First microdeletion involving only the biotinidase gene that can cause biotinidase deficiency: A lesson for clinical practice.

We report the first microdeletion (26 kb) of the biotinidase gene (BTD) that involves three of the four exons of the gene. This deletion further exemplifies the importance of performing microarray analysis or other methodologies for a deletion of the BTD gene when the enzymatic activity indicates lower activity than can be attributed to the mutations identified by DNA sequencing.