Crystal Arthropathy Flashcards
What are crystal deposition diseases characterised by?
Characterised by deposition of mineralised material within joints and peri-articular tissue
Which crystal is implicated in gout?
Monosodium urate
Which crystal is implicated in pseudogout?
Calcium pyrophosphate dehydrate (CPPD)
Which crystal is implicated in calcific periarthritis/tendonitis?
Basic calcium phosphate hydroxyl-apatitie (BCP)
How does gout present?
- Typically affects 1st MTP
- Occurs overnight: usually a niggle going to bed
- Extremely painful
- Red shiny overlying skin: may peel
- Chalky white spots of crystal deposits
Where does urate in the body come from?
- Endogenous production of uric acid by degradation of purines = 2/3
- Dietary = 1/3
What happens to uric acid in the body?
- 70% excreted by the kidney
- Remained eliminated into the biliary tract and converted to allantoin by colonic bacterical uricase
Why does hyperuricaemia occur in gout?
Results from reduced efficiency of renal urate clearance
What are the 2 mechanisms of hyperuricaemia?
- Overproduction
- Under excretion
What can cause overproduction of uric acid?
- Malignancy e.g lymphoproliferative, tumour lysis syndrome
- Severe exfoliative psoriasis
- Drugs e.g. ethanol, cytotoxic drugs
- Inborn errors of metabolism
- HGPRT deficiency
What can cause under excretion of uric acid?
- Renal impairment
- Hypertension
- Hypothyroidism
- Drugs e.g. alcohol, low dose aspirin, diuretics, cyclosporin
- Exercise, starvation, dehydration
- Lead poisoning
What happens once there is saturation of uric acid in the body?
Crystals begin to form. Crystals irritate the synovium causing inflammation leading to an inflammatory response
What is Lesch Nyan syndrome caused by?
HGPRT deficiency
What are the features of Lesch Nyan syndrome?
- X-linked recessive
- Intellectual disability
- Aggressive and impulsive behaviour
- Self mutilation
- Gout
- Renal disease
What are the risk factors for gout?
- Obesity
- Hypertension
- Hypercholesterolemia
- Diabetes mellitus
- Alcohol
- Diuretics
- Dehydration
What is the prevalence of gout in the UK?
- Predominantly a disease of older men
- Gout is rare in young women due to the effect of oestrogen
How is gout diagnosed?
History
- Classical
- Episodic in nature
Examination
Differential
Investigations: Aspiration (looking for crystals, exclude infection)
- Sent for gram stain and culture
- Polarising microscopy
How should an acute flare of gout be treated?
- NSAIDs
- Colchine
- Steroids (IA, IM, oral)
When is hyperuricaemia treated?
1st attach not treated unless
- Single attack of polyarticular gout
- Tophaceous gout
- Urate calculi
- Renal insufficiency
Treat if 2nd attack within 1 year
Prophylactically prior to treating certain malignancies
DO NOT treat asymptomatic hyperuricaemia
How can uric acid be lowered?
- Xanthine oxidase inhibitor e.g. Allopurinol
- Febuxostat
- Uricosuric agents e.g. sulphinpyrazone, probenecid, benzbromarone
- Canakinumab (IL1 anatagonist)
What are the rules for lowering uric acid levels?
-Wait until the acute attack has settled before attempting to reduce the urate level
-Use prophylactic NSAIDs or low dose colchicine/steroids until urate level normal
Adjust allopurinol dose according to renal function
How does pseudogout present?
- Usually affects elderly women
- Erratic flares
- Can be idiopathic, familial or metabolic
- Triggered by trauma or intercurrent illness
- Usually quick onset and settles within a week
How is pseudogout managed?
- NSAIDs
- I/A steroids
- No prophylactic therapies
- Rest and splinting to make patient comfortable
What is polymyalgia rheumatica?
Inflammatory condition of the elderly with a close relationship with GCA (most common of the systemic vasculitides characterised by involvement of the large vessels
What is the cycle of polymyalgia rheumatica?
- Polymyalgia rheumatica
- Giant cell arteritis
- High ESR and anaemia
How does polymyalgia rheumatica present?
- F:M 2:1
- Usually >70 years
- Sudden onset of shoulder +/- pelvic girdle stiffness
- ESR >45 often 100
- Anaemia
- Malaise, weight loss, fever, depression
- Can get arthralgia/synovitis occasionally
How is a diagnosis of polymyalgia rheumatica made?
- Compatible history
- Age >50
- ESR>50
- Dramatic steroid response
- No specific diagnostic test
What is the differential diagnosis for polymyalgia rheumatica?
- Myalgic onset Inflammatory joint disease
- Underlying malignancy (e.g Multiple myeloma, lung cancer)
- Inflammatory muscle disease
- Hypo/ hyperthyroidism
- Bilateral shoulder capsulitis
- Fibromyalgia
How is polymyalgia rheumatica treated?
- Prednisolone 15mg per day initially
- 18-24 mth course
- Bone prophylaxis
