Crystal Arthopathy

Question 1

What are crystal arthropathies? What are some of the commonly implicated minerals?

Answer 1

A class of diseases characterized by the deposition of mineralized material within joints and peri-articular tissue

Monosodium urate - gout
Calcium pyrophosphate dihydrate (CPPD) - pseudogout
Basic calcium hydroxyapatite (BCP) - calcific periarthritis / tendonitis

Question 2

Where do the minerals causing crystal arthopathies come from?

Answer 2

From the metabolism of purines (endogenous and food)

Purines -> Hypoxanthine & Xanthine -> Uric Acid

Question 3

Where is uric acid excreted? What is the most common cause of hyperuricaemia?

Answer 3

70& in the kidneys and 30% in biliary tract

Reduced renal clearance

Question 4

What are the two main mechanisms of hyperuraemia occurrence?

Answer 4

Overproduction of uric acid - diseases with high cell turnover
- Malignancies, severe exfoliative psoriasis, ethanol, cytotoxic drugs

Under-excretion of uric acid
- renal impairment, hypertension, hypothyroidism, booze**, diuretics, exercise, starvation, dehydration, lead poisoning

Question 5

Describe the pathophysiology of Lesch Nyan Syndrome. What conditions can it cause?

Answer 5

HGPRT deficiency, enzyme responsible for recycling purines. In it’s absence the body makes more purines to keep levels up, leads to hyperuraemia & gout

• Gout, renal disease

Question 6

What are some risk factors for gout?

Answer 6

• Old age, being male, high BMI
• Booze, antiduiretics,
• Dehydration
• High purine intake

Question 7

What is gout? Where does it usually occur?

Answer 7

A form of arthritis caused by excess uric acid in the bloodstream

First MTP joint (foot)

Question 8

What is the progression of gout usually like? How long does it last?

Answer 8

Patient goes to bed feeling a bit of a “niggle” abnormality in their foot

Wake up in the morning with swelling and severe pain around the joint

Typical episode lasts 5-7 days

Question 9

Symptoms / signs of gout?

Answer 9

• Monoarthritis with severe pain
• Erythema & heat over joint
• Swelling
• If chronic: tophi - depositions of uric acid, occur over bony joints like hands, elbow, foot, ear

Question 10

Investigation of suspected gout?

Answer 10

• Aspiration of joint to look for crystals

Question 11

Management of acute exacerbations of gout?

Answer 11

• NSAIDs
• Colchicine (anti-inflammatory)
• Steroids: IA, IM, oral

Question 12

When is prophylactic treatment needed after a single attack of gout?

Answer 12

• 1st attack treated if: polyarticular gout, tophaceous gout, urate calculi, renal insufficiency
• Don’t start prophylactic treatment when acute attack is still underway
• If 2 attacks of gout in 1 year begin prophylactic treatment

Question 13

Treatment for lowering of hyperuricaemia? (prophylactic gout treatment)

Answer 13

• Xanthine oxidase inhibitor (allopurinol)**
• Febuxostat (also xanthine oxidase inh) (Cx in CVS disease)
• Uricosuric agents (enhance excretion of uric acid)
• Canakinumab (biologic)

Question 14

Who tends to get pseudogout? Where does it tend to occur? Investigations?

Answer 14

• Elderly females. Often occurs post-infection
• Tends to occur at the knee
• Aspirate the joint for crystals / look for chondroalcinosis on x-ray

Question 15

Management of pseudogout?

Answer 15

• NSAIDs
• IA steroids
• Colchicine

Question 16

What condition is closely linked with polymyalgia rheumatica?

Answer 16

Giant cell arteritis

• 20% of patients with PMR have GCA
• 50% of patients with GCA have PMR

Question 17

Who tends to get polymyalgia rheumatica?

Answer 17

• The elderly (70+)

- F > M

Question 18

What are the symptoms / signs of polymyalgia rheumatica?

Answer 18

• Sudden onset shoulder +/- pelvic girdle stiffness
• Systemic features: weight loss, fever, depression
• Occasionally arthralgia / synovitis
• Muscle power normal

Question 19

Investigations for polymyalgia rheumatica?

Answer 19

Bloods:

• Raised ESR (>45 often 100)
• Anaemia
• If suspected give patients steroids, should see dramatic response if polymayalgia rheumatica

Question 20

Treatment of polymyalgia rheumatica?

Answer 20

Low-dose corticosteroids (prednisolone) - 18-24 month course

• Should have a rapid response
• Bone prophylaxis if risk group for osteoporosis (or refer to DXA scan)