A 64-year-old man comes to the emergency department due to acute knee pain. He developed redness, swelling, and severe pain affecting the right knee the day before his arrival. The patient has had 3 similar episodes in the past year that resolved quickly with over-the-counter analgesics. He has a history of polycythemia vera but has been noncompliant with phlebotomy treatments. Vital signs and cardiopulmonary examinations are normal. The right knee is red and warm. There is severe pain with movement at the joint; the other joints are grossly normal. Needle aspiration of the joint is performed. Which of the following is the most likely finding on analysis of this patient's synovial fluid?

Question

A 64-year-old man comes to the emergency department due to acute knee pain.  He developed redness, swelling, and severe pain affecting the right knee the day before his arrival.  The patient has had 3 similar episodes in the past year that resolved quickly with over-the-counter analgesics.  He has a history of polycythemia vera but has been noncompliant with phlebotomy treatments.  Vital signs and cardiopulmonary examinations are normal.  The right knee is red and warm.  There is severe pain with movement at the joint; the other joints are grossly normal.  Needle aspiration of the joint is performed.  Which of the following is the most likely finding on analysis of this patient's synovial fluid?

Quizplus · Accepted Answer

11ec160b_3b63_f2e6_9249_4dda3a8a38fa_MD0001_00 This patient, with recurrent acute monoarthritis and history of a myeloproliferative disorder, has typical features of gout. Gout occurs when there is an increased uric acid concentration in serum and synovial fluid, leading to monosodium urate crystal formation and deposition in synovium and cartilage. Gout is most common in joints where cooler temperatures favor crystal formation, especially in the distal lower extremity (eg, first metatarsophalangeal joint, ankle, knee). Uptake of urate crystals by neutrophils leads to free radical release, cytokine production, and joint inflammation. The hyperuricemia that predisposes to gout can be idiopathic (primary gout) or due to increased urate production (eg, myeloproliferative disorders) or decreased urate clearance by the kidneys. Gouty arthritis presents with acute onset of severe joint pain, warmth, erythema, and swelling. The diagnosis is established by synovial fluid analysis, which shows increased white blood cells. Monosodium urate crystals are seen under polarized light microscopy and may be present both intra- and extracellularly. They are characteristically needle-shaped and negatively birefringent (when the crystals are aligned parallel to the slow ray of the compensator, they appear yellow; when aligned perpendicular, they appear blue). (Choice A) Osteoarthritis causes chronic, progressive arthritis in the distal hands and weight-bearing joints. Synovial fluid analysis shows normal to minimal inflammatory findings. (Choices B and C) Gonococcal arthritis presents with fever, skin lesions, and inflammatory mono- or oligoarthritis. Staphylococcal septic arthritis causes a fulminant monoarthritis, usually with fever. Recurrent episodes are more characteristic of gout. (Choice D) Rheumatoid arthritis causes a chronic polyarthritis, typically involving the metacarpophalangeal joints of the hands. Synovial fluid will show a sterile inflammatory effusion. (Choice F) Nontraumatic hemarthrosis is most commonly seen in patients taking anticoagulants (eg, warfarin) or with bleeding disorders (eg, hemophilia). (Choice G) Crystal arthritis due to calcium pyrophosphate deposition (pseudogout) most commonly affects the knee and is often similar to gout. However, it is less common and not associated with myeloproliferative disorders. Educational objective: Gout results from the deposition of monosodium urate crystals in the joints and soft tissues. Under polarized light, urate crystals appear needle-shaped and negatively birefringent. Conditions that increase uric acid production or decrease uric acid clearance can increase the risk of gout. __________ References: Hyperuricemia, gout, and related comorbidities: cause and effect on a two-way street. (http://www.ncbi.nlm.nih.gov/pubmed/24937517)

A 64-Year-Old Man Comes to the Emergency Department Due to Acute