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, 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.
