Platelets Disorders Flashcards
What are the causes of platelets disorders ?
Thrombocytopenia
Defective platelets- acquired (common) or inherited (rare)
Thrombocytosis
What are the manifestations related to thrombocytopenia?
Purpura- Cutaneous bleeding
Petechiae- pinpoint skin bleeding
Mucosal bleeding- epistaxis, ecchymosis
Bleeding worsened by platelet inhibitor drugs such as aspirin, NSAIDs
What are the causes of thrombocytopenia ?
Artifactual- platelets clumping,satellites
Decreased production
Platelet loss (blood loss)
Increased destruction states (ITP,TTP,DIC)
Splenic sequestration
What are some common drugs causing thrombocytopenia ?
Ampicillin
Digoxin
Acetaminophen
What is Immune thrombocytopenia purpura (ITP)?
Abnormal antibody production coating platelets and causing accelerated destruction
Causes are idiopathic, collagen vascular diseases, lymphoma
Can be acute or chronic
What are the characteristics of acute ITP?
Last less than 6 months Childhood illness (2-6 years) Self limited in most cases
What are the characteristics of chronic ITP?
Last longer than 12 months
Adult illness
Require intervention
Affects more females than males
What are the lab findings in ITP?
Thrombocytopenia
Increased MPV
Increased size and number of megakaryocytes on bone marrow
What is the suggested lab testing in ITP?
HIV screening
Hepatitic C assay
ANA assay
How is ITP treated?
Treat for platelets less than 20,000 or dangerous bleeding
Steroids with Rituximab
Refractory therapy: splenectomy, danazol, immunosuppression
What are the outcomes from therapy for ITP?
Initial response rates of 66-75%
Initial duration is months or years
Most patients eventually relapse
Consequent therapy has lessened response
What is thrombotic thrombocytopenic purpura (TTP)?
Thrombotic microangiopathy caused by deficiency of VWF cleaving protein ADAMTS13
Results in thrombocytopenia, microangiopathic hemolytic anemia and widespread multi organ thrombosis and injury
What is hemolytic uremic syndrome (HUS)?
Triad of non Immune microangiopathic hemolytic anemia,thrombocytopenia and acute renal failure
Highly associated with infectious toxins (STEC O157 H7)
What are the symptoms of TTP and HUS?
Fever Anemia Thrombocytopenia Renal disease Neurologic symptoms Fever and neurologic symptoms are absent in HUS
What are the lab findings in TTP/HUS?
Thrombocytopenia with increased bleeding time
Normal PT/PTT
Anemia with schistocytes
Increased megakaryocytes in the bone marrow
How is TTP/HUS treated?
Plasmapheresis
Corticosteroids
What is heparin induced thrombocytopenia (HIT)?
Acquired hyper coagulable state arising from induction of an antibody against the heparin platelet factor 4 site
Onset is 4-10 days after heparin exposure
Very common
2 types: 1- minor clinical event, 2- white clot syndrome
What are the clinical manifestations of HIT?
Arterial thrombosis concurrent with venous thrombosis
Caused by heparin or LMW
How is HIT diagnosed?
50% or greater reduction in baseline platelet count, even if still in the normal range
Positive assay for heparin associated antibody
What are the factors that affect HIT scoring?
Thrombocytopenia
Timing of platelet count fall
Thrombosis or other sequelae
Other causes for thrombocytopenia
How is HIT treated?
Stop heparin in any dose, route or form
Anticoagulate with argatroban, lepirudin
Do not initiate coumadin
Avoid platelet transfusion
What is post transfusion purpura?
Acquired thrombocytopenia of the allo immune type
Typically occurs 5-15 days after transfusion of RBCs induces an alloantibody against the P1 antigen
Recipient is usually P1 negative, female and multiparous
It is usually severe (<10,000 platelets)
Patient often febrile
How is post transfusion purpura treated?
High dose gamma globulin
Plasmapheresis
Steroids
What is abnormal pooling of platelets?
AKA splenic sequestration
Occurs with diseases causing splenic enlargement and subsequent pooling
Usually part of pancytopenia
Therapy is dependent on the cause of the splenomegaly
What are the qualitative platelets disorders?
Glanzmann’s thrombastenia- absence of IIb/IIIa receptor: platelets can’t stick together
Bernard- Soulier- absence of Ib/V receptor: can’t bind to VWF
Von Willebrand’s disease- lots of bleeding, patient typically female, elevated PTT
What are the platelets level for surgical clearance in thrombocytopenia ?
Minor surgery safe if platelets >50,000
Vascular ans neurosurgical procedures require higher and sustained values
Dental procedures safe when>50,000
