Homocystinuria
| Homocystinuria | |
|---|---|
 |
|
| Homocysteine | |
| Classification and external resources | |
| Specialty | endocrinology |
| ICD-10 | E72.1 |
| ICD-9-CM | 270.4 |
| OMIM | 236200 |
| DiseasesDB | 5991 |
| MedlinePlus | 001199 |
| eMedicine | derm/708 |
| Patient UK | Homocystinuria |
| MeSH | D006712 |
| GeneReviews | |
Classical homocystinuria, also known as cystathionine beta synthase deficiency or CBS deficiency, is an inherited disorder of the metabolism of the amino acid methionine, often involving cystathionine beta synthase. It is an inherited autosomal recessive trait, which means a child needs to inherit a copy of the defective gene from both parents to be affected.
This defect leads to a multi-systemic disorder of the connective tissue, muscles, central nervous system (CNS), and cardiovascular system. Homocystinuria represents a group of hereditary metabolic disorders characterized by an accumulation of the amino acid homocysteine in the serum and an increased excretion of homocysteine in the urine. Infants appear to be normal and early symptoms, if any are present, are vague.
Signs and symptoms of homocystinuria that may be seen include the following:
It is caused by the deficiency of the enzyme cystathionine beta synthase, and the deficiency of folic acid, vitamin B12 and pyridoxine (vitamin B6).
The term homocystinuria describes an increased excretion of the thiol amino acid homocysteine in urine (and incidentally, also an increased concentration in plasma). The source of this increase may be one of many metabolic factors, only one of which is CBS deficiency. Others include the re-methylation defects (cobalamin defects, methionine sythase deficiency, MTHFR) and vitamin deficiencies (cobalamin (vitamin B12) deficiency, folate (vitamin B9) deficiency, riboflavin deficiency (vitamin B2), pyridoxal phosphate deficiency (vitamin B6)). In light of this information, a combined approach to laboratory diagnosis is required to reach a differential diagnosis.
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