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crystal arthropathy Flashcards

1
Q

what is the normal function of crystals within the body?

A

to strengthen the skeleton

to attract XS ions for removal from the body

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2
Q

describe what a crystal is

A

a homogenous solid where the ions are bonded closely in an ordered, repeating, symmetric arrangement
stable
hard
high density

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3
Q

what is a crystal arthropathy?

A

arthritis caused by crystal deposition in the lining of the joint

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4
Q

Describe the crystals seen in gout

A

negatively birefringent

needles

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5
Q

Describe the crystals seen in pseudogout

A

positively birefringent
rhomboids
more sparse distribution under the microscope

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6
Q

What is the name given to the crystals in gout?

A

monosodium urate crystals

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7
Q

what is the name given to the hard deposits formed in chronic gout?

A

tophaceous gout / tophi

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8
Q

What should you be concerned about when you see gout in a young person?

A

inborn metabolic errors

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9
Q

What is the most commonly affected joint in gout?

A

the first metatarsophalangeal joint (ie base of the big toe_

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10
Q

Name some joints that gout can affect

A 
big toe
ankle/foot
knee
finger
elbow
wrist
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11
Q

what is the key enzyme in the uric acid formation pathway that can be targeted by treatment?

A

xanthine oxidase

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12
Q

What is the serum level of uric acid that under which, there is negligible risk of gout?

A

0.3 mmol/L

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13
Q

At what serum level of uric acid is there some risk of crystal deposition?

A

0.36 mmol/L

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14
Q

at what level of uric acid is the serum supersaturated and urate crystal deposition likely?

A

0.42 mmol/L

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15
Q

What is the primary method of excretion of uric acid?

A

renal

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16
Q

What are the sources of purines in the body

A

diet
purine synthesis
tissue nucleic acids eg DNA and RNA

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17
Q

What does xanthine oxidase do?

A

converts purines to uric acid

specifically converting purines to hypoxanthine and hypoxanthine to xanthine

18
Q

What type of cells are responsible for the inflammatory response seen in gout?

A

WBCs eg macrophages

19
Q

What is the main reason for hyperuricaemia?

A

underexcretion of uric acid

20
Q

What is the major risk factor for gout?

A

hyperuricaemia

21
Q

when would you not measure the level of uric acid in the blood?

A

during an acute attack as it can be paradoxically low

22
Q

List some causes of under excretion of uric acid

A 
alcohol
renal impairment 
hypertension 
metabolic syndrome 
obesity 
diabetes 
drugs: low dose aspirin, diuretics esp thiazides, cyclosporin, tacrolimus, ethambutol and pyrazinamide
23
Q

What are the causes of overproduction of uric acid?

A

alcohol drinks
diet - XS meat, shellfish, offal, fructose sweetened
metabolic syndrome
myeloproliferative disease and cytotoxic drugs
psoraisis

24
Q

Name a differential diagnosis of gout and why it is a differential

A

joint sepsis - it is the only other condition where the skin is red and shiny

25
Q

What are the common precipitants of an attack?

A 
aggressive treatment for hypouricaemia
alcohol or shellfish binges 
sepsis
acute MI 
dehydration
26
Q

What is the appearance of gout on XR?

A

punched out periarticular erosion
joint space narrowing
soft tissue calcification and crystal deposition

27
Q

What is the long term preventative treatment for gout?

A

allopurinol or febuxostat ie the xanthase oxidase inhibitors

28
Q

what must you do when you start sb on long term preventative treatment for gout?

A

Give them drugs for acute gout treatment initially as starting sb on preventative treatment can precipitate a gouty attack - so start on colchidine or NSAID

29
Q

what is the aim of preventative treatment?

A

To bring serum uric acid level to <300mmol/L

30
Q

What is the principle for allopurinol dosing?

A

start low, go slow - aka start with a low dose and titrate upwards according to the serum uric acid level

31
Q

What would you do if you were giving allopurinol to sb with renal failure and why?

A

reduce the dose - as allopurinol is excreted by the kidneys and if the kidneys can’t excrete, then levels of the drug build up in the body

32
Q

What is the name given to the crystals deposited in pseudogout?

A

calcium pyrophosphate crystals

33
Q

What are the typical joints affected by pseudogout?

A 
the MCPs in the hand
wrists
knees
ankles 
most common in knee
34
Q

How does pseudogout present?

A 
acute monoarthritis 
severe pain
stiffness 
swelling 
redness
35
Q

How would you distingush OA from pseudogout?

A

pseudogout:
joints that are involved
inflammation - 4 pillars
superimposition of acute attacks on chronic

36
Q

What are the triggers of an acute attack in pseudogout?

A

direct trauma to the joint
surgery
blood transfusion, IV fluid
spontaneous - no obvious trigger

37
Q

What would an XR of the knee show in pseudogout?

A

chondrocalcinosis - deposition of calcium in the cartilage

38
Q

Name some metabolic disorders that may be associated with pseudogout esp. in a young person?

A

haemochromatosis
hyperparathyroidism/hypoparathyroidism
acromegaly
hypomagnesaemia and hypophosphataemia

39
Q

How is pseudogout managed?

A

acute attacks - NSAIDs, analgaesia, aspirate the joint and give steroid injections
long term - trial of methotrexate, hydrochloroquine, synovectomy or surgery

40
Q

What is the critical diagnostic test in gout/pseudogout?

A

joint aspiration!

41
Q

Give some points you would mention to a pt to educate them about prevention of gout

A 
prevent dehydration 
lose weight 
reduce alcohol intake 
reduce red meat intake 
add more dairy products to the diet

MSK (12 decks)

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