P3.M241: A Case of Juvenile Mixed Connective Tissue Disorder(MCTD) in a Young Female: A Wolf in Sheep's Clothing.

Introduction: Juvenile mixed connective tissue disease (JMCTD) is a highly uncommon autoimmune disorder comprising concurrent symptoms of juvenile idiopathic arthritis, polymyositis, cutaneous scleroderma, systemic lupus erythematosus, and systemic sclerosis. It has a highly variable presentation, making it a challenging diagnosis.

Case Description: An 11-year-old female presented with a three-month history of persistent bilateral cervical lymphadenopathy along with intermittent low-grade fevers and loss of appetite, leading to significant weight loss. On further interrogation, she also complained of hair fall, dysphagia, dryness of eyes and mouth, and bilateral knee pain. She was hemodynamically stable on admission, and a physical exam revealed multiple tender, mobile cervical nodes(Figure1), restrictive movement of the knees and small joints of both hands, intermittent bluish discoloration of both palms and fingers on exposure to cold, and swelling of fingers with stretched shiny skin (Figure2). Blood work showed elevated erythrocyte sedimentation rate, C-reactive protein levels, serum ferritin, and pancytopenia. Cardiac echocardiography revealed mild pericardial effusion. The initial working diagnosis included tuberculous lymphadenitis, but there was no resolution of symptoms on completing three months of anti-tuberculous treatment. Given continued symptoms, further diagnostic evaluations, including repeated biopsies of the bilateral cervical lymph nodes, showed reactive lymphadenitis. Bone marrow biopsy was unremarkable. An exhaustive investigation of infectious etiologies, including blood cultures, was negative. Subsequent serological tests were positive for rheumatoid arthritis, strongly positive for antinuclear antibodies (ANA) with a speckled pattern, positive for anti-U1RNP (antibody to U1-ribonucleoprotein) and anti-Smith antibodies (anti-Sm ab), and negative for anti-cyclic citrullinated peptide (CCP) antibodies. These findings and clinical presentation established a diagnosis of JMCTD. Initial treatment consisted of methotrexate, prednisone, chloroquine, and non-steroidal anti-inflammatory drugs (NSAIDs).

Discussion: JMCTD has a heterogeneous presentation and can mimic various rheumatological, infectious, and malignant pathologies, hence posing a considerable diagnostic challenge. Diagnosis is confirmed with symptoms and serologic testing positive for ANA and anti-U1-RNP positive. A detailed organ system screening including chest x-ray, pulmonary function test, electrocardiogram, and echocardiogram should be performed. Treatment is based on the severity of symptoms and variability of response, including immunosuppressants, mainly low-dose corticosteroids, NSAIDs, and hydroxychloroquine. Long-term sequelae include renal involvement, restrictive lung disease, pulmonary hypertension, loss of joint function, and oesophageal dysmotility. The absence of standardized classification makes identifying JMCTD cases difficult, and limited data is available for evidence-based management. To tackle these challenges and enhance our understanding of the management of this complex rheumatic disease in children, a multidisciplinary approach that fosters collaboration among researchers, clinicians, and patients is essential.

Conclusion: It is imperative to have a high clinical suspicion in children especially adolescent girls presenting with prolonged pyrexia and lymphadenopathy and to prevent multisystemic complications. Early referral to a pediatric rheumatologist is of paramount importance.