Crystal Arthropathies Flashcards
Gout Pseudogout PMR
Crystal Arthropathies
Name 2 characteristics common in crystal deposition diseases
Crystal deposition diseases are characterised by:
- Desposition of mineralised material
- In joints and peri-articular tissue
Excretion of uric acid allantoin - physiology (3)
70% by kidney
Rest by biliary tract > GI bacterial uricase
Crystal Arthropathies
What are the chemical compounds that are pathogenic in these cases?
Gout = ?
Pseudogout = ?
Gout = monosodium urate
Pseudogout = calcium pyrophosphate dihydrate (CPPD)
3 categories: causes of hyperuricemia
- Overproduction of uric acid
- Underexcretion of uric acid
- Excess intake of uric acid - alcohol
4 causes of overproduction induced hyperuricemia
- Congenital - inborn errors of metabolism, HGPRT def
- Severe exfoliative psoriasis
- Malignancy - lymphoproliferative, tumor lysis syndrome
- Drugs - cytotoxic drugs
Explain how alcohol causes hyperuricemia (5)
Excess intake of uric acid
Alcohol - rich in purines e.g. beer
Metabolism of ethanol > acetyl CoA leads to adenine nucleotide degradation
Results in increased formation of adenosine monophosphate (uric acid precursor)
Raised serum lactic acid level - inhibition of uric acid excretion
6 causes of under excretion induced hyperuricemia
Renal impairment, dehydration HTN Hypothyroidism Drugs - low dose aspirin, diuretics, cyclosporin Lead poisoning
What is Lesch Nyan syndrome/HGPRT deficiency Hereditary pattern Cognitive manifestations (3) Physiologic manifestations (2)
Hereditary pattern: x-linked recessive Cognitive manifestations - intellectual disability - aggressive, impulsive behaviour - self-mutilation Physiologic manifestations - gout -renal disease
Prevalence of gout - gender distribution
Men have increased prevalence of gout across all ages, less in older age
Why is gout very rare in young women
Why is gout more prevalent after menopause
estrogen has uricosuric effect
urate levels rise after menopause so gout becomes more prevalent
Gout Clinical Dx (3)
History - dehydration
Examination - typically first MTP
Joint aspiration
Management gout (3)
Acute flare 3 drugs
Therapies to lower uric acid
Address risk factors
What are the 3 drugs used in acute flares of gout
Colchicine 500mg BD (SE diarrhea)
NSAIDs - high dose
Steroids
When would you use oral steroids in an acute flare of gout?
if the gout is polyarticular ie more serious
Indications where the first attack is treated (4)
Single attack of polyarticular gout
Tophaceous
Renal insufficiency
Urate calculi - in kidneys
When would you treat gout prophylactically [4]
What to use in prophylactic treatment of gout? SE [3]?
If >1 attack in 1y
Tophi
Renal calculi
Certain malignancies - tumor lysis syndrome
Allopurinol
SE: rash, fever, decreased WCC
What are the therapies to lower uric acid? [3]
Xanthine oxidase inhibitor - allopurinol, febuxostat
Uricosuric agents
Canakinumab - IL-1 antagonist
What are 3 uricosuric agents
Sulphinpyrazone
Probenecid
Benzbromarone
What are 4 metabolic syndromes and one social factor that is associated with gout
- Obesity
- DM
- Hypercholesterolemia
- HTN
- Social factor - smoking
Why wait 3 weeks until the acute attack has settled before attempting to reduce urate level? What to give patient in the meantime?
Starting drugs to reduce urate level can trigger an acute attack of gout.
Give NSAIDs to cover or colchicine in the meantime.
Pseudogout epidemiology
Elderly, females
Pseudogout - characteristics (4)
Erratic flares
Acute onset of
red hot swollen joint
deposition of CPPD crystal
Pseudogout -risk factors [3]
Hyperparathyroidism
Haemochromatosis
Hypophosphatemia
Triggers of pseudo gout (2)
Trauma and intercurrent illness
2 features of CPPD crystals on polarized light microscopy
X-ray appearance
Rhomboid shaped
Positive birefringence
X-ray: associated with soft tissue calcium deposition (chondrocalcinosis) in the knee this can be seen as linear calcifications of the meniscus and articular cartilage
Management of pseudogout (2)
NSAIDS
IA steroids
PMR
3 symptoms
Sudden onset shoulder and/or pelvic girdle stiffness
High ESR and anemia
Arthralgia/synovitis occasionally
PMR epidemiology - gender distribution, age
F:M 2:1
>70 yo
Diagnosis of PMR
History compatible
Age > 50
ESR > 50
Dramatic steroid response
DDX of PMR (6)
Myalgic onset inflammatory joint disease Underlying malignancy Inflammatory muscle disease Hypo/hyperthyroidism Bilateral shoulder capsulitis Fibromyalgia
Treatment of PMR (1)
Prednisolone 15mg initially for 18-24 month course
What prophylactic measure should be taken in conjunction with PMR treatment?
DEXA bone scanning during course of treatment with steroids
Investigations gout [3] and what result would they show if dx was gout
Polarised light microscopy of synovial fluid showing negatively birefringent urate crystals
Serum urate - usually raised but may be normal
Radiographs - soft tissue swelling early stages, punched out erosions (non-sclerotic changes) late stages
Prevention Gout
Lifestyle modification [4]
Lose weight
Avoid prolonged fasts
Avoid alcohol excess
Avoid purine rich meats
