Wednesday, December 22, 2010
5:55 AM | Posted by Shams Burki | Edit Post
Hb 11.8 g/dL
WBC 6.9 × 109/L
Platelets 405 × 109/L
Bleeding time normal
Prothrombin time 13 s (normal range 11–15)
Activated partial thromboplastin time 60 s (control 25–34)
Factor VIII level 123 per cent
What is the diagnosis?
(a) Von Willebrand’s disease
(b) Factor VIII deﬁciency
(c) Factor V (Leiden) mutation
(d) Factor IX deﬁciency
(e) Protein C deﬁciency
A 6-year-old boy presents with a painful, red,swollen knee. There is no evidence of systemic infection but he has a prolonged APTT with normal factor VIII levels
Well I cant stress it more but know these disease in the clinical vignette for your USMLE.
The clinical history suggests a differential diagnosis of haemarthrosis or septic arthritis. However,the prolonged APTT make this a haemarthrosis.
The normal bleeding time and platelet level make this a defect of the clotting cascade, and the APTT and prothrombin time put it in the intrinsic pathway. The most common defect, factor VIII deﬁciency or haemophilia A, is excluded; the answer is the next most likely, factor IX deﬁciency or haemophilia B. The lack of a family history is of no signiﬁcance as one-third of patients carry new mutations.