The siblings we describe here were reported previously by us5 to have a homozygous variant in STXBP5L (c.3127G>A, p.Val1043Ile) associated with a phenotype summarised as an infantile-onset neurodegenerative disorder, manifesting a predominant sensorimotor axonal neuropathy, optic atrophy and cognitive deficit. This evidence concerns the gene STXBP5L and Cognitive impairment.