OPA1 and hereditary optic atrophy: This syndromic optic atrophy was linked initially to autosomal recessive OPA3 pathogenic variants with elevated urinary levels of 3-methylglutaconic acid and 3-methylglutaric acid [9]—a subtype that was also known as Costeff syndrome [10,11] but recently a biallelic OPA1 inheritance has been suggested to cause Behr phenotype.