<unk>  has an autosomal recessive pattern of inheritance. Mutations in the BTD gene cause<unk> .<unk>  is the enzyme that is made by the BTD gene. Many mutations that cause the enzyme to be nonfunctional or to be produced 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<unk>  activity, the vitamin biotin cannot be separated from foods and therefore cannot be used by the body. Another function of the<unk>  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 certain proteins, fats, or carbohydrates. Specifically, two essential branched-chain amino acids (leucine and isoleucine) are metabolized differently. Individuals lacking functional<unk>  enzymes can still have normal carboxylase activity if they ingest adequate amounts of biotin. The standard treatment regimen calls for 5–10 mg of biotin per day.<unk>  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<unk> , 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. 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<unk> . The most common mutations in severe<unk>  (<10% normal enzyme activity) are: p.Cys33PhefsX36, p.Gln456His, p.Arg538Cys, p.Asp444His, and p.Ala171Thr;Asp444His. Almost all individuals with partial<unk>  (10-30% enzyme activity) have the mutation p.Asp444His in one allele of the BTD gene in combination with a second allele.
Biotinidase deficiency
D-bifunctional protein deficiency
Glutaminase deficiency
Aromatic L-amino acid decarboxylase deficiency
Ornithine aminotransferase deficiency
Enolase deficiency
Arginine:glycine amidinotransferase deficiency
Holocarboxylase synthetase deficiency