Crystal-induced arthropathies are a group of diseases in which crystals form within joints. The different entities are determined based on the type of crystal, and generally, they all lead to joint inflammation, pain, and disability.
Gout
Gout is an inflammatory disease in which monosodium urate (MSU) crystals are deposited within joints and other extra-articular tissues.
- Uric acid is produced as a product of purine metabolism. Excessive production/intake or reduced elimination leads to its accumulation (hyperuricemia).
- Gout can be primary (most cases, appears in adult men) or secondary to metabolic or systemic disease, and certain drugs (thiazides, cyclosporin).
- Lesh-Nyhan syndrome is a rare, X-linked disorder caused by HPRT deficiency leading to the excessive degradation of purines into urate. Presents with mental retardation, and the consequences of hyperuricemia (gout, nephropathy).
- Renal damage is a major complication of gout (urate nephropathy and nephrolithiasis).
- Cold temperature, low pH, dehydration and injury can contribute to gouty inflammation.
- Gout can manifest in sites of previous fractures.
Stages
- Asymptomatic hyperuricemia. Urate level of >8mg/dL, clinically silent.
- Acute gouty arthritis. Presents as an inflammation of a single joint, typically of the 1st MTP joint. Sudden, severe pain and disability, reddening and swelling. Most frequently, associated with alcohol consumption. Resolves within days to weeks.
- Intercritical gout. Refers to the symptom-free period in-between the gouty