P.367 - A case of childhood onset of treatable sensory neuronopathy caused by mutations in riboflavin transporter RFVT2 presenting as pure sensory ataxia with excellent response to riboflavin – a five year follow up

Abstract

Childhood onset neuronopathies are a clinically heterogeneous group of disorders. Its original description is known as Brown-Vialetto-Van Laere syndrome and characterized by motor neuronopathy with early onset of bulbar palsy, hearing loss and respiratory failure. Sensorimotor neuronopathy was described later. No treatment was available for this neurodegenerative disorder until recent discovery of riboflavin transporters RFVT3 and RFVT2. We report a case of early childhood onset of RFVT2 related disorder due to compound heterozygous mutation p.S52F and p.L339P in the SLC52A2 gene presenting as a pure sensory ataxia associated with sensorineural hearing loss, respiratory dysfunction, optic atrophy and retinitis pigmentosa. The patient is a 2-year-old girl at the onset of her condition. Initial presentation consisted of isolated sensory ataxia. Lack of clinically evident muscle weakness and electrodiagnostic studies ruled out motor neuronopathy. 3T high resolution MRI of the brain showed abnormal T2 signal in the reticulospinal tracts. There was biochemical evidence for abnormal acylcarnitine profile. A year later patient developed hearing loss, optic nerve atrophy and retinitis pigmentosa. Polysomnogram revealed central apnea with reduced O2 concentration. We followed prospectively clinical, neurophysiological and biochemical parameters starting at baseline and after initiation of therapy with high doses of riboflavin. We report overt response to high-dose of oral riboflavin therapy in our patient. The clinical and biochemical responses in our patient consistent with reports in the literature that riboflavin supplementation can ameliorate the progression of this neurodegenerative condition, particularly when initiated early in the course and can be lifesaving. In addition, this case further broadened knowledge of this rare disorder including never reported before findings of abnormal MRI, retinitis pigmentosa and detailed characterization of respiratory dysfunction.