||Biotin is a water-soluble vitamin essential for carboxylation reactions in all organisms. Biotinidase enzyme recycles biotin from biocytin and from dietary protein-bound sources. Biotinidase deficiency is inherited as an autosomal recessive trait and it presents as either profound or partial enzyme deficiency. Patients with profound enzyme deficiency have less than 10% enzyme activity; whereas partial deficiency presents as 10-30% enzyme activity.
Untreated patients with profound biotinidase deficiency exhibit neurological and cutaneous features, including seizures, hypotonia, skin rash or alopecia, developmental delay, conjunctivitis, visual problems, such as optic atrophy, and hearing loss. Metabolic disturbances include ketolactic acidosis and organic acidemia.
The sequencing assay covers 141 bases of 5' untranslated region, exons 1 to 4 and at least 20 bases into the 5' and 3' ends of all introns. Analysis for known and novel mutations in these areas of the gene is performed by bidirectional sequencing.