BTD

More than 150 mutations in the BTD gene have been identified in people with biotinidase deficiency. This disorder, if untreated, can affect many parts of the body and cause delayed development. Most of the mutations that cause biotinidase deficiency change single amino acids in the biotinidase enzyme. These changes occur in critical regions of the enzyme and reduce or eliminate the enzyme's activity.

Most BTD gene mutations cause profound biotinidase deficiency. This severe form of the disorder results when the activity of biotinidase is reduced to less than 10 percent of normal. Other mutations cause a milder form of the condition called partial biotinidase deficiency. These mutations reduce biotinidase activity to between 10 percent and 30 percent of normal. Without enough of this enzyme, biotin cannot be recycled. The resulting shortage of free biotin impairs the activity of biotin-dependent carboxylases, leading to a buildup of potentially toxic compounds in the body. If the condition is not treated promptly, this buildup damages various cells and tissues, causing the signs and symptoms associated with biotinidase deficiency.

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