Leber congenital amaurosis (LCA) is characterized by poor vision beginning between birth or early childhood, nystagmus, an initially normal fundus exam and a nonrecordable electroretinogram (ERG). In addition, other typical findings include defective pupillary responses, photophobia, and the characteristic Franceschetti\'s oculo-digital sign. Over time, macular coloboma and pigmentary retinopathy may develop. Due to the early manifestation of LCA, other syndromic or nonsyndromic conditions may be incorrectly diagnosed as LCA. LCA is most commonly inherited in an autosomal recessive manner. Please note, the NMNAT1 gene is not included in the NGS panel at this time due to presence of at least four pseudogenes. For clinicians that would like NMNAT1 analysis in the event that all other genes test negative, we request that you contact EGL directly.
- Daiger et al. (1998) Invest Ophthalmol Vis Sci 39:S295.
This test is indicated for:
- Confirmation of a clinical diagnosis of Leber congenital amaurosis.
- Carrier testing in adults with a family history of Leber congenital amaurosis.
Next Generation Sequencing: In-solution hybridization of all coding exons is performed on the patient's genomic DNA. Although some deep intronic regions may also be analyzed, this assay is not meant to interrogate most promoter regions, deep intronic regions, or other regulatory elements, and does not detect single or multi-exon deletions or duplications. Direct sequencing of the captured regions is performed using next generation sequencing. The patient's gene sequences are then compared to a standard reference sequence. Potentially causative variants and areas of low coverage are Sanger-sequenced. Sequence variations are classified as pathogenic, likely pathogenic, benign, likely benign, or variants of unknown significance. Variants of unknown significance may require further studies of the patient and/or family members.
Copy Number Analysis: Comparative analysis of the NGS read depth (coverage) of the targeted regions of genes on this panel was performed to detect copy number variants (CNV). The accuracy of the detected variants is highly dependent on the size of the event, the sequence context and the coverage obtained for the targeted region. Due to these variables and limitations a minimum validated CNV size cannot be determined; however, single exon deletions and duplications are expected to be below the detection limit of this analysis.
Clinical Sensitivity: Unknown. Pathogenic variants in the promoter region, some pathogenic variants in the introns and other regulatory element pathogenic variants cannot be detected by this analysis. Results of molecular analysis should be interpreted in the context of the patient\'s clinical and/or biochemical phenotype.
Analytical sensitivity for sequence variant detection is ~99%.
Copy Number Analysis: The sensitivity and specificity of this method for CNV detection is highly dependent on the size of the event, sequence context and depth of coverage for the region involved. The assay is highly sensitive for CNVs of 500 base pairs or larger and those containing at least 3 exons. Smaller (< 500 base pairs) CNVs and those that involving only 1 or 2 exons may or may not be detected depending on the sequence context, size of exon(s) involved and depth of coverage.
Orangene™ Saliva Collection Kit used according to manufacturer instructions. Please contact EGL for a Saliva Collection Kit for patients that cannot provide a blood sample.
Infants and Young Children (<2 years of age): 2-3 ml
Children > 2 years of age to 10 years old: 3-5 ml
Older Children & Adults: 5-10 ml
Autopsy: 2-3 ml unclotted cord or cardiac blood
Isolation using the Perkin Elmer™Chemagen™ Chemagen™ Automated Extraction method or Qiagen™ Puregene kit for DNA extraction is recommended.
Please include fundus photographs, electroretinogram (ERG) findings, visual field findings, and visual acuity, if available, for expert review and clinical correlation with test results.
- Eye Disorders: Comprehensive Sequencing and Deletion/Duplication Panels.
- Leber Congenital Amaurosis: Deletion/Duplication Panel.