View source for Vitamin B7 deficiency

==Background==
* Almost all food contain significant quantities of biotin, but it is most found in plants, liver, egg yolk, soybean products, and yeast.
* Daily biotin requirement is low (150-300 ug/d).
* Intestinal flora synthesizes significant quantities of biotin.
* Biotin is recycled in the body and eventually lost in urine and feces.

===Cofactor in four major carboxylation reactions===
# Acetyl-CoA Carboxylase (ACC) - Acetyl-CoA to Malonyl-CoA in Fatty Acid Synthesis
# Pyruvate Carboxylase (PC) - Pyruvate to Oxaloacetate in Gluconeogenesis
# Propinoyl-CoA Carboxylase (PCC) - Propinoyl-CoA to Methylmalonyl-CoA in Odd Chain Fatty Acid Metabolism
# Methylcrotonyl CoA Carboxylase (MCC) - 3-Methylcrotonyl CoA to 3-Methylglutaconyl CoA in Leucine Metabolism

===Biotin deficiency risk factors===
# Long-term Parenteral Nutrition
# Consumption of raw egg whites (bodybuilders or boxers)

===Secondary biotin deficiency (Multiple Carboxylase Deficiency)===
Is caused by two inherited defects in metabolism:
# Holocarboxylase Synthetase Deficiency -  Autosomal Recessive disorder. Holocarboxylase Synthetase is required to attach biotin to other molecules. Deficiency in this enzyme prevents cells from using Biotin.
# Biotinidase Deficiency - Biotinidase is required to release Biotin that is bounded to protein.

==Clinical Features==
===Classical Presentation===
* [[rash|Dermatitis]] - specifically around eyes, nose, mouth
* [[Alopecia]]
* Enteritis ([[diarrhea]], [[nausea/vomiting]])
* Neurological - including [[AMS]], [[lethargy]], [[hallucinations]], [[paresthesias]]

===Holocarboxylase Synthetase Deficiency===
Presents in the first week of life with:
* [[altered mental status (peds)|Lethargy]]
* Hypotonia
* [[Vomiting]]

===Biotinidase Deficiency===
Presents later in life with:
* [[rash|Dermatitis]]
* Neurological symptoms - [[ataxia]], [[seizures]], myoclonus, [[nystagmus]]
* [[Ketonemia|Ketoacidosis]]

==Differential Diagnosis==
* DDx involves genetic disorders with impaired carboxylation.
** Biotinidase Deficiency (see above)
** Holocarboxylase Synthetase Deficiency (see above)
** Carnitine Deficiency
** Methylmalonic Acidemia
** Propionic Acidemia
** Pyruvate Carboxylase Deficiency
* Starvation
* Medication Use - [[Antibiotics]] or [[anticonvulsants]]
* Other vitamin deficiencies:

===[[Vitamin deficiencies]]===
*[[Vitamin A deficiency]]
*Vitamin B deficiencies
**[[Vitamin B1 deficiency]] (Thiamine)
***[[Beriberi]]
***[[Wernicke-Korsakoff syndrome]]
**[[Vitamin B3 deficiency]] ([[Pellagra]])
**[[Vitamin B7 deficiency]] (Biotin)
**[[Vitamin B9 deficiency]] (Folate)
**[[Vitamin B12 deficiency]]
*Vitamin C deficiency ([[Scurvy]])
*Vitamin D deficiency ([[Rickets]])
*[[Vitamin E deficiency]]
*[[Vitamin K deficiency]]

==Evaluation==
* Diagnosis is primarily clinical. Routine serum chemistry panel should be checked.
* Other Laboratory Studies
** Newborn Screening
** Serum Biotinidase Activity decreased
** Serum Ammonia Levels increased
** Plasma Carnitine
** Quantitative Amino Acid levels
** Urine B-Hydroxyisoverlate decreased
** Urine Biotin decreased
** Urine Ketones increased

==Management==
* Supplementation of [[Biotin]]. Dosage is debated:
** 150 ug intramuscular injection suggested
** 5-20 mg/dl have also been used

* Stop consumption of raw eggs.
* Stop culprit anti-convulsant or anti-biotic

==Disposition==
* Follow-up with primary care provider or referral to genetic specialist.

==See Also==
*[[Vitamin deficiencies]]
*[[Inborn errors of metabolism]]

==External Links==


==References==
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[[Category:FEN]]