A 35-year-old man is seen in the emergency department because he has developed a painful, swollen right knee. This has occurred rapidly over the past 36h. There is no history of trauma to the knee or previous joint problems. He feels generally unwell and has also noticed his eyes are sore. He has had no significant previous medical illnesses. He is married with two children. He is a non-smoker and drinks about 15 units of alcohol per week. He is a businessman and returned 3 weeks ago from a business trip to Thailand.
Examination His temperature is 38.0°C. Both eyes appear red. There is a brown macular rash on his palms and soles. Examination of cardiovascular, respiratory, abdominal and neurological systems is normal. His right knee is swollen, hot and tender with limitation in flexion. No other joint appears to be affected.
Normal Haemoglobin 13.8g/dL 13.3–17.7g/dL Mean corpuscular volume (MCV) 87fL 80–99fL White cell count 13.6 109/L 3.9–10.6 109/L Platelets 345 109/L 150–440 109/L Erythrocyte sedimentation rate (ESR) 64mm/h 10mm/h Sodium 139mmol/L 135–145mmol/L Potassium 4.1mmol/L 3.5–5.0mmol/L Urea 5.2mmol/L 2.5–6.7mmol/L Creatinine 94amol/L 70–120amol/L
Urinalysis: no protein; no blood; no glucose Blood cultures: negative X-ray of the knee: soft-tissue swelling around joint
INVESTIGATIONS
Questions • What is the diagnosis and what are the major differential diagnoses? • How would you investigate and manage this patient?
ANSWER
This patient has a monoarthropathy, a rash and red eyes. Investigations show a raised white cell count and ESR. The diagnosis in this man was postinfective inflammatory mucositis and arthritis, often shortened to reactive arthritis, and also known as Reiter’s syndrome. However there is now a move to disassociate the name of Reiter (1881–1969) from this disease in view of his crimes committed, as a doctor, by experimenting on prisoners in the concentration camps of Nazi Germany. This disease classically presents with a triad of symptoms (although all three may not always be present): • seronegative arthritis affecting mainly lower limb joints • conjunctivitis • non-specific urethritis. The trigger can be non-gonococcal urethritis (NGU) or certain bowel infections. This patient is likely to have contracted NGU after sexual intercourse in Thailand. On direct questioning he admitted to the presence of a urethral discharge. The acute arthritis is typically a monoarthritis but can develop into a chronic relapsing destructive arthritis affecting the knees and feet, and causing a sacroiliitis and spondylitis. Tendinitis and plantar fasciitis may occur. The red eyes are due to conjunctivitis and anterior uveitis, and can recur with flares of the arthritis. The rash on the patient’s palmar surfaces is the characteristic brown macular rash of this condition – keratoderma blenorrhagica. Other features of this condition that are sometimes seen include nail dystrophy and a circinate balanitis. Systemic manifestations such as pericarditis, pleuritis, fever and lymphadenopathy may occur in this disease. The ESR is usually elevated.