Crystal Arthropathies

Question 1

What is gout?

Answer 1

An inflammatory arthritis associated with hyperuricaemia and intra-articular sodium urate crystals.

Question 2

Which joint does gout most commonly affect?

Answer 2

MTP joint of big toe.

Question 3

Other common joints of gout.

Answer 3

Ankle

Foot

Small joints of the hand

Wrist

Elbow

Knees

It can also be polyarticular.

Question 4

Who are more commonly affected of gout, women or men?

Answer 4

Men 4:1 Women

Question 5

Risk factors of gout.

Answer 5

Hyperuricaemia

Male

Older age

Obesity

Diet with red meat high in purine

Alcohol (purine heavy + diuretic)

Medication like thiazides

Renal insufficiency

Post-menopausal females

Hypertension

Diabetes

Question 6

Causes of hyperuricaemia.

Answer 6

Impaired excretion of uric acid such as;
Chronic renal disease
Drugs therapy like thiazides
HTN
Lead toxicity
Primary hyperpara or hypothyroidism
Increased lactic acid production from alcohol, exercise or starvation

Increased production of uric acid

Increased turnover of purines such as;

Polycythaemia vera
Leukaemia
Carcinoma

Question 7

Clinical presentation of gout.

Answer 7

Acute onset of severe pain in an acute attack of gout.

Joint stiffness

Erythema and warmth.

The pain should be at its peak withing 24h and resolve within 2 weeks.

There can be swelling and tenderness of affected joint as well.

Gouty tophi can be present as well.

Question 8

Where might you see tophi?

Answer 8

Elbows

Knees

Achilles tendons

Dorsal aspects of hands and feet as well as pinna/helix of the ear.

Question 9

Differential diagnoses of gout.

Answer 9

Pseudogout

Septic arthritis

Cellulitis

RA

OA

Psoriatic arthritis

Sarcoidosis

Question 10

Investigations of gout.

Answer 10

1st line - Synovial fluid analysis to look for monosodium urate crystals.

Other investigations might be considered such as;

Serum uric acid levels (may be normal)

Ultrasound

X-ray of affected joint

Dual energy computed tomography.

Question 11

X-ray findings of gout.

Answer 11

Soft-tissue swelling in early stages

Well-defined punched out erosions seen in juxta-articular bone in late stages.

Lytic lesions in bone

The erosions can also have sclerotic borders with overhanging edges

Question 12

What will aspiration of synovial fluid show in gout?

Answer 12

Monosodium urate crystals

-ve bacterial growth

Negatively birefringent of polarised light

Needle shaped crystal

Question 13

Diagnostic criteria of gout.

Answer 13

1. Characteristic monosodium urate crystals in joint fluid, or

2. Characteristic monosodium urate crystals from tophus, or

3. Fulfilment of ≥6 of the following criteria:

> one attack of acute arthritis

Maximum inflammation developed within 1 day

Monoarthritis attack, redness observed over joints

First metatarsophalangeal joint painful or swollen

Unilateral first metatarsophalangeal joint attack

Unilateral tarsal joint attack

Tophus (confirmed or suspected)

Hyperuricaemia

Asymmetrical swelling within a joint on x-ray film

Subcortical cyst without erosions on x-ray film

Joint culture negative for organism during attack.

Question 14

Is joint pain and hyperuricaemia enough to diagnose gout?

Answer 14

No.

Also in an acute episode serum urate levels may go down.

Question 15

Non-pharma management of gout.

Answer 15

Reduce consumption of purine-rich foods.

Weight loss

Adequate hydration.

Question 16

What may precipitate an acute gout attack?

Answer 16

Excess food

Alcohol

Dehydration

Diuretic therapy

Question 17

Treatment of acute gout.

Answer 17

High dose NSAIDs + PPi

If this is contraindicated colchicine can be given 500 mcg BD.

If there is renal failure then NSAIDs and colchicine are both CId.

Steroids oral/IM/intra-articular can be given.

Rest and elevate joint, ice packs and bed cages can also be used.

Question 18

When to use prophylaxis of gout?

Answer 18

If 2 or more attacks in 12 months, tophi or renal stones.

CKD stage 2 or more

Question 19

Prevention medication of gout.

Answer 19

Allopurinol titrated from 100mg/24h increasing every 4 weeks until plasma urate < 0.3 mmol/L.

Allopurinol should not be started until acute attack is over.

Febuxostats can also be used if allopurinol is CId or not tolerated.

Uricosuric agents can also be given.

Question 20

What is pseudogout?

Answer 20

Calcium pyrophosphate dihydrate deposition arthropathy

There is deposition of calcium pyrophosphate dihydrate crystals in hyaline and fibrocartilage.

It is an acute monoarthropathy usually in larger joints in elderly.

It is usually spontaneous but can be provoked by illness, surgery or trauma.

It can be either acute or chronic.

Acute = monoarthropathy

Chronic = polyarthropathy that is symmetrical and very RA-like

Question 21

Risk factors of pseudogout.

Answer 21

Old age

Hyperparathyroidism

Haemochromatosis

Hypophosphataemia

Question 22

Investigations of pseudogout.

Answer 22

No bacterial growth

Calcium pyrophosphate crystals

Rhomboid shaped crystals

Positive birefringent of polarised light

X-ray

Serum calcium, urate, PTH, iron studies, magnesium, ALP

Question 23

Diagnostic criteria of pseudogout.

Answer 23

Demonstration of CPP crystals in tissues or synovial fluid by definitive means, such as x-ray diffraction or chemical analysis.

Question 24

Management of pseudogout.

Answer 24

Acute - Cool packs, rest, aspiration and intra-articular steroids.

NSAIDs + PPi +/- colchicine can prevent acute attacks.

Methotrexate and hydroxychloroquine may be consideed for chronic pseudogout.

Question 25

Metabolic causes of pseudogout.

Answer 25

Haemochromatosis

Hyperparathyroidism

Hypomagnesaemia

Question 26

X-ray changes in pseudogout.

Answer 26

Chondrocalcinosis is the classic xray change in pseudogout. It appears as a thin white line in the middle of the joint space caused by the calcium deposition. This is pathopneumonic (diagnostic) of pseudogout.