Table 1.

Molecular Genetic Testing Used in Biotinidase Deficiency

Gene 1MethodProportion of Probands with Pathogenic Variants 2 Detectable by Method
BTD Sequence analysis 3~99% 4
Gene-targeted deletion/duplication analysis 5See footnote 6.
1.

See Table A. Genes and Databases for chromosome locus and protein.

2.

See Molecular Genetics for information on variants detected in this gene.

3.

Sequence analysis detects variants that are benign, likely benign, of uncertain significance, likely pathogenic, or pathogenic. Variants may include missense, nonsense, and splice site variants and small intragenic deletions/insertions; typically, exon or whole-gene deletions/duplications are not detected. For issues to consider in interpretation of sequence analysis results, click here.

4.

Almost all individuals with partial biotinidase deficiency have the pathogenic variant p.Asp444His in one allele of BTD in combination with a pathogenic variant for profound deficiency in the other allele [Swango et al 1998].

5.

Gene-targeted deletion/duplication analysis detects intragenic deletions or duplications. Methods used may include a range of techniques such as quantitative PCR, long-range PCR, multiplex ligation-dependent probe amplification (MLPA), and a gene-targeted microarray designed to detect single-exon deletions or duplications.

6.

Two large BTD deletions have been reported in affected individuals [Senanayake et al 2015, Wolf 2016].

From: Biotinidase Deficiency

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