Bilateral leg swelling as the presenting symptom of Löfgren syndrome in a paediatric patient: a rare presentation of a rare paediatric disease.

A 17-year-old previously healthy man presented with a 4-week history of progressive bilateral leg swelling with discomfort and erythema, but no signs of arthritis or erythema nodosum. An incidental finding of a query pulmonary nodule on chest X-ray prompted chest CT for further evaluation, revealing bilateral hilar and mediastinal lymphadenopathy. The patient then underwent endobronchial ultrasound and transbronchial needle aspiration biopsies of mediastinal lymph nodes. Biopsies and bronchoalveolar lavage samples were negative for microbiology, including mycobacterial culture. Pathology demonstrated non-caseating granulomas consistent with a diagnosis of sarcoidosis. Weeks later, he developed arthralgias of the left metacarpophalangeal joints and erythema nodosum and was diagnosed with Löfgren syndrome, a phenomenon rarely described in the paediatric population. This case highlights an approach to lower extremity swelling as well as hilar lymphadenopathy in the paediatric population. In addition, it emphasises the importance of multidisciplinary teamwork for accurate and timely diagnoses.