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Biochem. and Medical Genetics
BGEN 3020
Jason Leboe- Mcgowan

Chapter 10 Fibrinolytic system: Plasmin Plasmin – leaves crumbs – its breaks down things (fibrinogen, fibrin, coagulation factors) – think fibrinoLYTIC system. When it breaks down a clot, there are many pieces (ie fibrin) left around, which are fibrin degradation products. What is the single best screening test for DIC? D-dimers (better answer) or fibrin split products. What plasmin does is breaks things apart, leaving crumbs behind and you have degradation products. D dimers are the absolute best test for DIC (di- means 2). When you form a fibrin clot, factor 13 (fibrin stabilizing factor) makes the clot stronger. How do you stabilize strands? Link them by putting connections between them to make them stronger (this is what factor 13 does). So, how do you make collagen stronger? By, linking them to increase the tensile strength (factor 13 will put a crossbridge in fibrin). What D-dimer is detecting are only those fibrin factors that have a link (ie when there are two of them held together, this what the test picks up). What does this absolutely prove? That there is a fibrin clot. Do you see this in DIC? Yes. Example: Would you see it if you broke apart a platelet thrombus in a coronary artery? (Remember a platelet thrombus is a bunch of platelets held together by fibrin). So, what would the D dimer assay be if you broke apart that clot? Increased, you would see increased D dimers and would see the little fibrin strands held together by cross linking. They often do that to see if you have recanalized or if you got rid of your thrombus. Example: it is often also seen with a pulmonary embolus, b/c if you have a pulmonary embolus, one test is a D dimer b/c you will form a clot that will activate the fibrinolytic system, and it will try to start breaking it down, and there will be a release of D dimers. Single best test for DIC. Good test for picking up pulmonary embolus, along with ventilation/perfusion scans. Excellent test to see if you have reperfusion after given t-PA b/c it proves that if D dimers were present, a fibrin clot must be present (fibrin was there so it proves it). Vessel abnormalities Senile purpura: Seen on the back of hands of an old person – they hit things and get senile purpura; vessels get unstable as you get older and subcutaneous tissue thins. When you hit yourself, BV’s rupture and you get echymoses – called senile purpura, an age dependent finding. Only present in places that normally hit things, back of the hands and the shins. Example: Mom was put in old age home and the children were gonna sue the old age home for abuse. Do the children have a case? No, b/c it has nothing to do with abuse and is an age dependent finding. Example: now if they also saw echymoses on buttocks and back, this is not a normal place to get trauma related to just bumping into things – that would be abuse. Senile purpura is the cause of echymoses on the back of the elderly’s hand. Everyone will get this, everyone, no one is exempt. Osler Weber Rendu Dz aka hereditary telangiectasias: Many of these pts have chronic Fe def anemia, related to persistent GI bleeds. You can make the dx with PE of the pt. The pt will have small red dots called telangiectasias and if you look on the lips and tongue you will see telangiectasias, and if you do endoscopy, you will see the little red dots thro
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