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GTR Home > Conditions/Phenotypes > Homocystinuria


Homocystinuria is an inherited disorder in which the body is unable to process certain building blocks of proteins (amino acids) properly. \n\nThe most common form of homocystinuria, called classic homocystinuria, is characterized by tall stature, nearsightedness (myopia), dislocation of the lens at the front of the eye, a higher risk of blood clotting disorders, and brittle bones that are prone to fracture (osteoporosis) or other skeletal abnormalities. Some affected individuals also have developmental delay and learning problems.\n\nLess common forms of homocystinuria can cause intellectual disability, slower growth and weight gain (failure to thrive), seizures, and problems with movement. They can also cause and a blood disorder called megaloblastic anemia, which occurs when a person has a low number of red blood cells (anemia), and the remaining red blood cells are larger than normal (megaloblastic).\n\nThe signs and symptoms of homocystinuria typically develop during childhood, although some mildly affected people may not show signs and symptoms until adulthood. [from MedlinePlus Genetics]

Clinical resources

Practice guidelines

  • ACMG ACT, 2021
    American College of Medical Genetics and Genomics, Newborn Screening ACT Sheet, Elevated Methionine +/- Elevated Homocysteine, Homocystinuria (Cystathionine beta-synthase deficiency), 2021
  • ACMG Algorithm, 2021
    American College of Medical Genetics and Genomics, Algorithm, Elevated Methionine +/- Elevated Homocysteine, 2021
  • Orphanet, 2013
    Orphanet, Classic Homocystinuria, 2013

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