The Invitae Aniridia Test analyzes the primary gene associated with aniridia, PAX6. Aniridia is a condition that is associated with underdevelopment or absence of iris tissue. Gillespie syndrome is also caused by pathogenic variants in PAX6 and is characterized by aniridia, cerebellar ataxia, and mental retardation. In addition, pathogenic variants in PAX6 have been implicated in disorders with findings such as coloboma, cataracts, keratitis, foveal hypoplasia, optic nerve hypoplasia, and Peters anomaly.
Analysis of the PAX6 gene may help guide treatment and management decisions. Identification of a disease-causing variant would also guide testing and diagnosis of at-risk relatives.
About a third of individuals with aniridia have a contiguous gene deletion that encompasses both the PAX6 and WT1 genes and that causes Wilms tumor, aniridia, genitourinary anomalies, and mental retardation (WAGR) syndrome. In the presence of any of these additional features, the WAGR syndrome test may be more appropriate.
Aniridia is a congenital sight-threatening disorder that is caused by haploinsufficiency of the PAX6 gene and is characterized by bilateral underdevelopment or absence of iris tissue. Most individuals with aniridia have foveal hypoplasia with reduced visual acuity and nystagmus, and many develop keratopathy, cataracts, or glaucoma, leading to a progressive decline in vision. Some affected individuals can also have microcornea, ectopia pupillae, optic nerve coloboma, ptosis, hypermetropia, myopia, Peters anomaly, anophthalmia, or microphthalmia. Aniridia can occasionally be associated with non-ocular findings, including hearing abnormalities and reduced olfaction. Rare individuals with more severe congenital abnormalities and compound heterozygous mutations in PAX6 have been reported.
About a third of individuals with aniridia have a contiguous gene deletion that encompasses both the PAX6 and WT1 genes and that causes Wilms tumor, aniridia, genitourinary anomalies, and mental retardation (WAGR) syndrome. Individuals with WAGR syndrome are at an increased risk of Wilms tumor: Approximately 50%–70% of these individuals develop Wilms tumor.
Pathogenic variants in PAX6 account for 77% of isolated aniridia without family history and approximately 80% of isolated aniridia with family history.
The disorders associated with PAX6 are inherited in an autosomal dominant manner.
Aniridia is 100% penetrant, although expressivity is variable and some features may not be readily apparent without a detailed clinical assessment.
The prevalence of aniridia is approximately 1 in 40,000 to 1 in 100,000 individuals, with a lower prevalence of about 1 in 133,931 individuals noted in the Chinese population.
Invitae is a College of American Pathologists (CAP)-accredited and Clinical Laboratory Improvement Amendments (CLIA)-certified clinical diagnostic laboratory performing full-gene sequencing and deletion/duplication analysis using next-generation sequencing technology (NGS).
Our sequence analysis covers clinically important regions of each gene, including coding exons, +/- 10 base pairs of adjacent intronic sequence in the transcript listed below. In addition, analysis covers the select non-coding variants specifically defined in the table below. Any variants that fall outside these regions are not analyzed. Any specific limitations in the analysis of these genes are also listed in the table below.
Based on validation study results, this assay achieves >99% analytical sensitivity and specificity for single nucleotide variants, insertions and deletions <15bp in length, and exon-level deletions and duplications. Invitae's methods also detect insertions and deletions larger than 15bp but smaller than a full exon but sensitivity for these may be marginally reduced. Invitae’s deletion/duplication analysis determines copy number at a single exon resolution at virtually all targeted exons. However, in rare situations, single-exon copy number events may not be analyzed due to inherent sequence properties or isolated reduction in data quality. Certain types of variants, such as structural rearrangements (e.g. inversions, gene conversion events, translocations, etc.) or variants embedded in sequence with complex architecture (e.g. short tandem repeats or segmental duplications), may not be detected. Additionally, it may not be possible to fully resolve certain details about variants, such as mosaicism, phasing, or mapping ambiguity. Unless explicitly guaranteed, sequence changes in the promoter, non-coding exons, and other non-coding regions are not covered by this assay. Please consult the test definition on our website for details regarding regions or types of variants that are covered or excluded for this test. This report reflects the analysis of an extracted genomic DNA sample. In very rare cases, (circulating hematolymphoid neoplasm, bone marrow transplant, recent blood transfusion) the analyzed DNA may not represent the patient's constitutional genome.
|Gene||Transcript reference||Sequencing analysis||Deletion/Duplication analysis|