Table 1.

Molecular Genetic Testing Used in Aromatic L-Amino Acid Decarboxylase Deficiency

Gene 1MethodProportion of Pathogenic Variants 2 Detectable by Method
DDC Sequence analysis 3>99% 4, 5, 6
Gene-targeted deletion/duplication analysis 7Rare 8
1.
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.

Data derived from the subscription-based professional view of Human Gene Mutation Database [Stenson et al 2020]

5.

The spectrum of variants identified in DDC and reported by Himmelreich et al [2022] include about 51% pathogenic missense variants, 15% pathogenic splice site variants, 3% pathogenic frameshift variants, 2% pathogenic nonsense variants, 1% pathogenic in-frame variants, and the remaining are classified as variants of unknown clinical significance.

6.

A pathogenic founder variant, c.714+4A>T, has been observed in individuals of Asian (particularly Chinese, Taiwanese, or Japanese) ancestry [Hwu et al 2018, Dai et al 2020, Wen et al 2020].

7.

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.

8.

One single large deletion has been reported [Himmelreich et al 2022].

From: Aromatic L-Amino Acid Decarboxylase Deficiency

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