7.1 Crystal Arthropathy Flashcards
What is the most common cause of inflammatory arthritis in older people?
Gout
Why is there an increased prevalence of gout?
Longevity of life
Increased vascular diseases and use of diuretics
Renal diseases
Immunosuppressive therapy
Obesity and associated metabolic syndrome
Dietary trends
Limitations of existing therapies
What is the most common site of crystal arthropathy and why?
The big toe because it is colder and that is what causes uric acid to crystalise
what is the level of uric acd supersaturation and what happens?
0.40 mol/L this causes it to precipitate into tissues
When does a gouty attack occur?
When monosodium urate crystals are released or form de novo in the joint space
What can cause a gouty attack?
Trauma, surgery, infections and initiations of medications such as allopurinol and diuretics
What is the pathophysiology of a gouty attack?
Monosodium urate crystals are phagocytosed by leukocytes
Crystals trigger inflammation by proteins called inflammasome
The inflammasome potentiates IL-1 converting enzyme forming active interleukin 1B which acts on target tissues
This leads to the release of other inflammatory mediators such as cytokines, prostaglandins and vasoactive peptides
what is inflammasome production mediated by?
NOD like receptors protein that carries an N-terminal pyrin domain (NLRPs) or a capase-recruitment domain (CARD)
What can cause auto-inflammatory diseases?
Mutations in the genes encoding for components of the inflammasome that leads to processing and secretion of proinflammatory cytokines suck as IL-1b
What are the common sites of gout flares?
1st MTP midfoot Subtalar Ankle Knee Olecranon bursae Elbow Wrist Fingers
What are the initial investigations for asymptomatic hyperuricaemia?
Fasting lipid profile and BSL, 24h urine excretion of uric acid
What are the initial investigations for monoarticular and polyarticular gout?
FBC, CRP and blood cultures
Serum uric acid, EUC, LFTs, fasting lipid profile, BSL
Synovial fluid for gram stains, culture and crystals
What is the old standard for a diagnosis of gout?
MSU crystals
What is the appearance of Calcium Pyrophosphate Deposition Disease crystals?
Rhomboidal or rectangular shape
No as positively birefringenet as MSU - Will appear blue if they are
What is the appearance of MSU crystals?
Brightly birefringent and needle shaped
Appear yellow
What is the treatment for asymptomatic hyperuricaemia?
Assess the chance of developing gouty arthritis
- Urolithiasis, renal impairment or acute uric acid nephropathy
- Underlying overproduction
- Therapeutic interventions
What is the aim of gout treatment?
Reduce SUA levels to below 0.36 mmol/L
Prevent gouty attacks
What are the indications for urate lowering therapy?
Recurrent attacks, chronic tophaceous gout, radiographic changes, gout with coexisting nephrolithiasis or renal insufficiency, metabolic syndrome, diuretic therapy
What are the urate lowering drugs available?
Xanthine oxidase inhibitors: allopurinol
Uricase enzyme analogue: rasburicase
Increase excretion: losartan
Action on proteins preventing phagocytosis: colchcine
Glucocorticoids
NSAIDs
What are the joints involved in pseudogout?
knees, wrists, shoulders, hips and ankles
What is pseudogout?
Pseudogout results from the abnormal formation of calcium pyrophosphate (CPP) crystals in the cartilage (cushioning material between the bones), which is later followed by the release of crystals into the joint fluid.
What are the DD for pseudogout?
gout and septic arthritis
What is the diagnosis of pseudogout?
calcium pyrophosphate crystals in synovial fluid
Chondrocalcinosis on imaging
What is the treatment for pseudogout?
NSAIDs, glucocorticoids and cochicine
Joint asporation
Treat any underlying metabolic condition
What needs to be assessed with synovial fluid?
Volume, clarity, colour and viscosity
What causes opacity of synovial fluid?
Abnormally large numbers of nucleated or red blood cells
What causes translucent synovial fluid?
Acellular material such as lipids, cholesterol crystals, monosodium urate crystals
What causes different colours in synovial fluid?
Clear is normal
Yellow/yellow green: due to increasing amounts of plasma and nucleated cells (inflammatory or septic)
Red/rusty.chocolate: fresh or old blood
What is the normal viscosity of synovial fluid and what causes changes?
Normal: As exxpelled from syringe and allowed to drop it will produce a long string like extension
Decrease viscosity is due to release of proteolytic enzymes into inflamed synovial fluid
What is important to look at in synovial fluid?
WCC for septic arthritis
When should you not take fluid?
When there is a large amount of swelling as you don’t want to cause systemic infection
When should you suspect septic arthritis?
Acute monoarthirtis, worsening of chronic joint diseases in a single joint - especially if immunosuppressed
What should always be included in synvoial fluid analysis?
cell count, gram stain, cultures and crystal analyss
What should you do with suspected septic arthritis even with crystals?
Start on empiric antibiotics - vancomycin until results suggest methicillin susceptible pathogen
What is the most common cause of septic arthritis?
Staph aureus
In who is gram negative joint infections more common?
elderly, immunosuppressed, post-operative patients, indwelling catheters
What are the symptoms of disseminated gonococcaemia?
tenosynovitis, polyarthralgia, migratory arthritis and cutaneous lesions
What are the radiological features of out?
Erosions with overhanging margins
Sclerotic margins
Relatively well preserved joint space
Soft tissue trophii
What are the DD for gout?
SEPTIC ARTHRITIS
Mono: haemarthrosis, pseudogout, seronegative arthropathy
Poly: RA, psoiatic arthritis, primary generalised OA
What is the presentation of acute gout?
Severe pain, swelling, erythema
Acute onset
80% first attacks are monoarticular (1st MTP)
