Crystal Arthropathies Flashcards
In basic terms, what is a crystal arthropathy
When excess uric acid gets deposited in joints resulting in the syndrome of Gout
Endogenous production of uric acid from the degradation of purine contributes to what amount of the urate pool
2/3rd
What usually happens to uric acid in the body
The majority is excreted via the kidney and the remainder is eliminated into the biliary tract and subsequently converted by colonic bacterial uricase into allatoin.
In the vast majority of patients with gout, what is the most common cause of hyperuricaemia
Reduced efficiency of renal urate clearance
What results in the over production of uric acid
Malignancy, severe exfoliative psoriasis, ethanol and cytotoxic drugs, inborn errors of metabolism and HGPRT (Hypoxanthine-guanine phosphoribosyltransferase) deficiency
What results in the under-excretion of uric acid
Renal impairment, hypertension, hypothyroidism, exercise, starvation, dehydration, lead poisoning
Gout tends to effect what area of the population
Elderly males
Why are males more prone to gout
They have higher urate levels
Why is gout rare in younger women
Oestrogen has a uricosuric (increased excretion of uric acid in the urine) effect
What are the factors that make increasing age a risk factor for gout
An increase in serum Uric Acid levels due to reduced renal function
Increased use of diuretic and other drugs that raise serum uric acid
Age related changes in connective tissues which may encourage crystal formation and an increase prevalence of osteoarthritis
How is Gout diagnosed
Aspiration of the joint and checking for crystals - polarized light microscopy of synovial fluid will show negatively bi-refringent urate crystals
Serum urate is only useful in chronic settings
State the management of acute gout
NSAID’s, colchicine if intolerant to NSAID’s, can give steroids if feel necessary
Where does gout tend to occur
metatarsophalangeal joint of the big toe
How can gout be prevented
Lose weight, avoid prolonged fasts, alcohol excess, purine-rich meats and low dose aspirin
When should prophylactic treatment for gout be started
If there has been more than one attack in 12 months, tophi or renal stones
State the aim of prophylaxis of gout
To reduce attacks and prevent damage caused by crystal deposition
State the main mode of prophylactic treatment of gout
Allopurinol and titrate from 100mg24 increased every 4 weeks until plasma urate <0.3mmol/L
State the different drugs used to lower uric acid
Allopurinol (Xanthine Oxidase Inhibitor), Febuxostat, Urisuric Agents (sulphinpyrazone, probenecid, benzbromarone), canakinumab
What are the specific rules used when using medications to lower uric acid
Wait until the acute attack settles
Use prophylactic NSAIDS or lose dose colchicine/steroids until the urate level is normal
Adjust Allopurinol dose according to renal function
Acute Calcium Pyrophosphate Deposition Disease (pseudogout)
Acute monoarthropathy usually of larger joints in the elderly
Chronic CPPD (psuedogout)
Inflammatory rheumatoid arthritis like symmetrical polyarthritis with synovitis
risk factors for psuedogout
Old age, hyperparathyroidism, haemochromatosis, hypophosphataemia
Diagnosis of pseudogout
Polarized light microscopy of synovial fluid shows weakly positively birefringent crystals
Soft tissue calcium deposition on X-ray
Management of acute attack of pseudogout
Cool packs, rest, aspiration, intra-articular steroids, NSAIDS and colchicine may prevent attacks
Management of chronic psuedogout
Methotrexate and hydroxychloroquine
What is polymyalgia rheumatica
Inflammatory condition of the elderly with close relationship to giant cell arteritis
Presentation of polymyalgia rheumatica
Sudden onset of shoulder and or pelvic girdle stiffness, with high ESR, anaemia, malaise, weight loss, fever, depression, arthralgia and synovitis
Diagnosis of polymyalgia rheumatica
Compatible history and dramatic steroid response
Treatment of polymyalgia rheumatica
Prednisolone 15mg per day, 18-24 month course given after. Do bone prophylaxis.
