title: Observations regarding retinopathy in mitochondrial trifunctional protein deficiencies.
abstract: Although the retina is thought to primarily rely on glucose for fuel, inherited deficiency of one or more activities of mitochondrial trifunctional protein results in a pigmentary retinopathy leading to vision loss. Many other enzymatic deficiencies in fatty acid oxidation pathways have been described, none of which results in retinal complications. The etiology of retinopathy among patients with defects in trifunctional protein is unknown. Trifunctional protein is a heteroctomer; two genes encode the alpha and beta subunits of TFP respectively, HADHA and HADHB. A common mutation in HADHA, c.1528G>C, leads to a single amino acid substitution, p. Glu474Gln, and impairs primarily long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) activity leading to LCHAD deficiency (LCHADD). Other mutations in HADHA or HADHB often lead to significant reduction in all three enzymatic activities and result in trifunctional protein deficiency (TFPD). Despite many similarities in clinical presentation and phenotype, there is growing evidence that they can result in different chronic complications. This review will outline the clinical similarities and differences between LCHADD and TFPD, describe the course of the associated retinopathy, propose a genotype/phenotype correlation with the severity of retinopathy, and discuss the current theories about the etiology of the retinopathy.
authors.affiliation: Department of Molecular & Medical Genetics, School of Medicine, Oregon Health & Science University, Mail Code L-103, 3181 SW Sam Jackson Park Rd Portland, OR 97239, USA. fletchea@ohsu.edu
authors.forename: Autumn L
authors.initials: AL
authors.lastname: Fletcher
authors.forename: Mark E
authors.initials: ME
authors.lastname: Pennesi
authors.forename: Cary O
authors.initials: CO
authors.lastname: Harding
authors.forename: Richard G
authors.initials: RG
authors.lastname: Weleber
authors.forename: Melanie B
authors.initials: MB
authors.lastname: Gillingham
mesh_terms: D044942:Acyl-CoA Dehydrogenase, Long-Chain / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008052:Lipid Metabolism, Inborn Errors / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology / Q000473:pathology*; D063991:Mitochondrial Trifunctional Protein; D063992:Mitochondrial Trifunctional Protein, alpha Subunit; D063993:Mitochondrial Trifunctional Protein, beta Subunit; D009097:Multienzyme Complexes / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D012160:Retina / Q000201:enzymology / Q000473:pathology; D012164:Retinal Diseases / Q000235:genetics / Q000378:metabolism*
chemical_list: D009097:Multienzyme Complexes; C576205:HADHA protein, human; D063992:Mitochondrial Trifunctional Protein, alpha Subunit; D044942:Acyl-CoA Dehydrogenase, Long-Chain; C576206:HADHB protein, human; D063991:Mitochondrial Trifunctional Protein; D063993:Mitochondrial Trifunctional Protein, beta Subunit