Crystal Arthropathy

Question 1

What are crystal deposition diseases characterised by?

Answer 1

Characterised by deposition of mineralised material within joints and peri-articular tissue

Question 2

Which crystal is implicated in gout?

Answer 2

Monosodium urate

Question 3

Which crystal is implicated in pseudogout?

Answer 3

Calcium pyrophosphate dehydrate (CPPD)

Question 4

Which crystal is implicated in calcific periarthritis/tendonitis?

Answer 4

Basic calcium phosphate hydroxyl-apatitie (BCP)

Question 5

How does gout present?

Answer 5

• Typically affects 1st MTP
• Occurs overnight: usually a niggle going to bed
• Extremely painful
• Red shiny overlying skin: may peel
• Chalky white spots of crystal deposits

Question 6

Where does urate in the body come from?

Answer 6

• Endogenous production of uric acid by degradation of purines = 2/3
• Dietary = 1/3

Question 7

What happens to uric acid in the body?

Answer 7

• 70% excreted by the kidney

- Remained eliminated into the biliary tract and converted to allantoin by colonic bacterical uricase

Question 8

Why does hyperuricaemia occur in gout?

Answer 8

Results from reduced efficiency of renal urate clearance

Question 9

What are the 2 mechanisms of hyperuricaemia?

Answer 9

• Overproduction

- Under excretion

Question 10

What can cause overproduction of uric acid?

Answer 10

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

Question 11

What can cause under excretion of uric acid?

Answer 11

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

Question 12

What happens once there is saturation of uric acid in the body?

Answer 12

Crystals begin to form. Crystals irritate the synovium causing inflammation leading to an inflammatory response

Question 13

What is Lesch Nyan syndrome caused by?

Answer 13

HGPRT deficiency

Question 14

What are the features of Lesch Nyan syndrome?

Answer 14

• X-linked recessive
• Intellectual disability
• Aggressive and impulsive behaviour
• Self mutilation
• Gout
• Renal disease

Question 15

What are the risk factors for gout?

Answer 15

• Obesity
• Hypertension
• Hypercholesterolemia
• Diabetes mellitus
• Alcohol
• Diuretics
• Dehydration

Question 16

What is the prevalence of gout in the UK?

Answer 16

• Predominantly a disease of older men

- Gout is rare in young women due to the effect of oestrogen

Question 17

How is gout diagnosed?

Answer 17

History

• Classical
• Episodic in nature

Examination
Differential

Investigations: Aspiration (looking for crystals, exclude infection)

• Sent for gram stain and culture
• Polarising microscopy

Question 18

How should an acute flare of gout be treated?

Answer 18

• NSAIDs
• Colchine
• Steroids (IA, IM, oral)

Question 19

When is hyperuricaemia treated?

Answer 19

1st attach not treated unless

• Single attack of polyarticular gout
• Tophaceous gout
• Urate calculi
• Renal insufficiency

Treat if 2nd attack within 1 year

Prophylactically prior to treating certain malignancies

DO NOT treat asymptomatic hyperuricaemia

Question 20

How can uric acid be lowered?

Answer 20

• Xanthine oxidase inhibitor e.g. Allopurinol
• Febuxostat
• Uricosuric agents e.g. sulphinpyrazone, probenecid, benzbromarone
• Canakinumab (IL1 anatagonist)

Question 21

What are the rules for lowering uric acid levels?

Answer 21

-Wait until 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

Question 22

How does pseudogout present?

Answer 22

• Usually affects elderly women
• Erratic flares
• Can be idiopathic, familial or metabolic
• Triggered by trauma or intercurrent illness
• Usually quick onset and settles within a week

Question 23

How is pseudogout managed?

Answer 23

• NSAIDs
• I/A steroids
• No prophylactic therapies
• Rest and splinting to make patient comfortable

Question 24

What is polymyalgia rheumatica?

Answer 24

Inflammatory condition of the elderly with a close relationship with GCA (most common of the systemic vasculitides characterised by involvement of the large vessels

Question 25

What is the cycle of polymyalgia rheumatica?

Answer 25

• Polymyalgia rheumatica
• Giant cell arteritis
• High ESR and anaemia

Question 26

How does polymyalgia rheumatica present?

Answer 26

• F:M 2:1
• Usually >70 years
• Sudden onset of shoulder +/- pelvic girdle stiffness
• ESR >45 often 100
• Anaemia
• Malaise, weight loss, fever, depression
• Can get arthralgia/synovitis occasionally

Question 27

How is a diagnosis of polymyalgia rheumatica made?

Answer 27

• Compatible history
• Age >50
• ESR>50
• Dramatic steroid response
• No specific diagnostic test

Question 28

What is the differential diagnosis for polymyalgia rheumatica?

Answer 28

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

Question 29

How is polymyalgia rheumatica treated?

Answer 29

• Prednisolone 15mg per day initially
• 18-24 mth course
• Bone prophylaxis