Table 1.

Molecular Genetic Testing Used in Niemann-Pick Disease Type C

Gene 1Proportion of NPC
Attributed to Pathogenic
Variants in Gene		Proportion of Pathogenic Variants 2, 3 Detectable by Method
Sequence analysis 4Gene-targeted deletion/duplication analysis 5Chromosomal microarray analysis6
NPC1 95%76%22%2%
NPC2 5%88%12%0
1.
2.

See Molecular Genetics for information on variants detected in these genes.

3.

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

4.

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.

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.

Chromosomal microarray analysis (CMA) uses oligonucleotide or SNP arrays to detect genome-wide large deletions/duplications (including NPC1 and NPC2) that cannot be detected by other methods of deletion/duplication analysis. The ability to determine the size of the deletion/duplication depends on the type of microarray used and the density of probes in the 18q11​.2 region that includes NPC1, and in the 14q24​.3 region that includes NPC2. CMA designs in current clinical use target these regions.

From: Niemann-Pick Disease Type C

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