Crystal-Induced Arthritis
The two most common forms of crystal-induced arthritis among older adults are gout and calcium pyrophosphate dihydrate (CPPD) deposition disease. Gout in older adults has unique clinical features. The new case incidence is the same in males and females over age 60. Upper limb and polyarticular involvement are not unusual. CPPD deposition disease may present as asymptomatic chondrocalcinosis on radiographs and symptomatically as pseudogout, pseudo–rheumatoid arthritis, or pseudo-osteoarthritis. Other crystals may cause periarthritis or arthritis. Management of crystal-induced arthritis among older adults requires special considerations due to comorbid conditions and concomitant medications. Nonsteroidal anti-inflammatory drugs may be contraindicated. Steroids taken either orally or intra-articularly are often an alternative.
Key words: gout, chondrocalcinosis, pseudogout, pseudo–rheumatoid arthritis, pseudo-osteoarthritis.
Introduction
The most common forms of crystal-induced arthritis are caused by deposition of monosodium urate (MSU), as in gout, and calcium pyrophosphate dihydrate (CPPD), as in pseudogout, pseudo-rheumatoid arthritis, and pseudo-osteoarthritis). Other crystals, such as basic calcium phosphate, primarily hydroxyapatite, and calcium oxalate, may induce an inflammatory reaction in and around the joint. This article discusses the clinical characteristics of gout, CPPD deposition disease, and other crystal-induced arthritis/periarthritis among older adults.
Gout
Incidence and Prevalence
The prevalence of gout in the US population is <1% for both men and women, with more cases among men. After age 65, the prevalence increases to 5% for men and 2% for women. However, new case incidence of gout after 60 years of age is equal among men and women.1 Furthermore, the incidence of gout appears to be increasing over the past decade, especially among older individuals.2 This increase in incidence of gout may be related to the increased longevity in the general population, the increased use of medications such as diuretics and low-dose acetylsalicylic acid (ASA), and changes in dietary habits.
Factors Responsible for the Inflammation
Monosodium urate crystals have the ability to induce an inflammatory reaction after binding with immunoglobulins and other proteins. This includes the recruitment of phagocytic cells, ingestion of the crystals, and release of different mediators of inflammation.3 The acute inflammation is usually self-limited, related to the removal and dissolution of the MSU crystals or the loss of binding of immunoglobulin to the crystals.
Unique Clinical Features of Gout among Older Adults
The classic clinical manifestation of gout is well known. Acute gout presents as acute intermittent monoarthritis. Intercritical gout presents as more frequent, intermittent, less severe monoarthritis or oligo- or polyarthritis. Chronic, or tophaceous, gout presents as low-grade, persistent inflammatory mono-, oligo-, or polyarthritis. Among older adults, several clinical differences have been observed. These include an increase in polyarticular presentation, upper limb involvement, an increase incidence in women, and the finding of tophi.4 In our opinion, this early development of tophi may be due to a delay in the recognition of gout and from atypical, milder presentations of acute attacks.
Diagnosis
The gold standard for the diagnosis of gout is the identification of MSU crystals in joint aspirate during an acute attack. However, it is often impractical, particularly among older individuals, to aspirate the involved joint(s). Several criteria for the classification of gout have been developed. The 1977 American College of Rheumatology (ACR) criteria are the most frequently used (Table 1).5
In clinical practice, physicians should consider the possibility of crystal-induced arthropathy, including gout or CPPD deposition disease,