title: Environmental influences on familial discordance of phenotype in people with homocystinuria: a case report.
abstract: BACKGROUND
  Non-heritable factors may have an influence on the clinical expression of monogenic inherited metabolic diseases.
  
  
  METHODS
  This is a case report of a man whose mother had been diagnosed late in childhood with pyridoxine responsive homocystinuria with lens dislocation and neurodevelopmental delay. These severe complications were not observed in her son who was pyridoxine unresponsive but who had been treated appropriately since early infancy.
  
  
  CONCLUSIONS
  The phenotype of people with homocystinuria can be discordant within a family, with variability in metabolic and clinical expression depending upon both the genotype and therapeutic interventions. Offspring of people with homocystinuria should be screened in early infancy and, if positive, treated appropriately whether they have pyridoxine responsive or unresponsive disease.
authors.affiliation: Charles Dent Metabolic Unit, The National Hospital for Neurology and Neurosurgery, Queen Square, London, UK. maillot@med.univ-tours.fr
authors.forename: Francois
authors.initials: F
authors.lastname: Maillot
authors.forename: Jan P
authors.initials: JP
authors.lastname: Kraus
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Lee