We aim to investigate the genetic basis of isovaleryl-CoA dehydrogenase (IVD) gene mutations and genotype-phenotype correlations in Turkish patients. Accordingly, bi-directional sequencing was performed to screen 26 patients with isovaleric acidemia (IVA). Nine novels (c.145delC, c.234 + 3G > C, c.506_507insT, p.Glu85Gln, p.Met147Val, p.Ala268Val, p.Ile287Met, p.Gly346Asp and p.Arg382Trp) and six previously reported (c.456 + 2T > C, p.Arg21His, p.Arg21Pro, p.Arg363Cys, p.Arg363His p.Glu379Lys) pathogenic mutations were identified. Pathogenicity of the novel mutations was supported using computational programs. No clear genotype-phenotype correlation could be determined. One of the cases with the novel c.234 + 3G > C mutation has portoseptal liver fibrosis, the clinical condition that was first reported for IVA. This study is the first comprehensive report from Turkey related to IVA genetics that provides information about the high number of disease-causing novel mutations. (C) 2014 Elsevier Masson SAS. All rights reserved.