title: Case report: Aqueous and Vitreous amino-acid concentrations in a patient with maple syrup urine disease operated on rhegmatogenous retinal detachment.
abstract: BACKGROUND
  Maple syrup urine disease (MSUD) is a rare metabolic disorder, affecting the metabolism of branched chain amino-acids (Valine, Leukine, Isoleukine). We present a rare case of rhegmatogenous retinal detachment (RRD) in a MSUD patient.
  
  
  METHODS
  We performed amino acid analysis of aqueous humour, vitreous and serum samples obtained during surgery from a 24 year old female MSUD patient successfully operated on RRD. Serum values for a-amino-butyric acid, valine, isoleucine, leucine, tyrosine, phenylalanine, ornithine and histidine were low, while values for citrulline, methionine and lysine were borderline low, all attributed to the patient's special diet. Serum glutamate was above normal, probably due to the breakdown of glutamine to glutamate. In the aqueous and vitreous the amino acids implicated in MSUD (Valine, Leukine Isoleukine), were within normal range. Glutamate was absent in the vitreous and presented low levels in the aqueous. Glutamate has been reported to play an important role in retinal damage. Elevated glutamate levels have been reported in vitreous specimens from patients subjected to vitrectomy or buckling surgery for RRD. In MSUD, glutamate has been implicated in the pathogenesis of brain damage. Low levels of glutamate have been observed in the cerebellum of experimental MSUD animals, as well as postmortem brain tissue from a child that died of leucine intoxication. The reduction was attributed to the elevation of a-ketoisocaproic which reverses the net direction of nitrogen flow. It could be argued that this could impact on amino acid concentration in aqueous and vitreous fluids.
  
  
  CONCLUSIONS
  Although no definite conclusions can be drawn by this extremely rare case, the low vitreous and aqueous levels of Glutamate is an interesting finding. Further studies are needed to provide a better insight in the role of amino acids as neurotransmitters in the human eye in health and disease.
authors.affiliation: 1st Department of Ophthalmology, "G. Gennimatas" Hospital of Athens, National and Kapodistrian University of Athens, Mesogeion 154, Athens, 11527, Greece. mkanakis@otenet.gr.
authors.forename: Menelaos G
authors.initials: MG
authors.lastname: Kanakis
authors.affiliation: Department Enzymology and Cellular Function, Institute of Child Health, 7 Fokidos street, Athens, 11526, Greece.
authors.forename: Helen
authors.initials: H
authors.lastname: Michelakakis
authors.affiliation: 1st Department of Ophthalmology, "G. Gennimatas" Hospital of Athens, National and Kapodistrian University of Athens, Mesogeion 154, Athens, 11527, Greece.
authors.forename: Petros
authors.initials: P
authors.lastname: Petrou
authors.affiliation: 1st Department of Ophthalmology, "G. Gennimatas" Hospital of Athens, National and Kapodistrian University of Athens, Mesogeion 154, Athens, 11527, Greece.
authors.forename: Chrysanthi
authors.initials: C
authors.lastname: Koutsandrea
authors.affiliation: 1st Department of Ophthalmology, "G. Gennimatas" Hospital of Athens, National and Kapodistrian University of Athens, Mesogeion 154, Athens, 11527, Greece.
authors.forename: Ilias
authors.initials: I
authors.lastname: Georgalas
mesh_terms: D000596:Amino Acids / Q000032:analysis*; D001082:Aqueous Humor / Q000737:chemistry*; D005260:Female; D006801:Humans; D008375:Maple Syrup Urine Disease / Q000378:metabolism*; D012163:Retinal Detachment / Q000378:metabolism* / Q000601:surgery; D014822:Vitreous Body / Q000737:chemistry*; D055815:Young Adult
chemical_list: D000596:Amino Acids
keywords: Amino acid concentration; Case report; Maple syrup urine disease; Retinal detachment; Vitreous