We present a six-year-old girl who consulted the health centre for right-sided gonalgia with no inflammatory signs or history of trauma. She was treated with ibuprofen and three months later returned to the clinic with pain and inflammation of the fifth metatarsal of the right foot, of a progressive nature, which limited her ambulation. Subsequently, pain and swelling appeared on the dorsum of the right hand. None of the symptoms were accompanied by previous influenza, gastrointestinal infection or urinary symptoms, and she was afebrile at all times. One week later, she visited the clinic for persistent symptoms and functional impotence to stand upright.
Her personal and family history and pregnancy were of no clinical interest. Her psychomotor development was normal. The patient's weight was 23.5 kg, height 122 cm, heart rate 74 bpm and general condition was acceptable. Examination revealed right knee with pain, swelling and limited flexion mobility due to pain at 90°, patellar balling and mild swelling with pain in the fifth metacarpophalangeal joint of the right hand, and right foot with increased sensitivity to pressure at the base of the fifth metatarsal and local swelling with pain, without deformity or crepitus. No vasculonervous deficit. The physical examination was normal, with no rash, lymphadenopathy or visceromegaly. X-rays were normal at all times.
Laboratory tests: mild thrombocytosis (425 000/µl), no leukocytosis or neutrophilia, C-reactive protein 13 mg/ml, erythrocyte sedimentation rate 52, antinuclear antibodies (ANA) positive at 1/160, rheumatoid factor negative, anti-DNA negative.
Arthrocentesis was performed (biochemistry and culture) obtaining inflammatory fluid with 5360 cells/ml, glucose 69 mg/dl, protein 5.4 g/dl and negative culture.
Treatment was started with ibuprofen at a dose of 200 mg every eight hours, pending assessment by the specialist, with a slight improvement. Paediatric Rheumatology requested an assessment, which extended the blood tests, performed an ophthalmological study and started treatment with deflazacort. The extended laboratory tests were negative for anti-cyclic citrullinated peptide antibodies, ENA, HLA B27 and hepatitis B and C serology. Thyroid, urinalysis and coagulation tests were also normal.
One month later, she was reviewed by Paediatric Rheumatology and was diagnosed with right knee arthritis ANA(+) and probable JIA, due to persistent swelling and pain in the right knee and tarsus. The study was completed with foot ultrasound and corticosteroid infiltration. The ultrasound was normal and the patient progressed well after the infiltration.