Examqo › Examqo library › Internal medicine › Rheumatology · IMLE
Gout and pseudogout
Gout is diagnosed in joint fluid — needle-shaped, negatively birefringent crystals — flares are treated with colchicine, NSAIDs or steroids, and uric acid is lowered long term (allopurinol, target below 6 mg/dL) only when indicated, without stopping it during a flare.
Why it matters in the exam
A typical question presents a middle-aged man who woke with severe pain, swelling and redness of the big toe, sometimes after a heavy meal, alcohol or starting a diuretic. The candidate must know that the diagnostic test is joint aspiration — which also excludes septic arthritis — and that serum urate may be normal while the joint is inflamed. In pseudogout (CPPD) the crystals are rhomboid with weak positive birefringence, mainly in the knee and wrist, with cartilage calcification on the film; hyperparathyroidism, haemochromatosis and hypomagnesaemia should be sought.
Treatment questions test when to start urate lowering: there is a clear indication with a tophus, damage on the film or 2 or more flares a year. Allopurinol is started at a low dose (100 mg or less a day, less in kidney disease) and increased gradually to target, and low-dose colchicine is given in the first months to prevent flares. Before allopurinol, patients of Southeast Asian descent are tested for HLA-B*58:01 because of the risk of a severe skin reaction. An important interaction: allopurinol with azathioprine greatly raises azathioprine levels. Drugs that raise uric acid: thiazides, loop diuretics and low-dose aspirin.
Key points
- Diagnosis by aspiration: needles with negative birefringence = gout; rhomboid and weakly positive = CPPD.
- Flare: colchicine, NSAIDs or steroids within 24 hours.
- Urate lowering: tophus, damage on the film or 2 or more flares a year.
- Allopurinol from 100 mg or less, titrated to below 6 mg/dL, with preventive colchicine for 3–6 months.
- CPPD: knee and wrist; look for hyperparathyroidism, haemochromatosis and hypomagnesaemia.
Summary table
| Topic | Gout | Pseudogout (CPPD) | Exam note |
|---|---|---|---|
| Crystals | Needles, strong negative birefringence | Rhomboid, weak positive birefringence | Aspirate also to exclude infection |
| Typical joint | Big toe, ankle, knee | Knee, wrist | CPPD: cartilage calcification on the film |
| Flare treatment | Colchicine, NSAIDs or steroids within 24 hours | NSAIDs, colchicine, intra-articular steroid | Do not stop allopurinol during a flare |
| Urate lowering | Tophus, damage on the film, 2 or more flares a year | No crystal-lowering treatment | Allopurinol, target below 6 mg/dL (5 with tophi) |
| Associated conditions | Obesity, CKD, diuretics, alcohol | Hyperparathyroidism, haemochromatosis, hypomagnesaemia | CPPD in a young person → look for metabolic disease |
In the full version for subscribers
- A simple algorithm
- Memory aid
- Exam traps
- 5 review cards
- Enough for IMLE
The full version is open to subscribers of: Medical licensing exam (IMLE), Internal medicine, Family medicine, Geriatrics, Orthopedic surgery, Dermatology and venereology, Emergency medicine, Nuclear medicine, Occupational medicine, Diagnostic pathology, Diagnostic radiology, Urology, Vascular surgery.
Subscriber? Read the full topic Plans and prices 25 free questions
Sources
- American College of Rheumatology Guideline for the Management of Gout, 2020 — Indications for urate-lowering therapy, treat-to-target and flare management
- EULAR updated evidence-based recommendations for the management of gout, 2016 — Flare treatment and urate-lowering therapy
- Harrison's Principles of Internal Medicine, 21st edition (2022) — Gout and Other Crystal-Associated Arthropathies
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.