Crystal arthropathies

Question 1

Two main conditions

Answer 1

Gout and pseudogout.

Question 2

What is gout?

Answer 2

Inflammatory arthritis associated with monosodium urate crystal depositation in the joint.

Question 3

Aetiology of gout

Answer 3

More common in men.

Prevalence increases with age.

Question 4

Pathogenesis of gout

Answer 4

Uric acid is the final compound in the breakdown of purines in DNA metabolism (adenine & guanine). Hyperuricaemia may be due to renal underexcretion (which can be exacerbated by diuretics or renal failure) or due to excessive intake of alcohol, red meat and seafood

Question 5

Hyperuricaemia

Answer 5

Uric acid level of greater than 7mg/dL (0.42mmol.L

Question 6

Causes of uric acid underexcretion

Answer 6

Renal insufficiency
Starvation
Dehydration
Hypothyroidism
Hyperparathyrodism
Drugs (diuretics, levodopa, cyclosporin A, pyrazinamide)
Alcohol abuse

Question 7

Causes of uric acid overproduction

Answer 7

Could be genetic e.g. Lesch Nyhan
Could be due to high cell turnover e.g. psoriasis
Dietary- e.g. red meat, seafood, alcohol.

Question 8

Diagnosis of gout

Answer 8

Diagnosis of gout is based on identification of crystals or classic radiographic findings, not hyperuricemia alone

Question 9

Clinical presentation of gout

Answer 9

Rapid onset (hours, often overnight)
Red, hot joint
Severe pain
Duration- up to 2 weeks
Site- 
1st MTPJ>ankle>knee> upper limb joints>spine

Question 10

Differential diagnosis of gout

Answer 10

Septic arthritis
Trauma
Seronegative arthritis

Question 11

Chronic polyarticular gout

Answer 11

Chronic joint inflammation
Usually after having recurrent acute attacks > 10 years 
Often diuretic associated
High serum uric acid
Tophi
May get acute attacks

Question 12

Investigations into gout

Answer 12

JOINT ASPIRATION
Inflammatory markers( CRP, PV/ESR)-raised
WCC may be raised ( difficult to differentiate from infection)
X ray: 
normal in acute attack
chronic/repeated attacks- 
erosions,  overhanging osteophytes, 
joint destruction

Question 13

Management of gout in acute attacks

Answer 13

NSAIDs ( if no contraindication) 
or 
Colchine
or 
corticosteroids.

Question 14

Long term management of gout

Answer 14

Allopurinol. 
start 2-4 weeks after acute attack
-Start low dose and titrate
-Aim for target serum urate <0.30mmol/L 
(British Society of Rheumatology guidelines

Question 15

Lifestyle modifications needed in gout

Answer 15

Restrict red meat, offal, beans, shellfish
Reduce Alcohol ( 3 alcohol free days/ week, but still overall keep within limits)
Lose weight
Fluids- 2L /day ( not fizzy drinks with fructose!)

Question 16

Pseudogout/Calcium Pyrophosphate Dihydrate Deposition Disease (CPPD)

Answer 16

More common in elderly
Chondrocalcinosis increases with age
Related to osteoarthritis
Affects fibrocartilage - knees, wrists, ankles

Question 17

What shape are psuedogout crystals

Answer 17

Rhomboid/envelope shaped crystals

Weakly positive birefringence

Question 18

What shape are gout crystals

Answer 18

Needle shaped- negatively birefringence.

Question 19

Pseudogout/Calcium Pyrophosphate Dihydrate Deposition Disease (CPPD) associations

Answer 19

Aging
Hyperparathyroidsim
Familial hypocalciuric
     hypercalcaemia
Haemochromatosis
Haemosiderosis
Hypophosphatasia

Question 20

Treatment of psuedogout

Answer 20

NSAIDS
Colchicine
Steroids
Rehydration

Question 21

Hydroxyapatite

Answer 21

“Milwaukee shoulder”
Hydroxyapatite crystal deposition in or around the joint.
Acute and rapid deterioration.
Females, 50-60 years
Crystals not detected under light or polarised microscopy- Alizarin stain show red clumps