Crystal Arthropathy

Question 1

What crystals are associated with gout?

Answer 1

Monosodium urate

Question 2

What crystals are associated with pseudogout?

Answer 2

Calcium pyrophosphate dihydrate

Question 3

What crystals are associated with calcific periarthritis/tendonitis?

Answer 3

Basic calcium phosphate hydroxy-apatite

Question 4

What joint is affected by gout?

Answer 4

The first metatarpalpharyngeal joint

Question 5

What are the symptoms of gout?

Answer 5

Patients often report of a sore joint before they go to bed and a red, hot, inflamed, excruciatingly painful joint when they wake up
Gout tophi can be present (white chalky substance)
Tophi can also develop on the elbows and behind the ears

Question 6

What are the sources of uric acid/urate in the body?

Answer 6

2/3 comes from degradation of purines

1/3 comes from diet

Question 7

What is the cause of gout?

Answer 7

Hyperuricaemia- most often caused by reduced renal clearance of uric acid

Question 8

What are the causes of overproduction resulting in hyperuricaemia?

Answer 8

• Malignancy e.g lymphoproliferative, tumour lysis syndrome
• Severe exfoliative psoriasis
• Drugs e.g. ethanol, cytotoxic drugs
• Inborn errors of metabolism
• HGPRT deficiency

Question 9

What are the causes of underexcretion resulting in hyperuricaemia?

Answer 9

• Renal impairment
• Hypertension
• Hypothyroidism
• Drugs e.g. alcohol, low dose aspirin, diuretics, cyclosporin
• Exercise, starvation, dehydration
• Lead poisoning

Question 10

What are the characteristics of Lesch Nyhan syndrome?

Answer 10

X-linked recessive disease 
HGPRT deficiency 
Results in:
-Intellectual disability
-Aggressive and impulsive behaviour
-Self mutilation 
-Gout
-Renal disease

Question 11

What are the risk factors for gout?

Answer 11

Obesity
Alcoholics
People on diuretics
People who are very active and prone to dehydration
Age
Male sex

Question 12

How long does an untreated episode of gout last?

Answer 12

~7-10 days

Question 13

How many joints does gout tend to affect?

Answer 13

Polyarticular gout is very rare, with infection of one or two joints being more common

Question 14

What investigations can be helpful in gout?

Answer 14

Fluid aspiration from affected joint to identify gout crystals in fluid
Fluid can also be sent for microscopy and culture to rule out septic arthritis
Uric acid levels can be measured but these are not diagnostic in acute episodes of gout

Question 15

How is an acute flare of gout treated?

Answer 15

NSAIDs, colchicine and steroids (can be IV, IA, IM or oral)
One acute episode does not call for prophylaxis unless there are risk factors or it is polyarticular
If a second episode occurs within a year then prophylaxis should be started

Question 16

When should hyperuricaemia be treated?

Answer 16

A first attack of hyperuricaemia does not need treated unless there is polyarticular gout, tophaceous gout, urate calculi or renal insufficiency present
Asymptomatic hyperuricaemia should not be treated

Question 17

How are uric acid levels lowered medically?

Answer 17

• Xanthine oxidase inhibitor e.g. Allopurinol
• Febuxostat
• Uricosuric agents e.g. sulphinpyrazone, probenecid, benzbromarone
• Canakinumab (rarely used)
  Allopurinol and febuxostat first line treatments

Question 18

What are the rules for lowering uric acid levels?

Answer 18

• Wait until a few weeks after the acute attack has settled before attempting to reduce the urate level
• Use prophylactic NSAIDs or low dose colchicine/steroids until urate level normal
• Adjust allopurinol dose according to renal function
• Address cardiovascular and lifestyle factors

Question 19

What joint is affected in pseudogout?

Answer 19

The knee

Question 20

How does pseudogout typically present?

Answer 20

Commonly presents as a hot inflamed knee in elderly females with a history of erratic flares of a painful knee

Question 21

What are the causes and triggers of pseudogout?

Answer 21

Can be idiopathic, familial or metabolic

Triggers can include trauma or intercurrent illness

Question 22

How is pseudogout treated?

Answer 22

NSAIDs or intrarticular steroids

No available prophylaxis

Question 23

With what disease is polymyalgia rheumatica closely related?

Answer 23

Giant cell arteritis
20% of patients with PMR have GCA
50% of patients with GCA have PMR

Question 24

What are the characteristics of polymyalgia rheumatica?

Answer 24

Sudden onset of shoulder stiffness with possible pelvic girdle stiffness
Rare in under 50s and usually only affects over 70s
Affects females more than males (2:1)
ESR usually raised but no specific test
Systemic symptoms can include malaise, weight loss, fever and depression
Symptoms of giant cell arteritis can also be present

Question 25

What is diagnosis of polymyalgia rheumatica dependent on?

Answer 25

Compatible history
Aged >50
ESR >50
Dramatic response to steroids

Question 26

What is the full differential diagnosis associated with polymyalgia rheumatica?

Answer 26

• Myalgic onset Inflammatory joint disease
• Underlying malignancy
• e.g Multiple myeloma, lung cancer
• Inflammatory muscle disease
• Hypo/ hyperthyroidism
• Bilateral shoulder capsulitis
• Fibromyalgia

Question 27

How is polymyalgia rheumatica treated?

Answer 27

18-24 month course of 15mg daily prednisolone with appropriate bone prophylaxis

Question 28

What characteristic during treatment of polymyalgia rheumatica is more indicative of myalgic onset inflammatory joint disease?

Answer 28

Synovitis begins to present when tapering off steroids