His prior genetic and metabolic workup was negative, including karyotype, array-based comparative genomic hybridization, Angelman syndrome testing, congenital disorders of glycosylation testing, HEXA gene analysis, PLP1 gene sequencing, SLC9A6 gene sequencing, peroxisomal studies, pipecolic acid, purines, pyrimidines, CSF amino acids, and basic metabolic studies. The gene discussed is PLP1; the disease is Angelman syndrome.