RPGR-related X-linked Retinitis Pigmentosa: RPGR Gene Deletion/Duplication

Condition Description

Retinitis pigmentosa (RP) is a group of inherited disorders characterized by abnormalities of the photoreceptors on the retinal pigment epithelium.  RP disorders lead to progressive visual loss.  The first symptom is usually night blindness followed by visual field constriction which eventually leads to central vision loss.  Isolated RP is most often inherited as an autosomal recessive disorder (50-60% of cases), but can be autosomal dominant (30-40%), or X-linked (5-15%) as well.  More than 45 different genes accounting for approximately 60% of affected individuals have been implicated in RP. 

Mutations in RPGR (Xp21.1), also called RP3, account for 70-90% of X-linked RP cases.  Carrier females may show mild retinal degeneration.
Mutations in RPGR have also been identified in individuals with cone-rod dystrophy, RP with sinorespiratory infection, with or without deafness, and atrophic macular degeneration. 

For patients with suspected X-Linked RP, sequence analysis is recommended as the first step in mutation identification. For patients in whom mutations are not identified by full gene sequencing, deletion/duplication analysis is appropriate.

This testing is for analysis of the RPGR gene only.

Visit www.ThinkGenetic.com for patient-friendly information on retinitis pigmentosa.

References

  • Hartong, D. et al.  Retinitis pigmentosa Lancet. 368:1795-7809.
  • GeneReviews
  • OMIM #312610RPGR gene
  • OMIM #300029RP3 gene

Genes (1)

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Indications

This test is indicated for:

  • Confirmation of a clinical diagnosis of RPGR-Related X-Linked RP in an individual in whom sequence analysis was negative.
  • Carrier testing in adults with a family history of RPGR-Related X-Linked RP in whom sequence analysis was negative.

Methodology

DNA isolated from peripheral blood is hybridized to a CGH array to detect deletions and duplications. The targeted CGH array has overlapping probes which cover the entire genomic region.

Detection

Detection is limited to duplications and deletions. The CGH array will not detect point or intronic mutations. Results of molecular analysis must be interpreted in the context of the patient's clinical and/or biochemical phenotype.

Specimen Requirements

When sample fails to meet the acceptable criteria, please call 470.378.2200 and ask to speak with a laboratory genetic counselor (eglgc@egl-eurofins.com).
Submit only 1 of the following specimen types
Whole Blood (EDTA)
WBP

Requirements
EDTA (Purple Top)
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
Collection and Shipping
Ship sample at room temperature for receipt at EGL within 24 hours of collection. Do not refrigerate or freeze.
DNA, Isolated
DNA

Requirements
Microtainer
3µg
Isolation using the Perkin Elmer™Chemagen™ Chemagen™ Automated Extraction method or Qiagen™ Puregene kit for DNA extraction is recommended.
Collection and Shipping
Refrigerate until time of shipment in 100 ng/µL in TE buffer. Ship sample at room temperature with overnight delivery.
  • Sequence analysis of the RPGR gene is available and is required before deletion/duplication analysis.  
  • Custom diagnostic mutation analysis (KM) is available to family members if mutations are identified by targeted mutation testing or sequencing analysis.
  • Prenatal testing is available only for known familial mutations to individuals who are confirmed carriers of mutations. Please contact the laboratory genetic counselor to discuss appropriate testing prior to collecting a prenatal specimen.
  • Sequencing analysis for the RP2 gene is also available.

How to Order