Crystal Arthropathy

Question 1

Presentation of gout

Answer 1

1st MTP most common (can be around other joints)
Swelling and redness over joint
Very painful sudden onset in morning
Untreated lasts 7-10 days before settling

Question 2

What are tophi

Answer 2

Massive accumulations of uric acid found on bony prominences, form if persistently high levels of uric acid and gout

Question 3

How is purine related to gout

Answer 3

Purine (2/3 from DNA breakdown, rest from diet) is broken down into urate which is mostly excreted in the kidney and rest from biliary tract by colonic bacterial uricase to allantoin.

Question 4

How do high levels of urate cause gout

Answer 4

If too much rate is made and not enough excreted plasma urate levels rise and crystals form around joints - it becomes acute gout when it builds up and breaks through the joint, irritating the synovium and becoming symptomatic

Question 5

What is usually the cause of hyperuricaemia

Answer 5

Decreased efficiency of renal urate excretion

Question 6

Hyperuricaemia causes

Answer 6

Overproduction

• malignancy (lymphoproliferative, tumour lysis syndrome)
• Severe exfoliative psoriasis
• Drugs (ethanol, cytotoxic drugs)
• Inborn errors of metabolism
• HGPRT deficiency

Underproduction

• Renal impairment
• HTN
• Hypothyroidism
• Drugs - alcohol, low dose aspirin, diuretics, cyclosporin
• Exercise, starvation, dehydration
• Lead poisoning

Question 7

How is alcohol related to gout

Answer 7

Alcohols are rich in purines (i.e. beer contains guanine) and ethanol –> acetyl CoA which leads to adenine nucleoside degeneration resulting in increased adenosine monophosphate formation (precursor of uric acid)
Alcohol also increases lactic acid level in the blood leading to inhibition of uric acid excretion

Question 8

What is Lesch Nyan syndrome

Answer 8

HGPRT deficiency, x-linked recessive intellectual disability causing:

• aggressive and impulsive behaviour
• self-mutilation
• gout
• renal impairment

Question 9

What does HGPRT do

Answer 9

Role in recycling of purine bases

Without it they are excreted as uric acid

Question 10

Triggers of gout

Answer 10

Obesity 
Alcohol 
Increased cholesterol and BP 
Diuretics 
Dehydration

Question 11

Which sex does gout usually affect and why

Answer 11

Males - they have higher urate levels and oestrogen has a uricosuric effect

Question 12

Why is ageing a risk factor for gout

Answer 12

• Increased sUA mainly due to reduced renal function
• Increased diuretic use and drugs which increase sUA
• Age-related connective tissue changes which can encourage crystal formation

Question 13

Diagnosis of gout

Answer 13

Hx and Exam - 1st MTP (obviously gout), Knees and ankles (could be a septic joint)
Investigations
- Aspiration (see crystals and exclude infection)
- Gram stain and culture (infection)
- Polarising Microscopy (crystals)

Question 14

What is the main crystal seen in gout

Answer 14

monosodium urate

Question 15

Management of acute flare of gout

Answer 15

NSAIDs
Colchicine (can cause diarrhoea and takes longer to work)
Steroids (IA, IM, oral) - 2nd line

Question 16

When to treat hyperuricaemia

Answer 16

If 2 symptomatic attacks in 1 year
Prophylactically prior to treating certain malignancies 
1st attack if:
- single attack of polyarticular gout 
- tophaceous gout 
- urate calculi 
- renal insufficiency 

Wait until acute attack has settled before trying to reduce urate levels with allopurinol as can trigger an attack of gout

Question 17

Treatment of hyperuricaemia

Answer 17

Allopurinol (xanthine oxidase inhibitor) - 1st line
Febuxostat (same as above but metabolised by liver instead of kidney)

Uricosuric agents (sulphinpyrazone, probenecid) - 2nd line

Address lifestyle factors
- HTN, smoking, fizzy drinks, alcohol, obesity, purine rich foods, dehydration, more F&V (cherries), yoghurt

Question 18

Presentation of pseudogout

Answer 18

Affects knee
Mainly in elderly females
Triggered by trauma or intercurrent illness

Question 19

What crystal is commonly found in pseudo gout

Answer 19

Calcium pyrophosphate dihydrate (CPPD)

Question 20

Investigations for pseudo gout

Answer 20

X-ray - if trauma in person with acutely swollen joint, shows chondrocalcinosis commonly in knee and wrist

Aspiration - shows pyrophosphate crystals on microscopy (rhomboid shape, positively birefringent)

Question 21

Management of pseudo gout

Answer 21

NSAIDs
IA steroids (if confident of no infection)
Rest, Splinting, analgesia

Question 22

What is polymyalgia rheumatica

Answer 22

Inflammatory condition of elderly (females>males)

Question 23

Presentation of polymyalgia rheumatica

Answer 23

SUDDEN onset STIFFNESS of shoulder / pelvic girdle
Malaise, weight loss, fever, depression
Arthralgia, synovitis occasionally

Question 24

What is polymyalgia rheumatic associated with

Answer 24

GCA
- 20% with PMR may have GCA
- 50% with GCA may have PMR
High ESR, anaemia

Question 25

Diagnosis of polymyalgia rheumatica

Answer 25

By history

• Age >50
• ESR >50
• Dramatic steroid response within ~24-48hours

Question 26

Treatment of PMR

Answer 26

Prednisolone 15mg per day for 18-24 months

Bone prophylaxis as on long term steroids (bone loss greatest in 1st 3 months of onset of steroids) - do DEXA scan

Question 27

Differential diagnosis of PMR

Answer 27

Myalgic onset inflammatory joint disease
Malignancy (multiple myeloma, lung cancer)
Hypo and Hyperthyroidism (check TFTs)
Inflammatory muscle disease (check creatinine)
Bilateral Shoulder Capsulitis (Frozen shoulder) - more mechanical pain
Fibromyalgia