Biotinidase deficiency
From Wikipedia, the free encyclopedia
| Biotinidase deficiency | |
| Classification and external resources | |
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|---|---|
| Biotin | |
| ICD-9 | 277.6 |
| OMIM | 253260 |
| DiseasesDB | 29822 |
| eMedicine | ped/239 |
| MeSH | D028921 |
Biotinidase deficiency is an autosomal recessive metabolic disorder in which the body is not able to process the nutrient biotin properly.
Biotin, sometimes called vitamin H, is an important water-soluble nutrient that aids in the metabolism of fats, carbohydrates and proteins. Biotin deficiency can result in behavioral disorders, lack of coordination, learning disabilities and seizure. Biotin supplementation can alleviate and sometimes totally arrest such symptoms.
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[edit] Epidemiology
Based on the results of worldwide screening of biotinidase deficiency in 1991, the incidence of the disorder is:
One in 137,401 for profound biotinidase deficiency
One in 109,921 for partial biotinidase deficiency
One in 61,067 for the combined incidence of profound and partial biotinidase deficiency
Carrier frequency in the general population is approximately one in 120.
[edit] Symptoms
Symptoms of a biotinidase deficiency can appear several days after birth. These include: seizures, hypotonia, ataxia, hearing loss, optic atrophy, skin rash and alopecia.
If left untreated, the disorder can eventually lead to coma and death.
It is recommended that raw eggs should be avoided in those affected by biotin deficiency, as eggs contain high levels of avidin. This binds to biotin making it unavailable for use elsewhere in the body.
[edit] Genetics
Mutations in the BTD gene cause biotinidase deficiency. Biotinidase is the enzyme that is made by the BTD gene. Many mutations that cause the enzyme to be nonfunctional or to be made at extremely low levels have been identified. Biotin is a vitamin that is chemically bound to proteins. (Most vitamins are only loosely associated with proteins.) Without biotinidase activity, the vitamin biotin cannot be separated from foods and therefore cannot be used by the body. Another function of the biotinidase enzyme is to recycle biotin from enzymes that are important in metabolism (processing of substances in cells). When biotin is lacking, specific enzymes called carboxylases cannot process proteins, fats, or carbohydrates. Individuals lacking biotinidase activity can still have normal carboxylases if they ingest small amounts of biotin.
This condition is inherited in an autosomal recessive pattern, which means the defective gene is located on an autosome, and two copies of the defective gene - one from each parent - must be inherited for a person to be affected by the disorder. The parents of a child with an autosomal recessive disorder are usually not affected by the disorder, but are carriers of one copy of the defective gene. If both parents are carriers for the biotinidase deficiency, there is a 25% chance that their child will be born with it and a 75% chance that they will be carriers. The chromosomal locus is at 3p25. The gene has 4 exons of lengths 79bp, 265bp, 150bp and 1502bp respectively. There are at least 21 different mutations that have been found to lead to biotinidase deficiency. The two most common mutations are a seven base deletion/ three base insertion and a mutation.
[edit] Diagnosis
Biotinidase deficiency can be found by genetic testing. This is often done at birth in several states throughout the United States. Results are found through testing a small amount of blood gathered through a heel prick of the infant. Not all states require that this test be done so it is often skipped in those where it is not required. It can also be found by sequencing the BTD gene.
[edit] Pathophysiology
Symptoms of the disease are caused by the inability to reuse biotins that are needed for cell growth, production of fatty acids and the metabolism of fats and amino acids. For the most part, there is no real progression. If left untreated, the symptoms can lead to later problems such as comas or death. The problems that are prevalent early in life remain prevalent in old age unless treatment is administered daily.
[edit] Treatment
Treatment is possible but unless continued daily, problems may arise. Currently, this is done through the taking of 5-10 mg of oral biotin a day. If symptoms have begun to show, standard treatments can take care of them, such as corrective lenses for mild cases of optic atrophy and hearing aids for poor hearing.
[edit] See also
[edit] External links
This article incorporates public domain material from the United States National Library of Medicine document "Genetics Home Reference".
[edit] References
- Dobrowolski SF, Angeletti J, Banas RA, Naylor EW (2003). "Real time PCR assays to detect common mutations in the biotinidase gene and application of mutational analysis to newborn screening for biotinidase deficiency". Mol Genet Metab 78 (2): 100–7. doi:. PMID 12618081
- McMahon RJ (2002). "Biotin in metabolism and molecular biology". Annu Rev Nutr 22: 221–39. doi:. PMID 12055344
- Neto EC, Schulte J, Rubim R, Lewis E, DeMari J, Castilhos C, Brites A, Giugliani R, Jensen KP, Wolf B (2004). "Newborn screening for biotinidase deficiency in Brazil: biochemical and molecular characterizations". Braz J Med Biol Res 37 (3): 295–9. doi:. PMID 15060693
- Weber P, Scholl S, Baumgartner ER (2004). "Outcome in patients with profound biotinidase deficiency: relevance of newborn screening". Dev Med Child Neurol 46 (7): 481–4. doi:. PMID 15230462
- Wolf B (2003). "Biotinidase Deficiency: New Directions and Practical Concerns". Curr Treat Options Neurol 5 (4): 321–328. doi:. PMID 12791199
- Wolf, Barry (2008), "Biotinidase Deficiency -- GeneReviews -- NCBI Bookshelf" (w), Tropical Medicine & International Health 4: 284, doi:, http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene∂=biotin
- Kniffin, Cassandra L. (2004), "OMIM - Biotinidase Deficiency", Tropical Medicine & International Health 4: 284, doi:, http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=253260
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