Hemo mehlman 4th Flashcards
Hemophilia A and B are …
XR
If you get a difficult vignette where you’re not sure of the Dx, just remember you’ll never see ……. in girls
hemophilia A and B (XR)
Skewed X-inactivation is called….
lyonization
don’t read between the lines: unless the vignette specifically makes the Q about skewed X-inactivation, any XR disorder will always be only in a boy.
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vWD is …
AD
vWD. In vignette what patient?
So you’ll often get a vignette with a girl.
USMLE will “reward” you sometimes with difficult vignettes. That is, if it’s a girl, you can instantaneously eliminate hemophilia.
vWD is always a mix of a ….. problem.
vWD is always a mix of a platelet and a clotting factor problem.
vWD platelet problem? CP
Platelet problem = epistaxis, petechiae, bruising; usually cutaneous
vWD clotting factor problem problem?
Clotting factor problem = excessive bleeding after tooth extraction; menorrhagia (heavy periods)
So vWD vignette you will get, e.g., epistaxis + heavy periods; or petechiae + lots of bleeding after tooth extraction; always a combo of the two
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Platelet problem = increased …
increased bleeding time (BT); bleeding time has zero relation to clotting factors / clotting
PT / aPTT = reflects clotting factors
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In vWD, bleeding time 100% of the time is elevated.
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vWF bridges ….. on platelets to ….
vWF bridges Gp1b on platelets to underlying collagen / vascular endothelium;
vWF is necessary for …
necessary for platelet adhesion
vWF does not affect …
does not affect aggregation (GpIIb/IIIa)
vWF also has ancillary/secondary function of……
But vWF also has ancillary/secondary function of stabilizing factor VIII in plasma, meaning sometimes aPTT is elevated (normal is 25-40 SECONDS).
1st important factor vWF: BT is always increased. aPTT is only elevated about half the time in questions.
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2nd important factor vWF: If aPTT is increased, it’s not absurdly increased. Iow, normal aPTT might be 42 seconds. And if it is normal, it might be upper end of normal, like 38 seconds, which can still suggest to you it’s vWD.
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vWD, what PT?
PT is always normal in vWD.
Normal BT = 2-7 minutes.
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Normal PT = 10-15 seconds
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Normal aPTT = 25-40 seconds
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