Holocarboxylase synthetase deficiency is an inherited metabolic disorder in which the body cannot use the vitamin biotin effectively. This disorder is classified as a multiple carboxylase deficiency, characterized by impaired activity of certain enzymes that depend on biotin. Symptoms are very similar to biotinidase deficiency, and treatment – large doses of biotin – is also the same.
Genetics
thumb|right|Holocarboxylase synthetase deficiency has an autosomal recessive pattern of inheritance.
Mutations in the HLCS gene cause holocarboxylase synthetase deficiency. The HLCS gene makes a holocarboxylase synthetase enzyme that attaches biotin to other molecules. Biotin, a B vitamin, is found in foods such as liver, egg yolks, and milk. It is essential for the normal production and breakdown of proteins, fats, and carbohydrates in the body. Mutations in the HLCS gene reduce the activity of holocarboxylase synthetase, preventing cells from using biotin effectively and disrupting many cellular functions.