A 36-year-old man comes to the emergency department due to severe, acute knee pain that awoke him from sleep. He has a history of end-stage renal disease for which he underwent a renal transplant 8 weeks ago. The patient takes an immunosuppressive regimen that includes cyclosporine and low-dose prednisone. He visited his nephrologist last week and serum creatinine levels were normal with no proteinuria. Temperature is 37.5 C (99.5 F), blood pressure is 136/78 mm Hg, and pulse is 88/min. Examination shows redness, warmth, and a small effusion in the left knee. Passive range of motion at the knee causes severe pain. Microscopic examination of joint fluid from the knee shows numerous neutrophils as well as both intra- and extracellular crystals as shown in the exhibit.

Which of the following mechanisms is most likely responsible for this patient's acute symptoms?

Question

A 36-year-old man comes to the emergency department due to severe, acute knee pain that awoke him from sleep. He has a history of end-stage renal disease for which he underwent a renal transplant 8 weeks ago. The patient takes an immunosuppressive regimen that includes cyclosporine and low-dose prednisone. He visited his nephrologist last week and serum creatinine levels were normal with no proteinuria. Temperature is 37.5 C (99.5 F) , blood pressure is 136/78 mm Hg, and pulse is 88/min. Examination shows redness, warmth, and a small effusion in the left knee. Passive range of motion at the knee causes severe pain. Microscopic examination of joint fluid from the knee shows numerous neutrophils as well as both intra- and extracellular crystals as shown in the exhibit.

Which of the following mechanisms is most likely responsible for this patient's acute symptoms?

Quizplus · Accepted Answer

11ec160b_3c7e_3c6c_9249_df8c482676f7_MD0001_00 This patient has acute monoarticular arthritis of the knee with synovial fluid evidence of inflammation and needle-shaped (monosodium urate) crystals, indicating a diagnosis of gout. Gout develops in patients with hyperuricemia and is associated with several risk factors including excessive alcohol intake, meat/seafood consumption, chronic kidney disease, and certain medications. Cyclosporine is a common cause of gout exacerbations in patients who have undergone solid organ transplantation, particularly renal transplantation. This medication impairs renal excretion of uric acid, resulting in hyperuricemia. Although high doses of systemic glucocorticoids (eg, prednisone) can be used to treat acute gout, the low doses used for immunosuppression in patients who have undergone transplantation are usually not sufficient to prevent gout flares. (Choice B) Increased production of uric acid is commonly due to a purine-rich diet (eg, red meat, seafood), excessive alcohol intake, fructose-sweetened beverage intake, or disorders associated with increased cell turnover (eg, myeloproliferative disorders, cancers). (Choice C) Urate-lowering agents (eg, allopurinol) are used to prevent recurrent gout but can occasionally precipitate a gout flare due to rapid declines in blood uric acid levels, which can disrupt preexisting crystal deposits and increase their immunogenicity. This patient is not taking a medication that lowers uric acid levels. (Choice D) Patients who have malignancy associated with high tumor burdens (eg, acute lymphoblastic leukemia) can develop tumor lysis syndrome when cytotoxic chemotherapy is initiated. The massive release of nucleic acids into the circulation (from lysed cells) increases serum uric acid levels (due to catabolism of purine nucleic acids) and can precipitate gout. (Choice E) Diuretics (eg, furosemide, hydrochlorothiazide) can be associated with gout as these medications reduce urate excretion in the proximal tubule and also cause volume depletion leading to decreased renal perfusion and filtration of uric acid. This patient has a normal serum creatinine level, indicating adequate renal function. Educational objective: Patients undergoing solid organ transplantation are at increased risk of gout due to medications that impair renal clearance of uric acid. Cyclosporine is particularly associated with gout in the post-transplantation period due to decreased uric acid excretion.

A 36-Year-Old Man Comes to the Emergency Department Due to Severe