Case report: Aqueous and Vitreous amino-acid concentrations in a patient with maple syrup urine disease operated on rhegmatogenous retinal detachment
Kanakis et al. BMC Ophthalmology
Case report: Aqueous and Vitreous amino- acid concentrations in a patient with maple syrup urine disease operated on rhegmatogenous retinal detachment
Menelaos G. Kanakis 0
Helen Michelakakis 1
Petros Petrou 0
Chrysanthi Koutsandrea 0
Ilias Georgalas 0
0 1st Department of Ophthalmology, “G. Gennimatas” Hospital of Athens, National and Kapodistrian University of Athens , Mesogeion 154, Athens 11527 , Greece
1 Department Enzymology and Cellular Function, Institute of Child Health , 7 Fokidos street, Athens 11526 , Greece
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. Case presentation: 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.
Case report; Maple syrup urine disease; Retinal detachment; Amino acid concentration; Vitreous
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Background
MSUD is a rare (1:200,000) genetic metabolic disease,
caused by a defect in branched chain ketoacid
dehydrogenase (BCKA), leading to elevated concentrations of
the branched-chain amino acids leucine, isoleucine, and
valine [1]. This enzyme is a supra enzyme complex
consisting of multiple copies of four distinct subunits and is
located in the inner wall of the mitochondrion. The
disease has autosomal-recessive inheritance. Ocular
complications of untreated disease or late diagnosis include
optic atrophy, nystagmus, ophthalmoplegia, strabismus,
and cortical blindness [2].
Case presentation
A 24 year old Caucasian female was admitted to our
hospital when diagnosed with Rhegmatogenous Retinal
Detachment (RRD), on her left eye. The patient also
suffers from maple syrup urine disease (MSUD), for which
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she has been maintained on a special diet and
thiamine supplements, autismus (under treatment
with quetiapine, oxcarbazepine and fluvoxamine), and
ulcerative colitis (under treatment with mesalamine)
(Table 1) (Additional file 1).
Dilated fundus examination revealed an inferior retinal
detachment (3 – 8th h), macula off. The detachment had
been discovered 12 days ago and there were not any signs
of Proliferative vitreoretinopathy (PVR). The patient was
operated on successfully under general anesthesia, with
23G Vitrectomy (Constellation Vitrectomy System, Alcon
Laboratories, Texas, USA), and is under follow up for the
last four months. Apart from the successfully treated
retinal detachment, slit lamp biomicroscopy and fundus
examination were unremarkable on admission and during
the follow up period.
Informed consent of the custodian (mother) was
obtained, since the patient is mentally retarded due to
MSUD. Undiluted vitrectomy samples (approx (...truncated)