Image of “The Gout”, by James Gillray. Wikimedia Commons, CC BY

Natural History of Gout

1. Asymptomatic hyperuricemia
2. Asymptomatic MSU crystal deposition (without gout)
3. Recurrent gout flares with intercritical gout
4. Gout with chronic gouty arthritis/tophaceous gout/erosive gout
   

Risk factors

3 clinical classical stages

1. Gout flare – acute arthritis induced by MSU crystals
2. Intercritial gout – asymptomatic period after or between gout flare
3. Chronic gouty arthritis +/- tophi – joint deformity e.g. fixed flexion deformity

• 1st presentation of acute gout: typically acute monoarthritis of the 1st MTP joint (podagra), midfoot or ankle. Less commonly with oligoarthritis; Self-limiting, lasting about 1 – 2 weeks.
• If hyperuricemia persist –> recurrent flares –> polyarticular gout (including those of upper limb)
• Common sites of tophi: 1st MTP joint, Achilles tendon, peroneal tendon, helix of the ear, olecranon bursa & finger pad.

Extra-articular manifestation: Urolithiasis, Chronic nephropathy (Thus, don’t forget to assess also patient’s Renal Function)

Diagnosis 🔬

Definite (gold standard): Demonstration of MSU (negative birefringent crystals) in synovial fluid or tophus.
Often time, this may not be possible, thus diagnosis can be made from clinical presentation, lab investigations & imaging modalities.

Laboratory investigations

Mainly serum uric acid (SU)
– Cut-off level to diagnose hyperuricemia: > 6.8 mg/dL (408 umol/L; 0.408 mmol/L) at physiological pH & body temperature.

Keep in mind that:
– Diagnosis of gout should not be made based on hyperuricemia alone.
– A normal/low SU during flare does not exclude gout as level may be normal during flare. If clinical suspicion is high, SU may be repeated 2 weeks or more after complete resolution of flare.

Imaging modalities

X-ray & ultrasound
Typical radiographic features of gout on plain radiograph:
– Bone erosions with overhanging edges and a sclerotic rim (“punched out”/”rat bite” erosions)
– Bony proliferation
– Joint space are generally preserved until late stages of the disease
– No peri-articular osteopenia
– Soft tissue tophi +/- calcification

ACR/EULAR gout classification criteria

Utilizes laboratory, imaging and clinical criteria to aid in diagnosis
Score of >= 8 can be classified as having gout
Accessible via: https://goutclassificationcalculator.auckland.ac.nz/

Co-morbidities

Gout is an independent risk factor for mortality due to coronary heart disease & kidney disease.
Screening for comorbidities e.g. HTN, DM, Dyslipidemia, CHD, & renal disease including urolithiasis should be done upon diagnosis & during follow up.
Below are the suggested baseline investigations which include screening for comorbidities as given in our Malaysia CPG guidelines.

Differential diagnosis

1. Septic arthritis
   – Commonly involves knee joint (other sites: hip, shoulder, ankle, wrist)
   systemic features e.g. fever, ill or septic-looking
   – Risk factors e.g. concomitant bacteria infection, recent intra-articular injection
   – Leucocytosis and increased CRP
   
2. Acute calcium pyrophosphate crystal arthritis
   – Age > 60 y/o
   – Involvement of a degenerative joint
   – Plain radiograph: chondrocalcinosis
   
3. Psoriatic arthritis
   
4. Reactive arthritis
   – Recent genitourinary or GI infection.
   – Presence of urethral discharge or ulcer, rash on soles, conjunctivitis.