title: [Hyperhomocysteinemia as a risk factor for central retinal vein thrombosis in a young patient].
abstract: BACKGROUND
  Central retinal vein thrombosis (CRVT) is a multifactorial disease and known risk factors include high blood pressure, diabetes mellitus, hypercholesterolemia and primary open-angle glaucoma. Yet in patients below the age of 60, a state of hyperviscosity and hypercoagulability in the absence of other vascular risk factors are important factors, as is hyperhomocysteinemia, an independent risk factor for venous thromboses. Homocysteine is an essential amino acid produced by the transmethylation of methionine. It can be remethylated using enzymes that require folate and cobalamin to re-form methionine or to catabolize for cystathionine beta-synthetase, which is dependent on pyridoxine to form cysteine. Hyperhomocysteinemia can give rise to a dysfunction in the endothelium of the vessel, with a proliferation of vascular smooth muscle and prothrombotic homostatic changes.
  
  
  METHODS
  A male, aged 33, with no vascular risk factors except cigarette smoking who presented a sharp drop in visual acuity in the right eye. An ophthalmological examination revealed the presence of CRVT, which was confirmed by fluorescein angiography. The results of all analytical and imaging studies conducted while the patient was in hospital were negative. Later analytical monitoring showed a moderate increase in homocysteine.
  
  
  CONCLUSIONS
  From a survey of the literature we have found an important relation between CRVT and hyperhomocysteinemia, which has been noted as a potential risk factor and which requires therapy.
authors.affiliation: Servicio de Oftalmología, Hospital Virgen de la Salud, Toledo, España. mercabezas@terra.es
authors.forename: M M
authors.initials: MM
authors.lastname: Cabezas-León
authors.forename: M R
authors.initials: MR
authors.lastname: García-Montero
authors.forename: P
authors.initials: P
authors.lastname: Morente-Matas
mesh_terms: D000328:Adult; D006801:Humans; D020138:Hyperhomocysteinemia / Q000150:complications*; D008297:Male; D008875:Middle Aged; D012160:Retina / Q000473:pathology; D012170:Retinal Vein Occlusion / Q000209:etiology* / Q000473:pathology; D012307:Risk Factors; D014652:Vascular Diseases / Q000209:etiology* / Q000473:pathology