Block 3 PATH Exam -- Platelet Disorders (#23)

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Breakdown of platelet distrubtion in body: 2/3 circulate
1/3 are stored in the spleen
What is the lifespan of platelets?: 7 - 10 days
What is epistaxis?: Nose bleed
Name 6 manifestations of PRIMARY hemostatic defects: Superficial purpura
Petechiae
Epistaxis
Mucous membrane bleeding
Prolonged IMMEDIATE bleeding

"Oozy bruisy" patient
How does thromboxane effect platelet aggregation? What is the role of NSAIDs?: Thromboxane mediates expression of Gp IIb/IIIa on platelets

NSAIDs inhibit Thromboxane formation from arachidonic acid
What is a normal platelet count (range)?: 150 - 450 k
Ranges of different classifications of thrombocytopenia (Mild, moderate, etc.) (corresponding #s of platelets): Mild - 80-120 k
Moderate - 50-80 k
Vigilant - 30-50 k
Worry - 20-30 k
Crisis - 10-20 k

PANIC - <10 k
Charactertistics of Wiskott-Aldrich Syndrome: X-linked inheritance

Small platelets

Assoc. w/ immunodeficiency, eczema
Characteristics of familial thrombocytopenia w/ AML: Dominant inheritance

Normal size/dysfunctional platelets

Propensity to develop AML
Amegakaryocytic thrombocytopenia w/ radio-ulnar synostosis What are its main characteristics?: Dominant inheritance

Assoc. w/ hearing loss
Charecteristics of thrombocytopenia w/ absent radii (TAR)?: Recessive inheritance

Skeletal defect - absent radius
Characteristics of Bernard Soulier thrombocytopenia: Autosomal recessive

Large, dysfunctional platelets

Deficiency of GP 1b receptor on platelets
Characteristics of DiGeorge thrombyctopenia: Palate T-cell defect

Large platelets

Right heart problems
Characteristics of vWD 2B: Dominant inheritance

Platelet clumping on smear

Due to vWF structural defect
Benign Mediterranean Macrothrombocytopenia What type of inheritance does it have?: Dominant
Characteristics of MYH9-related thrombocytopenia: Dominant inheritance

Giant platelets
Neutrophil inclusions

+/- hearing loss, cataract, renal defect
Characteristics of Gray platelet syndrome: Dominant inheritance

Large, pale platelets

LACK of alpha granules
Characteristics of Amegakaryocytic thrombocytopenia (CAMT): Recessive inheritance

Possible stem cell defect
Congenital thrombocytopenias w/ autosomal recessive inheritance (3): CAMT
TAR
Bernard Soulier
What is deficient/defective in Glanzmann's thrombastenia?: Gp IIb/IIIa
What two "factors" are required for Adhesion?: von Willebrand factor
Gp Ib
How do adhesion and aggregation differ in energy requirements?: Adhesion - NON-energy requiring

Aggregation - energy requiring
What drugs are assoc. w/ drug-induced thrombocytopenia (6): Quinidine
Heparin
NSAIDs
Gold salts
Sulfa drugs
Dilantin
How are WBCs affected in ITP?: They're not
Normal number & morphology
What main change is visible in the BM of ITP?: Increased megakaryocytes
How do acute and chronic ITP compare in terms of age group of pts?: Acute - PRE-adolescent

Chronic - POST-adolescent
How do acute and chronic ITP compare in terms of sex predilection?: Acute - F:M equal

Chronic - F:M is 3:1
Which type of ITP is more often associated w/ infection?: Acute
How do acute and chronic ITP compare in terms of typical platelet counts?: Acute - < 20k

Chronic - 20-80k
How do acute and chronic ITP compare in terms of duration?: Acute - 2-6 weeks

Chronic - years
How do acute and chronic ITP compare in terms of resolution?: Acute - often resolves

Chronic - w/o treatment, resolution unusual
Above what platelet count does risk of bleeding drop below 5%?: > 10k
How do you treat ITP w/ a platelet ct < 20k?: Steroids, IVIg, anti-D

NOTE: anti-D is given to Rh- pts. who may receive Rh+ blood
How do you treat Asymptomatic ITP w/ platelet ct 20-30k?: Prednisone
How do you treat SYMPTOMATIC ITP w/ platelet ct 20-30k?: Treat as if platelets < 20k
How do you treat Asymptomatic ITP w/ platelet ct 30-100k?: Do nothing
How do you treat ITP w/ platelet ct 30-100k if minor bleeding?: Prednisone
How do you treat ITP w/ platelet ct 30-100k if major bleeding?: Treat as if platelets < 20k
When is relapse of ITP likely if treated w/ splenectomy?: In first 6 months
What are the 3 modalities of drug-induced thrombocytopenia?: Immune complex deposition (common)

Hapten "penicillin" type

Auto-sensitization of platelets
What drug is often associated w/ auto-sensitization of platelets?: Aldomet (methyldopa)
What are the major differences between HITT Type 1 and 2 (4)?: ---Type 1---
Non-immune, CAN continue heparin, Occurs early, No sequelae

---Type 2---
Immune rxn, Must STOP heparin, Occurs later, DISASTER
What type of Ab is induced in HITT Type 2? What is it targeted against?: IgG

Heparin-PF4 complex on platelets
What is the typical pentad of signs in TTP?: Low platelet count
Fever
Renal failure
Neuro deficits
Microangiopathic hemolytic anemia
(strands of fibrin acoross small vessels)
What causes congenital TTP?: Lack of ADAMSTS13 enzyme
(vWF multimers are not cut, causing clumping of platelets)
How is TTP treated? If not treated, what is the mortality?: Plasma exchange
(remove Abs and replace ADAMSTS13)

90% fatality
What is HUS assoc. w/? (causative factor): E. Coli toxin
How does the renal failure in HUS compare w/ that in TTP?: It is much more pronounced in HUS
What symptoms does TTP commonly have that is not seen in HUS? (differentiating factor?): Neuro deficits
Mnemonic for pregnancy associated hemolysis/thrombocytopenia: HELLP

Hemolysis
Elevated
Liver enzymes
Low
Platelets
Aggregation requires what two "factors" from platelets?: Presence of and ability to release granules
Ability to form Gp IIb/IIIa receptor
What is the function of the Gp IIb/IIIa receptor?: Binds fibrinogen
Thus, fibrinogen can link platelets

Required for AGGREGATION
What is the function of the Gp Ib receptor?: Binds sub-endothelial vWF
Thus, platelets can adhere to vessel wall

Required for ADHESION
Pooled platelet concentrate transfusion How many units per donor?: Each unit is from an individual donor

SO, if 6 units, 6 donors
Pheresis unit How many units per donor?: 6-8 units come from a single donor
How long are platelets viable at room temp?: ~5 days
What "normal" physiological processes can cause thrombocytosis (2)?: Exercise
Peri-partum state

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