What is crystallopathy (crystal-induced arthropathy)?

From the Guidelines

Crystalopathy management should prioritize urate-lowering therapy (ULT) with allopurinol as the first-line treatment, starting at a low dose of 100mg daily and titrating up to reach a serum uric acid (SUA) target of <6 mg/dL, with a lower target of <5 mg/dL for patients with severe gout. The management of crystalopathy, including gout, pseudogout, and basic calcium phosphate crystal deposition disease, requires a comprehensive approach that includes both acute and long-term management strategies. For acute gout attacks, treatment options include NSAIDs, colchicine, or corticosteroids 1.

Key Considerations

• Long-term management involves ULT, with allopurinol being the recommended first-line treatment, starting at a low dose and titrating up to reach the target SUA level 1.
• The SUA target should be maintained at <6 mg/dL, with a lower target of <5 mg/dL for patients with severe gout, to facilitate faster dissolution of crystals and prevent recurrent crystal formation 1.
• Patients with renal impairment require adjusted dosing of allopurinol, and alternative treatments such as febuxostat or benzbromarone may be considered if the SUA target cannot be achieved 1.
• Lifestyle modifications, including weight loss, avoidance of alcohol and sugar-sweetened drinks, and regular exercise, are essential components of management to prevent recurrent crystal formation and tissue damage 1.

Imaging and Diagnosis

• Imaging techniques, such as dual-energy CT and ultrasound, can be useful in diagnosing and monitoring crystal-induced arthropathies, but more research is needed to optimize their use in clinical practice 1.
• The task force recommends a treat-to-target strategy for every patient with gout, to maintain the SUA level <6 mg/dL, which is below the saturation point for MSU to dissolve all crystal deposits 1.

Treatment Approach

• All ULTs should be started at a low dose and then titrated upward until the SUA target is reached, with SUA <6 mg/dL (360mmol/L) maintained lifelong. The choice of treatment should be based on the presence of contraindications, the patient’s previous experience with treatments, time of initiation after flare onset, and the number and type of joint(s) involved 1.

From the Research

Definition and Types of Crystalopathy

• Crystalopathy is a disease that involves crystals or crystallike particulate matter in the pathogenesis of tissue injury 2
• Crystals are solid particles with a geometric shape due to the regular ordered structure of their atoms, ions, or molecules 2
• Crystallopathies can be classified into three types in nephrology: renovascular crystallopathy (type 1), tubular crystallopathy (type 2), and urolithiasis (type 3) 2

Pathophysiological Mechanisms

• Several predominant pathophysiological mechanisms are involved in the formation of crystallopathies, including necroinflammation, chronic remodeling of tissues, and obstruction of ducts, cavities, or vessels by larger crystalline masses or stones 2
• Inflammatory and oxidative stress markers are increased in experimental crystalopathy, but can be positively modified by photobiostimulation 3

Treatment of Crystalopathy

• Colchicine is a commonly used treatment for acute gout, a form of crystalopathy, and has been shown to be effective in reducing pain and inflammation 4, 5
• Low-dose colchicine may be an effective treatment for acute gout with little or no increased risk of adverse events, while high-dose colchicine may increase the risk of adverse events 5
• Other treatments for gout include NSAIDs, glucocorticoids, and urate-lowering therapies such as allopurinol and febuxostat 4, 6
• Novel therapies, such as IL-1β antagonists and uricosurics, are also being developed for the treatment of gout 6