Revision List Rheum Flashcards
What is a crystal?
Homogenous solid, stable high density, hard
When are crystals pathological?
- Deposition causes inflammatory response and tissue damage
2. Deposition at abnormal sites
Give 3 examples of pathological crystals?
- Joints: Crystal arthropathies, urate, calcium pyrophosphate, hydoxypatite
- Kidney: stones - calcium oxalate (nephrolithiases)
- Gallbladder: cholesterol
What is crystal arthropathy?
Arthritis caused by deposition of crystals in joint lining
What is gout?
Monosodium urate crystal deposition in the joints causing inflammation
Epidemiology of gout?
M
>40
Risk factors of gout?
- Purine rich foods e.g. red meat
- High saturated fat diet
- High alcohol intake
- High fructose intake
- Drugs - low dose aspirin
- IHD
Renal causes of gout?
URAT1 transporter defect
Diuretics
High insulin levels
All impair uric acid excretion
What can cause increased production of urate?
- Metabolic syndromes: hyperlipidaemia
- Proliferative: myelo/lymphoproliferative disorders, cytotoxic drugs
- Psoriasis
- Diet: alcohol, XS meat, shellfish, meat extract, yeast extract, fructose sweetened drinks
What is the pathophysiology of gout?
Xanthine oxidase controls hypoxanthine –> xanthine –> uric acid and excreted by kidney - not very efficient –> hyperuricaemia
Normal serum uric acid levels?
0.3micromol/l
Hyperuricaemia plasma levels?
> 0.36umol/l
Causes of underexcretion of urate?
- Alcohol
- Renal impairment
- Hypertension
- Hyperthyroid/PTH
- Obesity, diabetes
Clinical presentation of acute gout?
Hot swollen red joint
Painful
Crescendo over 6-12 joint
Usually 1st MTP
Clinical presentation of chronic polyarticular gout?
Rare only in elderly on diuretics+renal failure
Clinical presentation of chronic trophaceous gout?
Persistently high levels of uric acid crystals –> large crystal depositis –> irregular nodules on fingers, forearms, achilles tendon
Asymmetrical tophi - chalky appearance under skin
What are tophi?
0nion like aggregates of MSU with inflammatory cells
How do tophi cause damage?
Cause deformity, crepitus, and decreased movement
May secrete proteolytic enzymes causing punched out lesions
Precipitators of acute gout attack
- Sudden cessation/aggressive introduction to hypouricaemic therapy
- Alcohol, shellfish binges
- Sepsis/MI/Acute severe illness
- Trauma, surgery, dehydration
Diagnosing gout?
- Clinical exam
- Joint aspiration fluid - microscopy and polarised light, gram stain exclude septic arthritis as cannot co-exist
- Serum UA raised
- Imaging - x-rays chronic gout - areas of sclerosis, punched out lesions, areas of sclerosis
Non pharmacological management of gout?
Weight loss, decrease alcohol, avoid shellfish, avoid purine rich food
Treatment of Acute Gout?
- NSAIDs - naproxen, ibuprofen
- Colchicine Se: diarrhoea, abdominal pain
- IM/oral/intra-articular corticosteroid e.g. prednisolone
Prevention of Gout?
- Stop diuretics e.g. thiazides, switch to ARB
- Allopurinol act on Xanthine oxidase - start 3 weeks after acture episode SE: rash, fever, decreased WCC
- Febuxostat: non purine xanthine oxidase inhibitor