Demyelinating peripheral neuropathy has been described in association with tumor necrosis factor (TNF) inhibitors. It is rarely developed after treatment discontinuation. We present the case of a child with juvenile idiopathic arthritis who developed peripheral neuropathy few months after TNF inhibitor withdrawal with clinical worsening of the neurological sequelae while undergoing treatment with abatacept.

A fever of unknown origin (FUO) in children is usually described as a fever of at least 8 days duration with no apparent diagnosis after initial investigations, including taking medical history and preliminary laboratory assessment. Infectious diseases are the most common cause of FUO, followed by rheumatologic and neoplastic conditions. In this report, we present a case of a 15-year-old Caucasian boy with a silent past medical history, who presented at our Pediatric ER department with a three-day history of fever, fatigue, and abdominal pain with diarrhoea. Initial laboratory testing and microbiological work-up were non-significant. At hospital admission, a broad infectious diagnostic work-up was pursued, including serologies and polymerase-chain-reaction (PCR) for CMV, EBV, HAV, Parvovirus, Toxoplasma gondii and Adenovirus, all negative. Given mild splenomegaly and linfadenopathy, systemic Juvenile Idiopathic Arthritis (s-JIA) was suspected, as well as Multi-inflammatory Syndrome in Children (MIS-C), but the patient did not meet their main diagnostic criteria. Malignancy was ruled out by a negative bone marrow fine-needle aspiration cytology and whole-body PET-CT scan. On hospital day 8, Brucella was identified on a new set of blood cultures and a combined antibiotic therapy was started with IV Gentamicin plus per os Doxycycline. The patient’s general conditions rapidly improved, and both fever and diarrhoea resolved. A reassessment of the patient’s medical history before discharge revealed exposure to unpasteurized soft cheese in the weeks prior to the onset of symptoms. This case underlines the importance of taking a complete medical history, as well as a full diagnostic work-up to unveil unusual infectious etiologies behind FUO. After the preliminary negative microbiological tests, a connective tissue disease was ruled out (i.e. lack of cutaneous or articular involvement), as well as malignancy, which led to a closer evaluation for infection and the diagnosis of Brucellosis.

Background: Early-onset sarcoidosis is a rare systemic inflammatory granulomatous disease, distinguished by onset before the age of 4 and notably lacking pulmonary involvement. Unfortunately, the condition often shows clinical features similar to juvenile idiopathic arthritis, resulting in the misdiagnosis of numerous patients. This case report delves into the challenges associated with the delayed diagnosis of early-onset sarcoidosis, with a particular focus on the diagnostic methods employed to address this delayed recognition.Case presentation: A 15-year-old girl presented with a history of recurrent fever since infancy, accompanied by rash, arthritis, and joint deformity. Previously misdiagnosed with juvenile idiopathic arthritis, she underwent management with steroids and methotrexate, yielding no improvement. The diagnosis of early-onset sarcoidosis was made during adolescence based on serial examinations, comprehensive laboratory and radiological evaluations, and subsequent histopathology findings. Presently, the patient is receiving treatment with low-dose steroids and biologic therapy (Tocilizumab) and experiencing no disease progression.Conclusion: This case report underscores the importance of considering early-onset sarcoidosis in the differential diagnosis of pediatric patients exhibiting persistent arthritis from an early age. Early detection and treatment are crucial in averting complications and enhancing the overall quality of life.