Monosodium Urate Crystal Deposits Common in Asymptomatic Sons of Individuals With Gout

Asymptomatic sons of persons with gout often have hyperuricemia and undersecretion of uric acid, along with a high prevalence of monosodium urate (MSU) crystal deposition, according to the results of a community-based, cross-sectional study published in Arthritis & Rheumatology.

The investigators sought to estimate the prevalence and distribution of asymptomatic MSU crystal deposition among sons of individuals with gout. The study was conducted among sons of prior survey participants who attended the Rheumatology Clinic at the Nottingham NHS Treatment Centre. Patients with gout were mailed explanatory letters that contained study packs to be mailed to their son ≥20 years of age. Sons who were interested in participating in the survey returned a reply slip and underwent a screening process over the telephone. 

Ultimately, respondents attended a study visit in which blood and urine samples were obtained, and musculoskeletal ultrasonography that was blind to serum urate levels was performed. Images were examined for double contour sign, intraarticular or intratendinous aggregates/tophi, effusion, and power Doppler.

A total of 131 sons of patients with gout completed the evaluations. Mean age was 43.80±11.20 years; mean body mass index was 27.10±4.75 kg/m². Of the patients who were assessed, 64.1% had serum urate levels ≥6 mg/dL and 29.8% had either double contour sign or intraarticular aggregates/tophi in ≥1 joint.

All participants with MSU deposition reported involvement at a first metatarsophalangeal joint. Overall, 21.4% of the sons had intratendinous aggregates, which were associated with intraarticular MSU crystal deposits (adjusted odds ratio [aOR], 2.96; 95% CI, 1.17-7.49). None of the participants reported MSU crystal deposition with serum urate levels ≤5 mg/dL. In addition, 24.2% of participants with serum urate levels between 5 and 6 mg/dL reported ultrasonographic MSU deposition. MSU crystal deposition was associated with increasing serum urate levels (aOR, 1.61; 95% CI, 1.10-2.36) for every 1-mg/dL increase.

The investigators concluded that evaluation of patients without a family history of gout is warranted to confirm whether the threshold for MSU crystal deposition is lower in the general population. The results support the screening of high-risk individuals and discussion of early management, which should address modifiable risk factors such as being overweight, obesity, and high fructose intake, in an effort to reduce the risk of developing symptomatic gout.

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Reference

Abhishek A, Courtney P, Jenkins W, et al. Monosodium urate crystal deposits are common in asymptomatic sons of people with gout – the sons of gout study [published online May 27, 2018].  Arthritis Rheumatol. doi: 10.1002/art.40572