ACOX1 gain-of-function variation in a 10-years-old patient responsive to immunomodulating therapy.

A heterozygous gain-of-function variant in the acyl-CoA oxidase 1 (ACOX1) gene, c.710A>G (p.Asn237Ser), is known to cause Mitchell syndrome, a very rare progressive disorder characterized by episodic demyelination, sensory polyneuropathy, and hearing loss. Only eight patients have been described so far. A single patient has been treated with intravenous immunoglobulin administration, indicating clinical improvement. In this study, we describe a 10-year-old girl carrying the identical mutation, who presented with progressive sensorineural deafness, visual abnormalities, skin ichthyosis, and gait ataxia from infantile age with progressive worsening and loss of walking ability by the age of 10 years. Antioxidant therapies and monthly intravenous immunoglobulin infusions showed excellent clinical results: after 1 year of treatment, the child is now able to walk, run, and jump. We emphasize the importance of early genetic diagnosis since an effective treatment is available for this rare condition.