Just a painful swelling of the ankles?

A 41 year old man presented with a three week history of acute painful swelling of both ankles accompanied by local erythema and heat, morning stiffness of short duration, and fever. During the fourth week, a tender nodular erythematous eruption developed in both legs, suggestive of erythema nodosum. The man had no personal, family, or epidemiological medical history. He reported no previous infections, trauma, or new medications. On physical examination, his temperature was 38.2°C. There was erythema, oedema, pain, and heat in both ankles, with a normal range of movement in the ankle joints, and lesions compatible with erythema nodosum on the anterior aspect of both legs.

Laboratory results showed

• Leucocytosis of 14.5×10⁹/L (reference range 4-10) with neutrophilia

• Erythrocyte sedimentation rate of 56 mm in first hour (1-20)

• C reactive protein 9.53 mg/dl (<0.5)

• Normal results on tests of renal, liver, and thyroid function

• Normal levels of calcium (serum and urinary); 1,25-dihydroxyvitamin-D, and angiotensin converting enzyme

• Negative blood and urine cultures, viral serology (Epstein-Barr, cytomegalovirus, HIV, hepatitis, parvovirus-B19), interferon-gamma-release-assay, and negative autoantibody test results

• Chest radiography showed mild bilateral hilar lymphadenopathy (fig 1). A chest computed tomography scan and 18F-FDG-PET/computed tomography scan confirmed symmetrical bilateral hilar lymphadenopathy, with no other findings. Ankle ultrasound showed bilateral peri-articular soft tissue oedema, without synovitis or tenosynovitis.

• Bronchoalveolar lavage fluid contained 45% lymphocytes, 11.1 CD4/CD8 cell ratio, and negative bacteriological examination. Bronchial aspiration showed polymorphonuclear cells. Pulmonary function tests were normal.