Bone Erosions Detected in 44% of Patients With Gout

In their study of the prevalence of ultrasound-detected bone erosion in a population of gout patients, Wu and colleagues have shown that almost half of patients with gout, as diagnosed by ACR/EULAR criteria, have evidence of anatomic alteration of bone. It should come as no surprise to rheumatologists that their key finding — 44% of patients show bony erosion by ultrasound (US) — reinforces the notion of the utility of US as a diagnostic tool in the rheumatology outpatient setting, but also the destructive nature of gouty arthritis.

From this practitioner’s perspective, one informed by a 40-plus year obsession with the clinical and therapeutic aspects of gout, this study confirms the very sensitive nature of US examination relative to conventional radiographs. I have long been accustomed to performing radiographs of the feet of new gout patients to look for erosive disease. Although the addition of digital X-ray has helped to more readily identify tophaceous deposits in the soft tissues and has made it easier to detect erosions in joints affected by gout than before, X-ray is still a relatively insensitive diagnostic tool.

Rheumatologists using US are familiar with the other signature findings in acute and chronic gout, including the presence of color power Doppler (CPD) signal indicating active inflammation, synovial thickening, a “snow storm” pattern (indicative of urate deposits within the joint), the very characteristic “double contour” sign and the presence of discrete tophi. For rheumatologists not performing US in their clinics, this should be clarion call to get on board.

The second “takeaway” for me from this article is that gout is a more destructive disorder than we have thought. Though obsessed with erosions developing in rheumatoid arthritis, rheumatologists don’t think of gout in the same way. Although disease modification is a basic tenet of management in rheumatoid arthritis, the disease-modifying benefit of potent urate-lowering therapy in gout patients is not thought of in the same vein.

Patients with gout who are more than 60 years old are almost three times more likely to have US-detected erosions than patients under 40 years. If gout has caused erosive changes in 44% of patients in this cohort, and erosions — as shown by the authors — are a function of duration of disease, we should be intervening sooner with urate-lowering therapies to prevent disease progression and possibly even reverse radiographic changes.

Gout is a common and complex form of arthritis that occurs in response to monosodium urate crystals building up in joints, bones and soft tissues. Several interacting processes may cause this debilitating disease, including metabolic disorders, genetic factors and diet, all of which result in hyperuricemia. As one of the most common crystal-induced arthropathies, gout can manifest in self-limited attacks or chronic hyperuricemia with ongoing inflammation and joint destruction.

In the study by Wu and colleagues, the most common area for gout to attack is the first metatarsophalangeal joint or the joint at the base of the big toe. It is characterized by sudden severe pain, swelling, heat, and redness in the affected joint. When crystals form in and around the joints, bone erosion ensues causing anatomical damage, which is associated with functional disability, joint deformity and ongoing pain.

Few past studies have focused on bone erosion among gout patients. This study found that ultrasound imaging is superior to other types of imaging techniques for detecting early bone destruction; additionally, controlling urate levels and deposition may be the most effective way to decrease disability associated with this disease.