Seronegative Polyarticular Juvenile Idiopathic Arthritis: A Case Report.

Juvenile idiopathic arthritis (JIA) is a chronic rheumatologic childhood disorder of unknown etiology usually presenting with peripheral arthritis. Usually involving the small joints symmetrically, polyarticular JIA is characterized by involvement of 5 or more peripheral joints and is further categorized depending on RA Factor positivity. We aim to report a case of seronegative polyarticular JIA to increase awareness regarding this disease. A 15-year-old boy presented with 3-month history of bilateral symmetrical joint pains, swelling and morning stiffness lasting 3-4 hours. For his ankle and knee pain, he had consulted a local doctor who suspected Rheumatic Fever and started penicillin and analgesics resulting in minimal improvement. He was a student but was unable to attend school in last 2 months due to this illness and had become bed-bound for last 2 weeks. On examination, there was swelling and tenderness of ankles, knees, elbows, wrists, metacarpophalangeal and proximal interphalangeal joints bilaterally. On investigation, ESR, CRP and serum ferritin were raised with normal complete blood count, urinalysis, liver and renal function tests, ASO test, blood and urine cultures, TSH, serum CPK and serum aldolase. Echocardiography did not reveal any abnormalities. His ANA, RA factor and Anti-CCP antibodies were negative. He was diagnosed with Seronegative Polyarticular Juvenile Idiopathic Arthritis and started on oral prednisolone and methotrexate. Currently the patient is asymptomatic on methotrexate 20mg/week. Our patient with symmetrical polyarthritis had negative ANA, RA Factor and Anti-CCP antibodies leading to a diagnosis of seronegative polyarticular JIA. Early screening and prompt management of JIA is required to improve prognosis and reduce risk of disability. The differential diagnosis of childhood joint pains is wide and variable including diseases of autoimmune, cardiac and haematological systems. For diagnosis of JIA, arthritis persisting for more than 6 weeks with onset of symptoms prior to 16 years of age is required with exclusion of secondary causes of joint inflammation.   Keywords: Juvenile Idiopathic Arthritis, ANA, RA Factor, Anti-CCP antibodies, Methotrexate.