Monday, December 24, 2007

Merry Christmas

A 14 year old boy presents to your clinic with a swollen and painful left knee. He said it was preceded by stiffness and followed by a warm sensation, then acute pain. There is no history of trauma; the boy just played a basketball game. You send off labs and get a normal platelet count and PT, and a prolonged aPTT. A mixing test corrects the abnormality. You send off a specific factor VIII assay; it's normal.

Challenge: What's the next most likely diagnosis? This disease has another name; who was it named after? What is its transmission?

Related Questions:
1. What's the differential for a normal PT and a prolonged aPTT?
2. (Review) A normal aPTT and a prolonged PT?
3. (Review) A prolonged PT and aPTT?


Alex said...

PTT covers 12 11 9 8 (10 5 2). PT covers 7 (10 5 2). So a high PTT / normal PT means 12 11 9 or 8 are abnormal. In all likelihood, it is Hemophilia A (8). Around this time of the year though, Hemophilia B is more common, hence its associated name. If you see a long BT as well, it could also be Von Willibrand's Disease.

A high PT / normal PTT means 7 is abnormal. It's best to think of Factor 7-related vitamins like Vit K def or Vit E tox. Such is the case with an alcoholic with liver cirrhosis, a victim of rat poison, or a newborn with no bacteria in the gut.

If both are high, either 10 5 or 2 are abnormal, or more than one factor is deficient. The latter is true for DIC or Warfarin / Heparin use. It's a common misconception that PT is specific to warfarin and PTT to heparin; but both Pt and PTT are actually affected though the pairings allow more accurate dose evaluation.

There are other weird diseases and tests to figure them out. If adding normal plasma doesn't correct the PT/PTT, maybe they have an antibody against the coagulants. D-Dimers are helpful in checking DIC. Signs like hemarthroses and late rebleeding also give clues to the disease.

Craig said...

Merry Christmas

Hemarthrosis, bleeding into the joints, is characteristic of hemophilia. The inheritance is X-linked recessive. With normal factor VIII levels, this is most likely hemophilia B (deficiency in factor IX), also called Christmas’ disease after the first patient identified with it.

The differential for a normal PT and prolonged aPTT includes deficiency or inhibitors to factors VIII, IX, XI or XII; deficiency of prekallikrein or HMW kininogen; von Willebrand disease (vWD); heparin; and lupus anticoagulant. Lupus anticoagulant presents with thrombosis rather than bleeding; vWD presents with a mucosal platelet-suggestive bleeding diathesis; deficiency of VII, prekallikrein, and HMW kininogen do not present with a bleeding diathesis. The differential for a prolonged PT, normal aPTT include factor VII deficiency or inhibitor, vitamin K deficiency, liver disease, and coumadin. The differential for prolonged PT and aPTT include deficiency or inhibitor to prothrombin, fibrinogen, factor V, or factor X; combined factor deficiencies; liver disease; DIC; heparin; or coumadin.

Sources: UpToDate; Wikipedia.
haha nice job