Platelets Abnormalities Flashcards
What are the clinical findings in patients with either thrombocytopenia or platelets dysfunction ?
Petechiae
Ecchymoses
Epistaxis
Menorrhagia
What are the general classes of platelets disorders?
Thrombocytopenia
Thrombocytosis
Defective function
What are the causes of thrombocytopenia ?
Decreased production
Decreased survival
Sequestration
Dilution
What are the causes of thrombocytosis ?
Reactive
Neoplastic
What are the causes of defective function ?
Defective adhesion Defective aggregation Defective secretion Liver disease Uremia Drug effect
What are the inherited platelets abnormalities ?
May-Hegglin anomaly Bernard-Soulier syndrome Thrombocytopenia with absent radii Wiskot-Aldrich syndrome Glanzman thrombasthenia
What are the characteristics of May-Hegglin anomaly?
Autosomal dominant Large platelets Dohle bodies in leukocytes Normal platelet function Patient not prone to bleeding
What are the characteristics ofBernard-Soulier syndrome?
Autosomal recessive
Bleeding is due to defective adhesion of platelets to subendothelial collagen after vascular injury
Secondary to deficiency of GPIb complex
Platelets aggregate with all agonists except on ristocetin
What are the characteristics with absent radii (TWAR or TAR)?
Autosomal recessive maybe Thrombocytopenia with normal platelet morphology but abnormal function Decreased megakaryocytes Absent radii, normal thumbs Presentation at birth
What are the characteristics Wiskott-Aldrich syndrome?
X-linked recessive
Variable expression, often with IgM deficiency
Thrombocytopenia with small platelets
Decreased platelet survival
What are the characteristics of Glanzman thrombasthenia?
Autosomal recessive
Bleeding due to defective platelet aggregation caused by deficient GPIIb/IIIa
Normal platelet count and morphology
Only react to ristocetin
What is primary immune thrombocytopenic purpura?
Mild to severe bleeding disorder Severe thrombocytopenia Can be acute or chronic Normal physical examination other than signs of mucocutaneous hemorrhage No hepatosplenomegaly
What are the characteristics of secondary immune thrombocytopenic purpura ?
Indistinguishable from primary
Occurs in the setting of systemic autoimmune disease
Greater tendency to remain chronic or recur
Diagnosis of either kind is by exclusion
What are the characteristics of RBC fragmentation syndromes with thrombocytopenia?
Mechanical destruction of circulating RBCs with formation of schistocytes
What are the causes of RBC fragmentation syndromes with thrombocytopenia ?
Disseminated intravascular coagulation (DIC)
Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS)
Mechanical heart valves
What are the DIC common causes?
Obstetric complications Infections of all types Intravascular hemolysis Snake bites Leads to consumptive coagulopathy and bleeding diathesis
What are the lab findings of DIC?
PT, PTT, TT usually prolonged Fibrinogen decreased Thrombocytopenia D-dimer, FDP are elevated Schistocytes usually seen on peripheral smear
What are the characteristics of TTP/HUS?
Destructive thrombocytopenia and diffuse microvascular occlusion by platelet( not fibrin) thrombi
Due to endothelial damage and excessive platelet clumping
Coagulation tests are usually normal
What is the clinical features of TTP?
Severe thrombocytopenia
Microangiopathic hemolytic anemia
Neurologic dysfunction
Fever
What are the diagnostic features to suggest TTP?
Schistocytosis Thrombocytopenia Increased LDH Definitive testing for ADAMTS-13 May not be available at time of diagnosis, should treat emergently based on clinical signs/symptoms and above findings
How to treat TTP?
Emergent plasma apheresis
Do not treat with platelets
What are the characteristics of HUS?
Microangiopathic hemolytic anemia
Acute renal failure
Thrombocytopenia
Prodrome of bloody diarrhea, abdominal pain, nausea and vomiting
Treatment is dialysis and supportive therapy
No association with ADAMTS-13
What are the 2 main types of HUS?
Primary- rare, due to complement gene mutations and antibodies to complement
Secondary- most common, due to infection (Shiga toxin, HIV), drug toxicity
What is the most common STEC- associated HUS?
Common mode is contaminated hamburger
What are the 2 types of heparin induced thrombocytopenia (HIT)?
Type 1: non immune- occurs rapidly after heparin administration, caused by direct platelet aggregating effect of heparin
Type 2: immune- occurs within 5-14 dayss after beginning heparin caused by antibodies to a complex of heparin and low molecular weight proteins
What is the most common cause of drug induced platelet dysfunction ?
Aspirin
Inhibits cyclooxygenase
Impairs platelet aggregation
No effects on coagulation cascade
