Importance of Testing/Retesting & Impact for Family
58-year-old male referred for genetic testing for retinitis pigmentosa
Suspected clinical diagnosis: Retinitis pigmentosa (RP)
Presenting complaint: Seeing low vision specialist for reduced visual acuity, both eyes
Medical history: No significant systemic medical problems
Family history: It is apparent from the pedigree chart that the retinal disease is consistent with an X-linked recessive condition
Eye exam and imaging
- Bone spicule pattern in the retina
- Visual acuity: hand motion OD; 20/200 OS
- Visual field: severely constricted—less than 5 degrees, both eyes
Additional information: Patient had prior genetic testing with an inherited retinal disease (IRD) panel (~300 genes) that identified 2 variants of uncertain significance; 1 in USH2A and 1 in WDR19
- Based on the pedigree, an X-linked cause of the disease was most likely the case. However, RPGR, the most common cause of the X-linked type of RP, was not included on the prior test
Genetic test: Retested in a different lab with the RPGR gene included on the panel
Genetic result: Positive for pathogenic variant in RPGR (c2236_2237del; p.Glu746Argfs*23)
Final diagnosis: X-linked retinitis pigmentosa (XLRP)
Key Takeaways
This patient received a prior genetic test revealing an inconclusive result because the initial genetic testing panel was not inclusive of the RPGR gene. Genetic testing panels can vary by lab,[1] further demonstrating the necessity of ensuring the inclusivity of suspected IRD genes in a genetic testing panel. With a confirmed result, the patient’s family members were recommended to perform further testing via targeted variant analysis.
OD=oculus dexter (right eye); OS=oculus sinister (left eye).
This case study is based on a licensed genetic counsellor's in-office experience. It is based on a real patient with changes made for privacy considerations.
