Important differential diagnosis in acute tenosynovitis: BMJ
An 81-year-old male patient was admitted because of multiple cerebral ischaemic strokes. On day 2 of hospitalisation, he developed Pseudomonas aeruginosa sepsis, possibly secondary to a concomitant bladder infection. At day 3 of hospitalisation, tenderness of the right wrist with clinical signs of inflammation evolved. The peripheral intravenous access, localised distally of the radiocarpal joint, was initially suspected as the source of local infection.

Subsequent ultrasound examination of the wrist revealed signs of tenosynovitis of the extensor carpi ulnaris (ECU) tendon with tendon thickening and peritendinous effusion, while the radiocarpal joint revealed only grade 1 synovitis which did not explain the overall clinical appearance. In the absence of elevated serum urate levels, we suspected infectious tenosynovitis which might occur through haematogenous seeding or puncture wounds.

Tenosynovial fluid drawn by ultrasound-guided puncture of the ECU sheath revealed monosodium urate crystals on polarised light microscopy, and a diagnosis of gouty tenosynovitis was established. Injection with glucocorticosteroids into the tenosynovial sheath was performed and symptoms resolved after 3 days.

This clinical image demonstrates the diagnostic value of the examination of joints as well as tendons by ultrasound. Differential diagnosis of tenosynovitis of the wrist include rheumatoid arthritis, psoriatic arthritis, infectious tenosynovitis (may occur by haematogenous seeding or through puncture wounds) and calcium pyrophosphate dihydrate crystal deposition disease.

Learning points:-
• This case demonstrates that gout attacks can predominantly affect tendons, without major involvement of adjacent joints.

• In patients with infectious diseases and sonographic signs of tenosynovitis, centesis of the tenosynovial sheath and microscopic examination for crystals should be performed as gout flares can lead to tenosynovitis and mimic infectious tenosynovitis.

• Gout attacks may manifest as tenosynovitis without involvement of adjacent joints

• Centesis of the tenosynovial sheath and microscopic examination should be encouraged in acute tenosynovitis as gout flares may mimic infectious tenosynovitis