P49 Two cases of persistent isolated motor mononeuropathy secondary to etanercept in paediatric population

Abstract Background Juvenile idiopathic arthritis (JIA) is the most common form of inflammatory arthritis in children and has an annual incidence of 33 per 100,000. With the introduction of biologic therapies, the goal of disease remission, both on and off treatment, is becoming increasingly achievable. Etanercept, a TNF-α inhibitor, was the first biologic to be used in JIA and is currently recommended as an add-on therapy in patients with inadequate response to methotrexate alone. While it is generally considered to have a good safety profile, a number of adverse events have been documented, including neuropathy. Methods We present two cases of etanercept related mononeuropathy, which persisted despite intravenous immunoglobulin (IVIG) therapy. Results Case 1: A 12 year-old girl with polyarticular JIA, who had commenced on etanercept 2 years previously, presented with an acute inability to fully flex her right index finger, associated with intermittent paraesthesia over the area. On examination, there was weakness in the deep flexor digit II and she was unable to flex at the distal interphalangeal joint. Deep tendon reflexes and sensation were normal. Nerve conduction studies showed absence of voluntarily recruited motor potentials in the right flexor digitorum profundus median to right digit II. Etanercept was discontinued and following review by a paediatric neurologist, a course of IVIG was commenced. To date, however, there has been no appreciable clinical improvement. Case 2: A 7 year-old girl with oligoarticular JIA, who had commenced on etanercept 3 years prior, presented with a ten week history of selective weakness in her left hand and absent power in her flexor pollicis longus. On examination, there was an apparent weakness in her flexor pollicis longus with 0/5 power. Sensory and deep tendon reflexes were normal. Etanercept was discontinued. EMG and nerve conduction studies definitively outruled a proximal median neuropathy or any median motor problem outside of the anterior interosseous nerve. EMG did not find incontrovertible evidence of motor conduction block however this remains a possible and indeed plausible mechanism. She was referred to paediatric neurology and a course of IVIG was commenced. Conclusion While etanercept remains a widely used medication in the setting of JIA, these case studies highlight the potential neurological adverse events that can occur. To our knowledge are the first reports of persistent isolated motor neuropathy secondary to etanercept use in the paediatric population. Conflicts of Interest The authors declare no conflicts of interest.