Author: Dr Scott Barker MBChB, Dept of Dermatology Waikato Hospital, Hamilton, New Zealand, 2004.
Biotin is an essential micronutrient. It is one of the B vitamins and is also known as Vitamin H – ‘H’ stands for ‘haut’, the German word for skin. It is also marketed as vitamin B7 and coenzyme R
Biotin is found in many foods, and is made by bacteria, fungi, algae and certain plant species. There are particularly high amounts of biotin in brewer's yeast and in Royal Jelly. Foods containing the vitamin include liver, egg yolks, fish, meat, seeds, nuts, and vegetables.
Human tissues do not make biotin, although it is made by the bacteria that live in the large intestine.
Biotin acts as a cofactor for the function of carboxylase synthetase enzymes. Carboxylases are enzymes that catalyze the addition of a molecule of carbon dioxide to another compound to form a carboxyl group, necessary in the manufacture of fatty acids. Biotin is also involved in making glucose, some amino acids and in energy production.
These are either acquired or inherited problems that resolve when extra biotin is taken.
Biotin deficiency can be acquired by:
There are two rare inherited biotin responsive dermatoses.
Both have autosomal-recessive inheritance. This means two abnormal genes are required to cause disease, one coming from each parent. One-in-four of the parents' male and/or female children will be affected by the disease, but it is unlikely in other family members.
Holocarboxylase synthetase catalyzes bonding of biotin to the carboxylases. Deficiency of holocarboxylase synthetase results in a greater requirement for biotin and multiple carboxylase deficiency. This results in an accumulation of organic acids in the urine.
Biotinidase is required to salvage biotin for reuse during cellular turnover. It is also needed to release bound ingested biotin for absorption. A shortage of the enzyme results in a greater requirement for the vitamin than normal.
The inherited conditions causing biotin deficiency usually present in the first few weeks of life. The major features of biotin responsive dermatoses are rash and neurological problems. The rash is red and scaly and sometimes there are erosions. It develops over most of the body and may resemble psoriasis, seborrhoeic dermatitis or ichthyosis. It is especially prominent around the eyes, nose, mouth, ears and genitals. Alopecia (hair loss) and conjunctivitis (red eyes) may be present.
Progressive severe neurological symptoms develop in the untreated inherited conditions. These include seizures, developmental delay, poor feeding and death.
For adults with acquired Biotin deficiency the rash is similar but neurological symptoms include hyperaesthesia (sensitive skin), paraesthesia (pins and needles), depression and muscle pain.
Holocarboxylase synthetase deficiency and biotinidase deficiency are diagnosed in the neonatal and infant period respectively by finding high levels of organic acids in urine. Blood tests can then be done on white cells and plasma to measure enzyme levels to confirm the diagnosis.
Acquired biotin deficiency is diagnosed on clinical grounds and response to treatment.
A trial of biotin should be given in those with suspected or confirmed biotin deficiency. Usually a dose of 10–20 mg per day will be adequate. Biotinidase deficiency usually responds rapidly and dramatically to as little as 10 mg per day.
Holocarboxylase synthetase deficiency may require much larger doses. There are reports of poor response even to 200 mg/day.
There are unconfirmed reports that biotin supplements may also be helpful for a rare congenital hair disorder called the ‘uncombable hair syndrome', also known as ‘spun-glass hair’ and ‘cheveux incoiffables’. Although it has been added to many cosmetic hair products, it is uncertain whether it is of any benefit for those with normal hair.
Biotin 300 micrograms daily may also be useful for thin, brittle fingernails and those with lamellar splitting, but this is unconfirmed.
Biotin may be useful in at least some cases of Leiner disease.
The daily recommended intake for a healthy adult is 30 micrograms (µg), but many multivitamin and biotin supplements contain much higher doses, ranging from 5,000 µg (5 mg) to 10,000 µg (10 mg). Supplements can interfere with the results of common immunoassay blood tests that use biotin technology, particularly thyroid function tests. Inaccurate test results could result in overtreatment, undertreatment and even death of the patient.
If test results are not those expected clinically, the biotin-containing supplement should be discontinued for 3 days before repeating the tests.
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