To report a novel de novo vitelliform macular dystrophy (VMD2) mutation in a patient with Best macular dystrophy.Best-corrected visual acuity, dilated fundus examination, and electro-oculography were performed in a patient with Best macular dystrophy and his parents. Both the patient and his parents also had blood samples drawn, and their DNA was analyzed by direct genomic sequencing.A heterozygous VMD2 gene missense mutation in exon 2 (Thr6Ala [ACA>GCA]) was identified in the proband. This mutation was not present in his clinically unaffected parents.A novel de novo mutation in the VMD2 gene was found in a patient whose phenotype and electro-oculographic findings were characteristic of Best macular dystrophy, whereas both parents were phenotypically and genetically unaffected. The findings in this family document that a de novo mutation needs to be considered when an isolated family member is found to have a Best disease phenotype.