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Ageing block > Crystal arthritis > Flashcards

Crystal arthritis Flashcards

1
Q

Which diseases come under ‘crystal arthritis’?

A
  • Gout

- Pseudogout

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2
Q

Which crystals precipitate in gout?What kind of birefringence does it have? what is the shape of the crystals?

A
  • Urate crystals
  • Negatively birefringence
  • Long & needle shaped
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3
Q

Which crystals precipitate in pseudogout?What kind of birefringence does it have?What is the shape of the crystals?

A
  • calcium pyrophosphate crystals
  • positively birefringence
  • Small rhomboid shaped
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4
Q

What are the characteristics of gout

A
  • Tends to be acute monoarthritis
  • Typically occurs in a peripheral joint, particularly the big toe
  • When it happens, people are usually feeling well the day before i.e it is sudden
  • Max peak of pain tends to peak during 24 hours
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5
Q

What is a common differential of gout?

A

Septic arthritis (but with this people usually describe a prodrome of feeling systemically unwell)

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6
Q

What is the role of uric acid in gout?

A

-Uric acid is the final product of purine metabolism

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7
Q

Why can’t humans break down uric acid in the body?

A

-Humans have inactive uricase gene

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8
Q

Outline the metabolism of purines

A

Hypoxanthine—> Xanthine (using enzyme Xanthine oxidase)

Xanthine—> Uric acid (using enzyme Xanthine oxidase)

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9
Q

What is the threshold(s) for hyperuricaemia

A
  • In males is >0.42mmol/L
  • In females is .0.36mmol/L
  • Hyperuricaemia is more common than gout
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10
Q

What are the risk factors for development of gout?

A
  • Hyperuricaemia
  • Persistent alcohol consumption
  • Diuretic use
  • High BMI
  • Lipid disorders
  • Older age
  • Male sex
  • Genetics
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11
Q

Outline a high urate diet

A
  • Shellfish(esp oysters)
  • Marmite
  • Red meat
  • Beer(real ale)
  • alcohol
  • sweetened soft drinks
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12
Q

What can reduce fractional clearance of urate?

A
  • Alcohol
  • Donate a kidney/ have CKD
  • Use of diuretics
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13
Q

What are the clinical features of gout

A
  • Classic description of severe pain of rapid onset
  • First attack always single joint and never axial skeleton
  • Great toe MTPJ>50%
  • BUT subsequently any joint/any number of joints
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14
Q

Define Gouty Tophi

A
  • aka tophaceous gout
  • A deposit of uric acid crystals, in the form of monosodium urate crystals
  • in people with longstanding hyperuricaemia
  • pathognomic for the disease
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15
Q

Where can Gouty Tophi typically occur

A
  • Fingers
  • ears
  • bursae eg olecranon bursa
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16
Q

How can we distinguish between the radiographical features of gout and RA?

A 
Gout:
-periarticular 'hole punched' out lesions
RA:
-Marginal erosions
-Not periarticular
-On the joint margin
17
Q

Can we distinguish between gout and septic discitis radiographically?

A
  • NO
  • Gout that has spinal involvement ( which may or may not be at multiple disc levels) cannot be radiographically distinguished from a septic discitis
18
Q

How is gout diagnosed?

A

-Arthrocentesis

19
Q

Outline the therapeutic strategies in gout

A
  1. ) Dietary restriction to reduce exogenous purines:
    - eg less oysters & red meat
  2. )Xanthine oxidase inhibitors: reduce the formation of urate; this reduces endogenous purines
  3. ) Recombinant uricase:
    - reduces the formation of precipitates as this is more soluble
    - but when you stop it it can cause rebound hyperuricaemia so we barely use these
  4. ) Uricosuric agents:
    - drugs that increase renal clearance
    - But gout patients typically have renal insufficiency or failure so these agents would be useless in these pts
20
Q

Outline the drugs we may use to relieve pain in gout?

A
  1. ) NSAIDs
    - Most common as long as pt is healthy
    - eg Naproxen 500mg bd x5d
    - Avoid in renal, cardiac or liver disease
  2. ) Colchicine:
    - 1 mg STAT; 0.5mg bd x5d
    - Beware of interactions
  3. ) Prednisolone:
    - 30mg od x5d
    - Caution in DM/CCF
21
Q

List the contraindications of NSAID use

A

don’t use in the following diseases…

  • renal
  • cardiac
  • liver
22
Q

What drugs are used to prevent recurrence of gout?

A 
URATE LOWERING THERAPY:
Xanthine oxidase inhibitors...(beware of azathioprine/6-MP)
1.) Allopurinol:
-some pts get a rash
-risk of DRESS
2.) Febuxostat
-Beware theophylline
23
Q

What does DRESS stand for and what isit

A
  • Stands for drug reaction with eosinophilia and systemic symptoms
  • rare, potentially life-threatening
  • drug-induced
  • hypersensitivity reaction
  • Includes skin eruption, hematologic abnormalities, lymphadenopathy& internal organ involvement
24
Q

Why should we beware of axathioprine/6-MP when using xanthine oxidase inhibitors

A
  • 6-MP is the active metabolite of azathioprine

- azathioprine is metabolised by xanthine oxidase so if you co-prescribe, you will no longer be able to metabolise it

25
Q

What are the risk factors for calcium pyrophosphate disease(pseudogout)

A
  • ageing
  • prior joint trauma
  • familial chondrocalcinosis
  • Haemochromotosis
  • Hyperparathyroidism,hypomagnesemian and hypophosphatasia (inc Gitelman’s syndrome)
26
Q

define chondrocalcinosis

A

calcium within the joint

27
Q

What are the characteristics of CPPD

A
  • Mono or oligoarticular disease
  • Rapid onset severe joint pain
  • Peak intensity within 6-24hrs(earlier than gout)
  • fever in majority of pts (in contrast gout pts rarely get a fever, or are unaware of it if they do)
  • overlying erythema & desquamation
  • Resolution in 3-4days
28
Q

What does CPPD stand for?

A

Calcium pyrophosphate deposition disease

29
Q

compare and contrast gout crystals with those of CPPD

A

CPPD crystals are:

  • positively birefringent
  • tend to be sparse in number
  • smaller
  • more weakly birefringent
30
Q

Outline the treatment of CPPD

A
  • pretty much the same as gout
  • Currently we have no treatment that prevents long term recurrence of the disease
  • If there is significant OA you can do a joint replacement

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