Gout Tophi (Tophus) - What Is It?

Characteristic Deposits In and Around the Joints

Gout tophus
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Tophi are aggregates of sodium urate monohydrate crystals which are deposited in and around the joints of gout patients. There are three stages of gout: asymptomatic hyperuricemia, interval gout (episodes of acute gouty arthritis punctuated by asymptomatic periods), and chronic gouty arthritis. It is during the third phase, chronic gouty arthritis, when tophi usually appear. Tophi may be suspected as early as the acute gouty arthritis phase though.

When Tophi Form

During the chronic gouty arthritis phase, there are no pain-free periods. The time frame between an initial gout attack to the chronic gouty arthritis phase with visible tophi varies in studies of untreated gout patients. Study results (Hench, P. The diagnosis of gout and gouty arthritis. J Lab Clin Med 220: 48–55. 1936.) revealed that the average time from initial gout attack to the start of chronic arthritis or the development of visible tophi was 11.6 years. In a study involving more than 1,100 primary gout patients, those without tophi had serum urate levels of 10.3+/-1.3 mg/dl. Those with extensive tophi formation had serum urate levels of 11.0+/-2.0 mg/dl.

Why Tophi Form

The rate of tophi formation correlates with the severity and duration of hyperuricemia. Tophaceous gout occurs because of the body's inability to eliminate urate as quickly as it is produced. As excess urate collects, urate crystal deposits can form.

While the level of serum urate is the primary factor associated with tophi formation, there can be other contributory factors, including: early age of gout onset, long periods of active but untreated gout, an average of 4 gout attacks per year, and upper extremity and polyarticular involvement.

Early development of tophi -- in people who have had gout for less than 10 years -- occurs in about 15% of people.

Creatinine clearance is an independent factor that has been linked to early tophi formation.

Where Tophi Form

Urate crystal deposits (i.e., tophi) be found in the cartilage, synovial membranes, tendons, and soft tissue. While tophi can be found anywhere on the body, it is most common in the fingers, wrists, ears, knees, olecranon bursa, and pressure points (e.g., ulnar aspect of the forearm, Achilles tendon). In connective tissue, tophi may be found in renal pyramids, heart valves, and sclerae.

Tophi Characteristics

Tophi are characteristically painless, however acute inflammation may develop around them. There can be destruction of the joints and deformity can occur, especially of the hands and feet. The skin that lies over a tophus can become taut and eventually ulcerate. A white chalky or pasty substance, composed of urate crystals, may be expelled from the ulcerated tophus. Tophi can be detected with ultrasonography, MRI, and CT scan. The most detailed images of tophi come from CT scan.

Quality of Life

Researchers considered the impact of tophi and the frequency of acute gout attacks on health-related quality of life. The study (Health and Quality of Life Outcomes 2012, 10:117 ) involved 620 patients with self-reported gout, 12.3% of whom had tophi. There was decreased health-related quality of life associated with both the presence of tophi and gout flares.

Sources:

Primer on the Rheumatic Diseases. Arthritis Foundation. Thirteeth Edition. Page 243.

Kelley's Textbook of Rheumatology. Elsevier Saunders. Ninth Edition. Volume II. P.1558-1560.

Hench, P. The diagnosis of gout and gouty arthritis. J Lab Clin Med 220: 48–55. 1936.

Reduced Creatinine Clearance Is Associated With Early Development of Subcutaneous Tophi in People With Gout. BMC Musculoskeletal Disorders. December 21, 2013.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3878111/

Tophi and Frequent Gout Flares Are Associated With Impairments to Quality of Life, Productivity, and Increased Healthcare Resource Use: Results From a Cross-sectional Survey. Khanna PP et al. Health and Quality of Life Outcomes. September 22, 2012.
http://www.ncbi.nlm.nih.gov/pubmed/22999027

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