A 47-Year-Old Woman Comes to the Office Due to Knee

question 287

Multiple Choice

A 47-year-old woman comes to the office due to knee pain.  The patient slipped on an icy step 2 weeks ago and fell on her knee.  Since that time, she has had severe knee pain and a large overlying bruise, which has failed to heal.  The patient underwent a Roux-en-Y gastric bypass 6 months ago for morbid obesity and has lost 20 kg (44.1 lb) since then.  She does not use tobacco or alcohol.  Vital signs are normal.  On examination, a large ecchymosis is present over the left knee.  The knee is swollen, painful to palpation, and has a limited range of motion.  There are several smaller ecchymoses and petechiae located on all four extremities.  Laboratory results are as follows: Left knee x-ray reveals a large effusion but no fracture.  Arthrocentesis yields brown fluid positive for xanthochromia.  Which of the following best explains this patient's manifestations?

• A)Acquired factor VIII inhibitor
• B)Acquired platelet dysfunction
• C)Small vessel vasculitis
• D)Vitamin C deficiency

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Definitions:

Energy Of Activation

The minimum energy that must be supplied to reactants to initiate a chemical reaction.

Amino Acids

Organic compounds that serve as the building blocks for proteins, containing both amine and carboxyl functional groups.

Proteins

Large, complex molecules made up of amino acids that play critical roles in the body, including in structures, enzymes, and immune responses.

Enzyme-reactant Interaction

The specific process by which an enzyme binds to a reactant, or substrate, to catalyze a biochemical reaction.