Gout Gout may be primary, due to overproduction or underexcretion of uric acid, or secondary. This disease is caused by the deposition of monosodium urate monohydrate crystals in the joints; the crystals can be seen with polarizing microscopy (shown). Although gout is associated with hyperuricemia, gout attacks are not triggered by a particular level of uric acid; the typical trigger is acute changes in the level of uric acid. All patients with gout have hyperuricemia; however, not all patients with hyperuricemia have gout. Hyperuricemia may also be found in patients administered diuretics, as well as in those taking niacin or low doses of aspirin. Note that serum uric acid may be normal at the time of an acute attack of gout. Which of the following is a secondary cause of gout? A. B. C. D. E.
Renal failure Lead poisoning Glycogen storage disease Myeloproliferative disease All of the above
Answer: E. All of the above Secondary causes of gout are numerous and include myeloproliferative diseases, renal failure, renal tubular disorders, lead poisoning, hyperproliferative skin disorders, and enzymatic defects. Sleep apnea has recently been shown to be an independent risk factor for gout. The classic presentation of gout is pain, edema, and inflammation. Podagra refers to involvement of the metatarsophalangeal (MTP) joint in the first toe and is present in 50% of cases. There is a preference for peripheral locations, possibly because serum urate has decreased solubility at these sites due to the cooler temperatures of the digits, which enables urate to precipitate.[2,4] The photograph demonstrates multiple gouty deposits in the hands of an affected individual.
Gout attacks begin abruptly and typically reach maximal intensity within 8-12 hours. They involve activation of inflammasomes (multiprotein cytoplasmic complexes that activate caspases) and the production of interleukin-1 (IL-1). Attacks may resolve spontaneously in a couple of weeks, and patients may return to normal between attacks. If left untreated, gout may begin to involve more joints, larger joints, or more proximal joints; attacks may also occur more frequently and last longer. This image from an affected patient shows involvement of the elbow, a finding that is more common in later stages of gout. Tophi are collections of urate crystals in the soft tissues and should not be surgically removed unless there is superinfection or the presence of secondary symptoms. Delayed wound healing can occur in up to 50% of patients.[2,6] Which of the following is a classic radiographic appearance of gout? A. B. C. D.
Polyarticular symmetrical involvement Joint-space erosions and decreased bone mineral density Punched-out erosions with overhanging margins Extensive soft-tissue calcifications
Answer: C. Punched-out erosions with overhanging margins The classic radiographic appearance of gout is punched-out periarticular lesions with overhanging edges (yellow arrow), normal bone mineral density, and hyperdense soft-tissue tophi (red arrow). Typically, there is preservation of the joint space until late in the disease process. Involvement is asymmetrical, which helps to differentiate gout from systemic arthropathies, such as rheumatoid disease. Imaging studies may show findings consistent with gout, but these findings are not diagnostic by themselves. However, imaging features can be used to evaluate the severity of the disease and to detect the involvement of additional joints.[2,7]
The tophi in gout typically appear hyperdense and may develop calcifications (arrows). The tophi may be readily identified on magnetic resonance imaging (MRI) as well-defined, periarticular masses that have varying signal intensities, depending on the amount of uric acid, granulation tissue, and edema that is present. Ultrasonography, however, is the most sensitive imaging modality to detect tophi.[2,8] What color is the synovial fluid aspirated from patients with gout? A. B. C. D.
Clear or white Yellow or orange Green Red
Answer: A. Clear or white Synovial fluid obtained from a patient with tophaceous gout is shown. Formal diagnosis of gout requires aspiration of joint fluid, which is a safe procedure associated with a 0.1% risk of septic arthritis. Only a small amount of fluid is typically needed for crystal analysis. Depending on the clinical circumstances, it may be important to exclude septic arthritis as the etiology of crystalline arthropathy. White blood cell (WBC) counts may be elevated (