A 52-year-old man comes to the emergency department with a 24-hour history of pain and swelling of his right knee. He has no fevers, chills, or recent trauma to the knee. In addition, the patient has had constipation, excessive urination, and fatigue for the past several months. His medical history is notable for a kidney stone a year ago that passed with intravenous and oral hydration. The patient does not take any prescription medications, and does not use tobacco, alcohol, or illicit drugs. His temperature is 37.2 C (98.9 F) and blood pressure is 130/76 mm Hg. Examination shows tenderness, erythema, and swelling of the right knee. The remainder of the examination is unremarkable. Laboratory results are as follows: Arthrocentesis is performed. Which of the following is most likely to be found on synovial fluid assessment in this patient?

Question

A 52-year-old man comes to the emergency department with a 24-hour history of pain and swelling of his right knee.  He has no fevers, chills, or recent trauma to the knee.  In addition, the patient has had constipation, excessive urination, and fatigue for the past several months.  His medical history is notable for a kidney stone a year ago that passed with intravenous and oral hydration.  The patient does not take any prescription medications, and does not use tobacco, alcohol, or illicit drugs.  His temperature is 37.2 C (98.9 F) and blood pressure is 130/76 mm Hg.  Examination shows tenderness, erythema, and swelling of the right knee.  The remainder of the examination is unremarkable.  Laboratory results are as follows:  Arthrocentesis is performed.  Which of the following is most likely to be found on synovial fluid assessment in this patient?

Quizplus · Accepted Answer

11ec25c8_d518_501b_bc81_e1ab13911580_MD0003_00 This patient has symptomatic hypercalcemia (fatigue, constipation, nephrolithiasis [likely calcium stones]), suggesting primary hyperparathyroidism. He now has acute inflammatory arthritis. Pseudogout is caused by calcium pyrophosphate dihydrate (CPPD) crystals in the joint space and is a common complication of hyperparathyroidism with chronic hypercalcemia. Pseudogout is also associated with hypothyroidism and hemochromatosis. Pseudogout presents with acute pain, swelling, redness, and limited motion of the involved joint(s), with the knee most commonly affected. Synovial fluid analysis will show an inflammatory effusion. The rhomboid-shaped, positively birefringent crystals of CPPD can be difficult to detect on synovial fluid analysis but are diagnostic when present. X-ray can also be useful to diagnose pseudogout and typically reveals chondrocalcinosis. crystals chondrocalcinosis (Choice A) Clear, non-inflammatory joint fluid would be seen in osteoarthritis, which would usually cause chronic polyarticular pain rather than an acute monoarthritis with erythema and leukocytosis. (Choice B) Hemorrhagic joint fluid is usually seen in trauma (eg, anterior cruciate ligament tear), bleeding disorders (eg, hemophilia), or anticoagulant use. Atraumatic hemarthrosis is otherwise uncommon. (Choice C) Needle-shaped crystals with negative birefringence are diagnostic of gout. Gout can also cause renal stones (uric acid) and an acute painful monoarthritis of the knee, but is more common in the first metatarsophalangeal joints and is not associated with hypercalcemia. Needle-shaped crystals (Choice D) Polymorphonuclear cells with gram-positive cocci would indicate septic arthritis. Although septic arthritis typically presents with acute inflammatory arthritis, most patients have a recent or concurrent infection and likely have fever on presentation. This patient's hypercalcemia makes pseudogout more likely. Educational objective: Hyperparathyroidism with chronic hypercalcemia can cause pseudogout, presenting as acute, painful monoarthritis. Diagnostic findings include calcification of the articular cartilage (chondrocalcinosis) on x-ray and rhomboid-shaped, positively birefringent calcium pyrophosphate crystals in synovial fluid.

A 52-Year-Old Man Comes to the Emergency Department with a 24-Hour