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{{Infobox medical condition (new) |
{{Infobox medical condition (new) |
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| name = Biotinidase deficiency |
| name = Biotinidase deficiency |
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| image = Biocytin.svg |
| image = Biocytin.svg |
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| caption = [[Biocytin]], one of the ''in vivo'' subtrates of [[biotinidase]] |
| caption = [[Biocytin]], one of the ''in vivo'' subtrates of [[biotinidase]]. |
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| synonyms = BTD |
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'''Biotinidase deficiency''' is an [[autosomal recessive]] [[metabolic disorder]] in which [[biotin]] is not released from proteins in the diet during digestion or from normal protein turnover in the cell. This situation results in [[biotin deficiency]]. |
'''Biotinidase deficiency''' is an [[autosomal recessive]] [[metabolic disorder]] in which [[biotin]] is not released from proteins in the diet during digestion or from normal protein turnover in the cell. This situation results in [[biotin deficiency]]. |
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Biotin is an important water-soluble nutrient that aids in the [[metabolism]] of [[fat]]s, [[carbohydrate]]s, and [[protein]]s. Biotin deficiency can result in behavioral disorders, lack of coordination, learning disabilities and [[seizure]]s. Biotin supplementation can alleviate and sometimes totally stop such symptoms. |
[[Biotin]] is an important water-soluble nutrient that aids in the [[metabolism]] of [[fat]]s, [[carbohydrate]]s, and [[protein]]s. Biotin deficiency can result in behavioral disorders, lack of coordination, learning disabilities and [[seizure]]s. Biotin supplementation can alleviate and sometimes totally stop such symptoms. |
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==Signs and symptoms== |
==Signs and symptoms== |
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Signs and symptoms of a biotinidase deficiency |
Signs and symptoms of a biotinidase deficiency can appear several days after birth. These include [[seizure]]s, [[hypotonia]] and muscle/limb weakness, [[ataxia]], [[paresis]], [[hearing loss]], [[optic atrophy]], skin rashes (including [[seborrheic dermatitis]] and [[psoriasis]]), and [[alopecia]]. If left untreated, the disorder can rapidly lead to [[coma]] and death.{{citation needed|date=September 2020}} |
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Neonates with BTD may not exhibit any signs, and symptoms typically appear after the first few weeks or months of life. If left untreated, around 70% of infants with BTD will experience seizures (staring spells, jerking limb movements, stiffness, flickering eyelids), which often acts as the first symptom of BTD. Infants with BTD may also have weak muscles and hypotonia; this may cause infants to appear abnormally "floppy" and have affected feeding and motor skills. BTD may result in developmental delays, vision or hearing problems, eye infections, alopecia, and eczema. The urine of infants with BTD may contain lactic acid and ammonia. Other symptoms that infants may exhibit include ataxia, breathing issues, lethargy, hepatomegaly, splenomegaly, and speech problems. The condition may eventually result in a coma and death.<ref>{{cite web |title=Biotinidase Deficiency |url=https://rarediseases.org/rare-diseases/biotinidase-deficiency/ |website=NORD |access-date=18 February 2023}}</ref> |
Neonates with BTD may not exhibit any signs, and symptoms typically appear after the first few weeks or months of life. If left untreated, around 70% of infants with BTD will experience seizures (staring spells, jerking limb movements, stiffness, flickering eyelids), which often acts as the first symptom of BTD. Infants with BTD may also have weak muscles and hypotonia; this may cause infants to appear abnormally "floppy" and have affected feeding and motor skills. BTD may result in developmental delays, vision or hearing problems, eye infections, alopecia, and eczema. The urine of infants with BTD may contain lactic acid and ammonia. Other symptoms that infants may exhibit include ataxia, breathing issues, lethargy, hepatomegaly, splenomegaly, and speech problems. The condition may eventually result in a coma and death.<ref>{{cite web |title=Biotinidase Deficiency |url=https://rarediseases.org/rare-diseases/biotinidase-deficiency/ |website=NORD |access-date=18 February 2023}}</ref> |
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Biotinidase deficiency can also appear later in life. This is referred to as "late-onset" biotinidase deficiency. The symptoms are similar, but perhaps more mild, because if an individual survives the neonatal period they likely have some residual activity of biotin-related enzymes. Studies<ref name=pmid9375914>{{cite journal |last1=Wolf |first1=Barry |last2=Norrgard |first2=Karen |last3=Pomponio |first3=Robert J. |last4=Mock |first4=Donald M. |last5=Secor Mcvoy |first5=Julie R. |last6=Fleischhauer |first6=Kristin |last7=Shapiro |first7=Steven |last8=Blitzer |first8=Miriam G. |last9=Hymes |first9=Jeanne |title=Profound biotinidase deficiency in two asymptomatic adults |journal=American Journal of Medical Genetics |volume=73 |issue=1 |pages=5–9 |year=1997 |pmid=9375914 |doi=10.1002/(SICI)1096-8628(19971128)73:1<5::AID-AJMG2>3.0.CO;2-U }}</ref><ref name=pmid2295967>{{cite journal |first1=Julie R. Secor |last1=McVoy |first2=Harvey L. |last2=Levy |first3=Michael |last3=Lawler |first4=Michael A. |last4=Schmidt |first5=Douglas D. |last5=Ebers |first6=Suzanne |last6=Hart |first7=Denise Dove |last7=Pettit |first8=Miriam G. |last8=Blitzer |first9=Barry |last9=Wolf |title=Partial biotinidase deficiency: Clinical and biochemical features |journal=The Journal of Pediatrics |volume=116 |issue=1 |pages=78–83 |year=1990 |pmid=2295967 |doi=10.1016/S0022-3476(05)81649-X }}</ref> have noted individuals who were asymptomatic until adolescence or early adulthood. One study pointed out that untreated individuals may not show symptoms until age 21.<ref>{{cite journal |last1=Möslinger |first1=Dorothea |last2=Mühl |first2=Adolf |last3=Suormala |first3=Terttu |last4=Baumgartner |first4=Regula |last5=Stöckler-Ipsiroglu |first5=Sylvia |title=Molecular characterisation and neuropsychological outcome of 21 patients with profound biotinidase deficiency detected by newborn screening and family studies |journal=European Journal of Pediatrics |volume=162 |pages=S46–9 |year=2003 |pmid=14628140 |doi=10.1007/s00431-003-1351-3|s2cid=6490712 }}</ref> Furthermore, in rare cases, even individuals with profound deficiencies of biotinidase can be asymptomatic.<ref name=pmid9375914/> |
Biotinidase deficiency can also appear later in life. This is referred to as "late-onset" biotinidase deficiency. The symptoms are similar, but perhaps more mild, because if an individual survives the neonatal period they likely have some residual activity of biotin-related enzymes. Studies<ref name=pmid9375914>{{cite journal |last1=Wolf |first1=Barry |last2=Norrgard |first2=Karen |last3=Pomponio |first3=Robert J. |last4=Mock |first4=Donald M. |last5=Secor Mcvoy |first5=Julie R. |last6=Fleischhauer |first6=Kristin |last7=Shapiro |first7=Steven |last8=Blitzer |first8=Miriam G. |last9=Hymes |first9=Jeanne |title=Profound biotinidase deficiency in two asymptomatic adults |journal=American Journal of Medical Genetics |volume=73 |issue=1 |pages=5–9 |year=1997 |pmid=9375914 |doi=10.1002/(SICI)1096-8628(19971128)73:1<5::AID-AJMG2>3.0.CO;2-U }}</ref><ref name=pmid2295967>{{cite journal |first1=Julie R. Secor |last1=McVoy |first2=Harvey L. |last2=Levy |first3=Michael |last3=Lawler |first4=Michael A. |last4=Schmidt |first5=Douglas D. |last5=Ebers |first6=Suzanne |last6=Hart |first7=Denise Dove |last7=Pettit |first8=Miriam G. |last8=Blitzer |first9=Barry |last9=Wolf |title=Partial biotinidase deficiency: Clinical and biochemical features |journal=The Journal of Pediatrics |volume=116 |issue=1 |pages=78–83 |year=1990 |pmid=2295967 |doi=10.1016/S0022-3476(05)81649-X }}</ref> have noted individuals who were asymptomatic until adolescence or early adulthood. One study pointed out that untreated individuals may not show symptoms until age 21.<ref>{{cite journal |last1=Möslinger |first1=Dorothea |last2=Mühl |first2=Adolf |last3=Suormala |first3=Terttu |last4=Baumgartner |first4=Regula |last5=Stöckler-Ipsiroglu |first5=Sylvia |title=Molecular characterisation and neuropsychological outcome of 21 patients with profound biotinidase deficiency detected by newborn screening and family studies |journal=European Journal of Pediatrics |volume=162 |pages=S46–9 |year=2003 |pmid=14628140 |doi=10.1007/s00431-003-1351-3|s2cid=6490712 }}</ref> Furthermore, in rare cases, even individuals with profound deficiencies of biotinidase can be asymptomatic.<ref name=pmid9375914/> |
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Symptom severity is predictably correlated with the severity of the enzyme defect. Profound biotinidase deficiency refers to situations where enzyme activity is 10% or less.<ref name=pmid2295967/> Individuals with partial biotinidase deficiency may have enzyme activity of |
Symptom severity is predictably correlated with the severity of the enzyme defect. Profound biotinidase deficiency refers to situations where enzyme activity is 10% or less.<ref name=pmid2295967/> Individuals with partial biotinidase deficiency may have enzyme activity of 10-30%.<ref name=pmid2295967/> |
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Functionally, there is no significant difference between dietary biotin deficiency and genetic loss of biotin-related enzyme activity. In both cases, supplementation with [[biotin]] can often restore normal metabolic function and proper catabolism of [[leucine]] and [[isoleucine]].{{citation needed|date=September 2020}} |
Functionally, there is no significant difference between dietary biotin deficiency and genetic loss of biotin-related enzyme activity. In both cases, supplementation with [[biotin]] can often restore normal metabolic function and proper catabolism of [[leucine]] and [[isoleucine]].{{citation needed|date=September 2020}} |
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Biotinidase deficiency 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, a 50% chance the child will be a carrier, and a 25% chance the child will be unaffected.{{citation needed|date=September 2020}} |
Biotinidase deficiency 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, a 50% chance the child will be a carrier, and a 25% chance the child will be unaffected.{{citation needed|date=September 2020}} |
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The chromosomal locus is at 3p25. The ''BTD'' gene has |
The chromosomal locus is at 3p25. The ''BTD'' gene has 4 exons of lengths 79 bp, 265 bp, 150 bp and 1502 bp, respectively. There are at least 21 different mutations that have been found to lead to biotinidase deficiency. The most common mutations in severe biotinidase deficiency (<10% normal enzyme activity) are: p. Cys33PhefsX36, p.Gln456His, p.Arg538Cys, p.Asp444His, and p.[Ala171Thr;Asp444His]. Almost all individuals with partial biotinidase deficiency (10-30% enzyme activity) have the mutation p.Asp444His in one [[allele]] of the ''BTD'' gene in combination with a second allele.<ref>{{cite report|title=Biotinidase Deficiency|url=https://www.ncbi.nlm.nih.gov/books/NBK1322/ | access-date=May 19, 2011}}</ref> |
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==Pathophysiology== |
==Pathophysiology== |
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== External links == |
== External links == |
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* [https:// |
* [https://www.ncbi.nlm.nih.gov/omim/253260,253260,609019,253260,609019 OMIM entries on Biotinidasa deficiency] |
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{{Medical resources |
{{Medical resources |
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