Biotin deficiency is a rare nutritional disorder caused by a deficiency of the water-soluble B vitamin termed biotin. This article discusses biotin deficiency caused by deficiency of the enzyme biotinidase (see also Biotinidase Deficiency). Over 140 different genetic defects have been noted with biotinase. [1] At least 25 countries have included biotinidase deficiency in their screening programs for neonatal disease.     Biotin deficiency rarely, if ever, occurs in healthy individuals who consume a regular diet unless they are being treated either with certain anticonvulsants or with broad-spectrum antibiotics. The extremely low prevalence of biotin deficiency is probably the result of a combination of factors. First, the daily requirement for biotin is low (approximately 150-300 µg/d). Second, almost all foods contain significant quantities of biotin, and many widely consumed foods are relatively rich in biotin. Third, the intestinal flora synthesizes significant quantities of biotin, and at least a portion of that biotin is believed to be absorbed into the bloodstream. Fourth, a significant fraction of the body's biotin is recycled; that is, a given molecule of biotin may be repeatedly used before it is eventually lost from the body in the feces or urine. A new mouse model of this disease has been noted and could help research on this disease. [2]