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GTR Home > Conditions/Phenotypes > Classic homocystinuria

Classic homocystinuria

Synonyms
CBS deficiency; Cystathionine beta-synthase deficiency; HOMOCYSTINURIA WITH OR WITHOUT RESPONSE TO PYRIDOXINE; Homocystinuria Caused by Cystathionine Beta-Synthase Deficiency; Homocystinuria due to CBS deficiency; Homocystinuria due to cystathionine beta-synthase deficiency
Modes of inheritance
Autosomal recessive inheritance (Orphanet)

Summary

Excerpted from the GeneReview: Homocystinuria Caused by Cystathionine Beta-Synthase Deficiency
Homocystinuria caused by cystathionine β-synthase (CBS) deficiency is characterized by involvement of the eye (ectopia lentis and/or severe myopia), skeletal system (excessive height, long limbs, scolioisis, and pectus excavatum), vascular system (thromboembolism), and CNS (developmental delay/intellectual disability). All four ‒ or only one ‒ of the systems can be involved; expressivity is variable for all of the clinical signs. It is not unusual for a previously asymptomatic individual to present in adult years with only a thromboembolic event that is often cerebrovascular. Two phenotypic variants are recognized, B6-responsive homocystinuria and B6-non-responsive homocystinuria. B6-responsive homocystinuria is usually milder than the non-responsive variant. Thromboembolism is the major cause of early death and morbidity. IQ in individuals with untreated homocystinuria ranges widely, from 10 to 138. In B6-responsive individuals the mean IQ is 79 versus 57 for those who are B6-non-responsive. Other features that may occur include: seizures, psychiatric problems, extrapyramidal signs (e.g., dystonia), hypopigmentation of the skin and hair, malar flush, livedo reticularis, and pancreatitis.
Full text of GeneReview (by section):
Summary
Diagnosis
Clinical Characteristics
Genetically Related (Allelic) Disorders
Differential Diagnosis
Management
Genetic Counseling
Resources
Molecular Genetics
References
Chapter Notes
Authors:
Stephanie J Sacharow
Jonathan D Picker
Harvey L Levy
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Available tests

118 tests are in the database for this condition.

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Clinical tests (118 available)

Biochemical Genetics Tests

Molecular Genetics Tests

Genes See tests for all associated and related genes

  • Also known as: CBSL, HIP4, CBS
    Summary: cystathionine beta-synthase

Clinical features

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Imported from Human Phenotype Ontology (HPO)

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Reviews

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
  • ACMG ACT, 2012
    American College of Medical Genetics and Genomics, Transition to Adult Health Care ACT Sheet, Homocystinuria (CBS Deficiency), 2012

Molecular resources

Consumer resources

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