Platelet disorders Flashcards
Bernard soulier clinical/lab features
- Mild to moderate thrombocytopenia
- large platelets
- highly variable bleeding phenotype (mild to severe)
Bernard soulier diagnosis - 1) response to ristocetin 2) response to adenosine and epinephrine
- platelet aggregometry.
- BSS platelets do not agglutinate or aggregate in response to ristocetin
- Prolonged with epinephrine
- normal to adenosine
Bernard soulier management 1) non life threatening bleeding 2) critical bleeding
IF non life threatening bleeding, plt transfusion to goal 30k + antifibrinolytics
Critical bleeding - recombinant factor VIIa
Steps of platelet aggregation
3 A’s
1) Adhesion -adhesion to damaged epithelium. Adhere to collagen, Regulated by Gp1A2A, GP4, GP6
2) Activation ( release contents of alpha and dense granules)
3) Aggregation
Receptor that mediates platelet aggregation
GP2B3A receptor, and through fibrinogen
2 types of platelet granules and contents
- alpha granules contain platelet factor 4, beta thromboglobulin, VWF, fibrinogen, Factor V, VIII, HMWK, albumin,
- dense granules - ATP, ADP, calcium, serotonin, magnesium
PFA negative predictive value
- very high (very good test of all steps of platelet function), essentially rules out platelet function defect
Bernard soulier inheritance pattern
- autosomal recessive
1) Bernard soulier mechanism 2) complex that is deficient
- *abnormal aggregation to ristocetin
- lack of Gp1b/IX complex
General treatment of platelet disorders during acute bleeding episode
- recombinant factor 7
What to be cautious about with platelet transfusion in bernard soulier
alloimmunization (antibodies to Gp1b)
1) grey platelet syndrome mechanism 2) name of gene mutation
- lack of alpha granules secondary NBEAL2 gene mutation
grey platelet syndrome findings on periphearl smear
- large platelets
- platelets appear grey with poo granularity due to lack of alpha granules
**see photo online
grey platelet syndrome sequela to know
- predisposed to myelofibrosis
hermansky pudlak inheritance
autosomal recessive
hermansky pudlak demographics
Puerto rican (pocket of cases)
1) hermansky pudlak mechanism 2) name of gene mutation
Lack of dense granules, defect in HPS1 gene (hermansky pudlak)
hermansky pudlak and platelet studies
- lack of second wave with ADP and epinephrine
- dense granules or decreased on immunofluorescense
hermansky pudlak clinical features
- pulmonary fibrosis
- albinism
- colitis
- neurologic changes (nystagmus)
Quebec platelet disorder inheritance pattern
Autosomal dominant (so multiple family members affected)
Quebec platelet disorder mechanism
- Decrease in alpha granule protein leading to abnormal aggregation w/ epinephrine
- increased urokinase plasminogen (confirm)
Chediak higashi mechanism
- mutation in LYST gene (lysosomal trafficking regulator protein)
*platelet storage defect
Chediak higashi labs
*thrombocytopenia
anemia
neutropenia
Chediak higashi bone marrow biopsy finding
myeloperoxidase inclusion in neutrophils
Chediak higashi clinical features
- immunodeficiences
Chediak higashi treatment
- steroids
- splenectomy
- prophylactic antibiotics
- consideration for transplant
1) glanzman’s thrombasthenia mechanism 2) response to ristocetin
- platelet aggregation defect, abnormal aggregation to collagen and ADP
- *lack of GPIIbIIIa receptor
- no primary wave seen
-
normal aggregation to ristocetin
(opposite to bernard soulier so important to remember)
*GLANZMANN’s = GLOBAL (lack of response to all with exception of ristocetin)
glanzman’s thrombasenia inheritance pattern
autosomal recessive
Management of bleeding in glanzman’s thrombasenia
recombinant factor 7
congenital afibrinogenemia lab features
- prolonged PT + PTT
Wiskott aldrich mechanism
WASP gene mutation
Wiskott aldrich smear
- small platelets
Wiskott aldrich clinical features
- ezcema
- ## frequent infections
Wiskott aldrich inheritance pattern
- x linked recessive (thus more common in males)
MYH9-RD inheritance pattern
autosomal dominant
MYH9-RD lab features
- large platelets
- dohle bodies in neutrophils (see photo of smear online)
MYH9-RD clinical features
- cataracts
- hearing loss
- renal disease
Bernard soulier labs
- large platelets
- mild thrombocytopenia
What do alpha granules contain?
- VWF
- Fibrinogen
- PF4
- Growth factors: PDGF/TGF-Beta1
- Factor V
What do dense granules contain?
- ADP/ATP
- serotonin
- calcium
1) How do you look at dense granules? 2) platelet disorders with dense granule defects
Electron microscopy (far smaller than alpha granules you can see with light microscopy)
- need for Hermansky-Pudlak, Chediak-Higashi, Delta-storage pool disorders
Utility of PFA
- it’s a useful screening test
- BUT has low sensitivity for platelet defects and can’t differentiate platelet disorders from VWD
What is the gold standard for platelet function?
Platelet aggregometry
What does platelet aggregometry curve show?
- See photo on desktop
*some labs x axis is flipped
Glanzmann’s thrombasthenia on platelet aggreggation
- absent aggregation to almost all antagonists (ADP, collagen, epinephrine) (think Glanzmann’s = global), only to ristocetin
(Lack of GP11a/IIIb receptor leads to no binding of fibrinogen)
What will you see on platelet aggregometry with Bernard-Soulier?
- normal to ADP, collagen, epinephrine but flat curves/no response to ristocetin (lack of Ib/V/IX receptor complex leads to no binding of VWF)
What does TEG look at?
determines interaction of fibrin, platelets, proteins in coagulation cascade using whole blood
Next step if TEG looks like a test tube
Give platelets
Next step if TEG looks like an upside down martini glass
Give TXA
Next step if TEG looks like a champagne flute
Give cryo
If photo shows electron microscopy, what should you be thinking?
dense granule problem
For what platelet defects is flow cytometry useful for?
(surface GpIb, IX, Ia, IIa, IIb, IIIa - Bernard-Soulier, Glanzmann’s, Wiskott-Aldrich, collagen receptor defects)
Alpha and delta storage pool defects
Hermansky Pudlak result on platelet aggregation
- lack of secondary wave with ADP
Bernard SOulier result on platelet aggregation
- absent aggregation to ristocetin
Other clinical clues to grey platelet syndrome
- myelofibrosis
- splenomegaly
- moderate thrombocytopenia (though not all pts)
Other clinical features of MYH9-RD
- hearing loss
- renal disease
- cataracts
What are the storage pool diseases?
- Hermansky Pudlak
- Chediak HIgashi
- Grey platelet syndrome
- Quebec platelet syndrome
Grey platelet syndrome inheritance pattern
- autosomal recessive
Platelet aggregometry result with all the storage pool defects
lack of secondary wave to epinephrine (secondary wave driven by release of granule contents)
RUNX1 related platelet disorder clinical features
- variable thrombocytopenia
- variable platelet dysfunction
- AML risk
Platelet disorder with highest risk of developing specific anti-platelet antibodies
Glanzmann’s thrombosthenia
General treatment of platelet defect disorders
- plt transfusion
- antifibrinolytics
- DDAVP
- recombinant Factor VIIa
Uremic platelet dysfunction management
- dialysis
- DDAVp
*cryo
What are the P2Y12 antagonists?
- ticlopidinie
- clopidogrel
- prasugrel
Clopidogrel associated with what condition?
TTP
What are the IIB/IIIa inhibitors associated with?
Drug-induced thrombocytopenia (tirofiban and eptifibatide)
Pathophys of MYH9-related disorder
- defect of cytoplasmic structure and cell mobility due to mutation in nonmuscle myosin heavy chain IIA
Qualitative platelet syndromes associated with mild thrombocytopenia
- grey platelet syndrome
- Bernard soulier
Platelet size in Glanzmann’s
Normal