Biotinidase deficiency is a multiple carboxylase deficiency where the body is unable to use biotin. Biotin is a vitamin and a coenzyme for four carboxylases necessary for normal metabolism in humans, and it plays an important role in the metabolism of fats and amino acids, aerobic respiration, and cell growth. Children with a deficiency of the biotinidase enzyme may present with symptoms of hypotonia, developmental delays and breathing difficulties, as early as in the first few months of life. Profound deficiency may even manifest in the form of seizures. Those with a profound deficiency have less than 10% of normal biotinidase activity left. Partial biotinidase deficiency is characterized by 10-30% of enzyme activity. If not treated, this condition can lead to several complications, including hearing and vision loss, ataxia, and alopecia.