Platelet Disorders Flashcards
How do you differentiate a thrombocytopenia of production vs destruction?
In destruction, you will see few platelets overall and the ones you do see will be large, as young platelets tend to be much larger.
Platelets are recycled in. . .
. . . the spleen
___ is generally associated with severe thrombocytopenia and may be a harbinger of complications such as gastrointestinal bleeding or even brain hemorrhage.
Mucosal purpura is generally associated with severe thrombocytopenia and may be a harbinger of complications such as gastrointestinal bleeding or even brain hemorrhage.
Platelet disorders table
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Primary hemostasis defects cause ___.
Secondary hemostasis defects cause ___.
Primary hemostasis defects cause superficial bleeding, petechiae, ecchymoses.
Secondary hemostasis defects cause deep bleeding, hematoma, hemarthralgia.
Decreased production of platelets differential
- Aplasia
- BM invasion
- Drugs/toxins
- TPO deficiency
Increased destuction of platelets differential
- Immune thrombocytopenia
- TTP
- HUS
- DIC
- Spleen hyperplasia (sequestration)
- Thrombosis (sequestration)
Most individuals with immune thrombocytopenia present to a hospital with ___.
Most individuals with immune thrombocytopenia present to a hospital with immune thrombocytopenic purpura.
In the majority of ITP patients, symptoms. . .
. . . resolve within 6 months, even without therapy
Presentation of ITP in children and young adulst
Typically present in younger individuals that are otherwise healthy with the sudden appearance of petechiae or ecchymoses a few days or weeks after an infectious illness, which is usually viral in nature
Why is it tough to detect antibodies on platelets?
Platelets have Fc receptors! They are going to have tons of antibodies on them and most won’t be pathologic
Presentation of ITP in adults
Adults with ITP have a strikingly different clinical presentation and course. In these patients, the onset is insidious and seldom accompanied by a viral prodrome. The illness is chronic and, when severe, requires meticulous and often complex management. In both children and adults, if ITP is the primary diagnosis, patients normally have no symptoms or physical findings except for purpura.
No lymphadenopathy, often menorrhagia in women, rarely cerebral hemorrhage.
Most common ITP antigen
GPIIb/IIIa
How might your treatment recommendation for ITP differ for a 26 yo professional hockey player vs. a 14 yo whose main hobbies were photography and reading vs. a 45 yo patient who was HIV positive?
26 yo: Splenectomy or corticosteroids
14 yo: Observation
45 yo: TPO mimetic or IVIG
Bone marrow biopsy of ITP
Increased megakaryocytes
Unlike autoimmune hemoltyic anemia, ITP is not associated with ___.
Unlike autoimmune hemoltyic anemia, ITP is not associated with fever and cytokine shock.
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Marrow biopsy of ITP
Increased megakaryocytes
The sudden development of purpura in an asymptomatic patient in whom the hemoglobin level, white blood cell count, and differential count are all normal is very likely to be __.
The sudden development of purpura in an asymptomatic patient in whom the hemoglobin level, white blood cell count, and differential count are all normal is very likely to be ITP.
Wet bleeding in ITP indicates ___ treatment.
Wet bleeding in ITP indicates corticosteroid treatment.
Drug-induced ITP
Either the drug haptenizes platelet antigens, or modifies antibody affinity to recognize platelet antigens
Treatments for ITP
- Observation
- Steroids
- Rituximab
- IVIG
- Splenectomy
- TPO-mimetics
- Antifibrinolytics (to prevent mucocutaneous wet bleeding)
- Anti-D (anti-Rh, old treatment, not used so much anymore, complication is possible hemoltyic anemia)
Based on this blood smear and a history of being stable but having fever and diffuse purpura, what is the likely diagnosis?
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Thrombotic thrombocytopenic purpura
Based on this blood smear and a history of being severely unstable, in hypotensive shock, and having diffuse purpura, what is the likely diagnosis?
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Disseminated intravascular coagulation
Five TTP characteristics
- Thrombocytopenia
- Microangiopathic hemolysis
- Fever
- Renal functional impairment
- Neurologic dysfunction
Hemoltyic uremic syndrome
Young children and elderly adults may develop acute microangiopathic hemolysis and thrombocytopenia accompanied by oliguria, proteinuria, and uremia, often following a diarrheal illness. 50% of cases caused by Shiga-toxin or Shiga-like toxins.
Most common cause of acute renal failure in young children.
TTP vs HUS
In patients with HUS, the anemia and thrombocytopenia are less pronounced than in those with TTP, and neurologic complications are rarely encountered, but the renal impairment is more severe.
Atypical HUS
Atypical = nondiarrheal
Commonly have an inherited mutation in one of six proteins that are either core components or regulators of the complement cascade: factor H, CD46, factor I, C3, factor B, and thrombomodulin.
All of these pathogenic mutations lead to complement hyperactivity, which is proposed to produce endothelial damage and localized thrombus formation, particularly within the small vessels of the kidney.
Those with atypical HUS often respond to treatment with eculizumab, an antibody directed against C5 that inhibits the terminal complement cascade.
C.O. is an 18 year old female college student with a history of menorrhagia, epistaxis, and easy bruising. She has been in generally excellent health and is currently on no medication except for iron supplements. For the past three years she has experienced nose bleeds, sometimes as often as once per week, without apparent cause. On several occasions, the bleeding was severe enough to require treatment in the E.D. where she received nasal packing. Other family members have a cluster of similar bleeding symptoms. Her platelet count is normal.
What is the likely diagnosis?
von Willebrand’s disease
Interference with primary hemostasis in the absence of thrombocytopenia
Likely want to treat with desmopressin and plasma-derived combined vWF-Factor VIII.
What is the problem with regular desmopressin?
Eventually the endothelial cells will run out of vWF, so you need to supplement with vWF enriched injections, like plasma-derived vWF-Factor VIII complexes.
To avoid this alltogether, you could try antifibrinolytics.
Aspirin-poisoned platelets
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Patients should not take ___ prior to surgery.
Patients should not take any anticoagulants, including aspirin and other NSAIDs prior to surgery.
While patients with myeloproliferative neoplasms usually have elevated platelet counts, they too often have . . .
While patients with myeloproliferative neoplasms usually have elevated platelet counts, they too often have prolonged bleeding times.
These patients are highly prone to developing either bleeding or thrombosis. Platelet aggregation studies are frequently abnormal in these patients, but the results have not been helpful in predicting either bleeding or thrombosis.
Glanzmann thrombasthenia
Inheritance of a defect in the gene for either GPIIb or GPIIIa. As a result, their platelets lack docking sites for fibrinogen binding.
Even though agonists such as adenosine diphosphate, arachidonic acid, epinephrine, and collagen can activate their platelets, aggregation fails to occur due to the absence of fibrinogen cross-linking. However, ristocetin still works in these patients to trigger aggregation, as this is mediated by vWF. (Opposite of Bernard-Soulier syndrome)
Bernard-Soulier syndrome
Defective GPIb/IX due to mutations in the gene encoding this receptor.
Their platelets aggregate normally in response to adenosine diphosphate, arachidonic acid, epinephrine, and collagen but do not aggregate or agglutinate in the presence of ristocetin. (Opposite of Glanzmann thrombasthenia)
Storage pool defect
Lack of ‘second wave’ aggregation due to either lack of or inefficient release of alpha and dense granules.
This phenotype may also be induced by aspirin.