Gout

GOUT 43A

A 58-year-old man with a long history of treated essential hypertension and mild renal insufficiency presents to the urgent care clinic complaining of pain in the right knee. His primary care provider saw him 1 week ago and added a thiazide diuretic to improve his blood pressure control. He had been well until the night before the clinic visit, when he noted some redness and slight swelling of his knee. He later awakened with significant pain and swelling. He was able to walk only with assistance. There was no history of knee trauma. Physical examination confirmed the presence of a swollen right knee, with erythema and warmth. Joint aspiration recovered copious dark yellow, cloudy synovial fluid. Microscopic analysis demonstrated 30,000 leukocytes/mcL; negative Gram stain results; and many needle-shaped, negatively birefringent crystals.

What are the salient features of this patient’s problem? How do you think through his problem?

Salient features: Chronic kidney disease; monoarticular joint pain, warmth and erythema; thiazide use; synovial fluid with white blood cell (WBC) count of 30,000/mcL, negative Gram stain, needle-shaped negatively birefringent (urate) crystals

How to think through: A septic joint is the first consideration in patient with monoarticular joint pain and inflammation (rubor [redness], dolor [pain], calor [warmth], tumor [swelling])—that is, a true arthritis. The other two major causes of monoarticular arthritis are trauma and crystal-induced arthropathies. Does the patient fit the demographic profile for gout? (Yes.) Is his joint one typically affected by gout? (Yes, most common are the great toe, midfoot, and knee.) What is the tempo of the onset of pain in gout? (Rapid escalation.) What are the risk factors for gout? (Thiazides, myeloproliferative disorders, alcohol intake.) Can patients with gout have fever? (Yes.) How does synovial fluid analysis help? (Both gout and infection can cause a WBC count >50,000/mcL. Although the joint fluid Gram stain and culture help to rule out infection, finding crystals establishes the diagnosis of gout definitively.) Where on the body you might find tophi? (Cartilage, external ears, hands, feet, olecranon and prepatellar bursae, tendons, and bone.) What might radiography show in gout? (Erosions.)