
- acquired- aplastic anemia, MDS
Increased platelet destruction
- immune thrombocytopenia
- thrombotic microangiopathy
- HIT
- DIC
Immune thrombocytopenia- essentials of diagnosis
- isolated thrombocytopenia
- asses for any new causative medications and HIV and Hep C infections
- dx of exclusion
ITP- treatment
- corticosteroids with IVIG or WinRho (anti-D)
- platelet transfusions can be given if active bleeding is present
- anti-B cell ab rituximab
- splenectomy
Thrombotic microangiopathy
- TTP and HUS
- thrombocytopenia due to incorporation of platelets into thrombi and microangiopathic hemolytic anemia (shearing of erythrocytes in fibrin networks)
TTP
-autoab’s against ADAMTS-13- accum of vWF multimers- aggregate platelets
HUS
- classic- caused by E coli (shiga toxin)
- atypical- leads to acute kidney injury- defects in proteins that reg complement activity
thrombotic microangiopathy- pentad of sx’s
-microangiopathic hemolytic anemia, thrombocytopenia, fever, kidney disease, neuro system abnormalities
thrombotic microangiopathy- tx
-plasma exchange- mortality rate is 95% w/o tx
Heparin induced thrombocytopenia
-IgG ab’s to heparin-platelet factor 4 complexes- activates platelets- leads to thrombocytopenia and a pro-thrombotic state
HIT- essentials of dx
- thrombocytopenia within 5-14 days of exposure to heparin
- decline in baseline platelet count of 50% or greater
- thrombosis occurs in up to 50% of cases; bleeding is uncommon
DIC- essentials of dx
- frequent cause of thrombocytopenia in hospitalized pts
- prolonged activated partial thromboplastin time and prothrombin time
- thrombocytopenia and dec fibrinogen levels
Other conditions causing thrombocytopenia
- drug-induced
- posttransfusion purpura
- von willebrand dz type 2B
- platelet sequestration
- pregnancy
- infection or sepsis
- pseudothrombocytopenia
posttransfusion purpura
- sudden onset thrombocytopenia in a pt who had received transfusion of red ces, platelets, or plasma within 1 wk
- ab’s against the human platelet antigen PlA1
- either multiparous women or persons who have received transfusions previously
- admin of IVIG
platelet sequestration
-splenomegaly may lead to thrombocytopenia
pregnancy
-expansion of the blood volume- leads to hemodilution
Qualitative platelet disorders
- Bernard-Soulier Syndrome
- Glanzmann thrombasthenia
- storage pool diseases
- acquired- medications
Congenital disorders of platelet fxn- essentials of dx
- usually dx in childhood
- FH usually positive
- may be diagnosed in adulthood when there is excessive bleeding
Bernard-Soulier syndrome
- rare, autosomal recessive
- reduced or abnormal platelet memb expression of glycoprotein Ib/IX (vWF R)
Glanzmann thrombasthenia
- abnormality in glycoprotein IIb/IIIa R’s on the platelet membrane, which are required to bind fibrinogen and vWF, both which bridge platelets during aggregation
- autosomal recessive
storage pool disease
-defects in the release of alpha or dense platelet granules
activated platelets release the contents of plt granules to reinforce the aggregatory response normally
Bernard-Soulier syndrome- lab findings
- abnormally large platelets, moderate thrombocytopenia, prolonged bleeding time
- plt aggregation studies show a defect in response to ristocetin (response to other agonists is normal)
- dx confirmed by platelet flow cytometry
Glanzmann thrombasthenia- lab findings
-platelet aggregation studies show marked impairment of aggregation in response to stimulation with typical agonists
storage pool disease- lab findings
- gray platelet syndrome- defects in alpha granules, thrombocytopenia, and marrow fibrosis
- albinism-associated- defective dense granules
- non-albinism-associated- seen in Ehlers-Danlos, Wiskott-Aldrich syndrome
Qualitative platelet disorders- tx
-transfusion of normal platelets
Essential Thrombocytosis- essentials of dx
- elevated platelet count in absence of other causes
- normal red blood cell mass
- absence of BCR/ABL gene
Essential Thrombocytosis- path
- prolif of megakaryocytes in the bone marrow
- JAK2 mutations
Essential Thrombocytosis- sx and signs
- 50-60 yo
- most common clinical problem- thrombosis
- erythromelalgia- painful burning of hands
Essential Thrombocytosis- lab findings
-elevated plt count- hallmark
Essential Thrombocytosis- must be distinguished from?
secondary causes of an elevated plt count!
- reactive thrombocytosis- plt count seldom exceeds 1,000,000
- infl disorders and chronic infection can cause elevations in platelet count
Essential Thrombocytosis- tx
oral hydroxurea
