OA31 Vitamin C deficiency presenting as juvenile idiopathic arthritis in an autistic child: a case study

Introduction Considered rare in the UK, we present a case of scurvy presenting as juvenile idiopathic arthritis (JIA). Scurvy is caused by vitamin C deficiency; the incidence is reported as 0.48 cases per 100,000 children under 16 years of age (2015–2017) in the UK. Scurvy is associated with gingival hypertrophy, petechiae, and musculoskeletal pain. The musculoskeletal manifestations and systemic features can present as JIA. This case highlights the importance of considering nutritional deficiencies in the differential diagnosis of paediatric patients presenting with symptoms similar to JIA to avoid misdiagnosis and ensure appropriate management. Case description A seven-year-old child with autism presented to the A/E with a week’s history of limping. Hip X-rays and blood tests were normal, so he was discharged. A week later, he returned with worsening symptoms, including swelling of the right knee. Blood tests and ultrasounds of bilateral hips and knees were normal, and he was once again discharged. On Day 14 of the illness, he was readmitted with increased right knee swelling and fever. Blood tests showed elevated inflammatory markers (ESR 26 mm/hr, CRP 33 mg/L). He was commenced on IV ceftriaxone for suspected osteomyelitis, but continued to experience low-grade fevers and developed swelling in the opposite knee, right ankle and mid-foot. On Day 22 of his illness, he was transferred to the Evelina and was found to have polyarthritis, reduced mobility, gingival hypertrophy and fever. Bloods revealed dropping counts, Hb 74 g/L, WBC 1.9 x 10^9/L and neutrophils 0.5 x 10^9/L, along with rising ferritin (96 -> 301 µg/L), dropping ESR (63 -> 17 mm/hr), and elevated LDH (428 U/L). Immunophenotyping and blood films were negative, leading to a provisional diagnosis of juvenile idiopathic arthritis (JIA) with evolving macrophage activation syndrome (MAS). He was started on anakinra and IV methylprednisolone. A full-body MRI revealed extensive metaphyseal signal abnormalities and mild soft-tissue oedema without active synovitis or joint effusion. The differentials included CRMO, lymphoproliferative disease, and scurvy. By this time, the lab Vitamin C level returned as extremely low at