082 A rare mimic of inflammatory myopathy

A 37 year-old female presented with 5-weeks of neck pain, proximal weakness and dysphonia. Exami- nation showed facial rash, proximal weakness, areflexia and distal sensory loss. She had a 6-year history of sensory neuropathy, treated functional B12 deficiency and fibromyalgia. Serum showed elevated CK (360U/L) and borderline positive Anti-Ro52. Electrophysiology showed worsening sensory neuropathy and new myopathic features. She deteriorated soon after receiving intravenous corticosteroids and immu- noglobulins. CK increased to 1796 U/L and she developed bulbar failure requiring respiratory support.Muscle biopsy electron microscopy showed lipid accumulation suggesting a metabolic disorder. Serum acylcarnitines and urinary organic acids were abnormal, consistent with Riboflavin Transporter Deficiency (RTD). Riboflavin 500mg three times daily was initiated, urinary organic acids normalised and the patient regained full-power with neurorehabilitation.RTD is a rare cause of peripheral and cranial neuropathy, with autosomal recessive inheritance due to variants in riboflavin transporter genes and onset up to young adulthood. Mutation carrier frequencies should generate 70 new cases per year worldwide, though only ~80 case-reports exist in the literature suggesting under-recognition. Riboflavin is a precursor for coenzymes important for carbohydrate, amino acid and lipid metabolism. Untreated, the disorder is fatal, though the majority of patients improve with Riboflavin supplementation.elena.purcaru@gmail.com