1. Introduction to the
Genetics of
Retinitis Pigmentosa
Kimberly J. Guthrie, MS CGC
Certified Genetic Counselor
Mayo Clinic
Jacksonville, FL

2. Background
 Between 1 in 3500 and 1 in 4000
individuals in the United States will
develop RP
 RP can be isolated or associated with
other medical issues as part of a
genetic syndrome

3. Inheritance
 Taking a family history can help
determine the inheritance pattern and
the risk to children and other family
members
 RP can be inherited in different ways
– Autosomal dominant
– Autosomal recessive
– X-linked

4. Genetics of RP
 At least 35 different genes have been
found to cause isolated RP
 Genetic testing is informed by
inheritance patterns
 Testing panels that test multiple genes
at once are available

5. Benefits of Genetic
Testing for RP
 Knowledge of the underlying cause
 Determine eligibility for clinical trials
 Clarify recurrence risks
 If the mutation in the gene is identified
in an individual, multiple prenatal
diagnostic options would be available

6. What to Expect: The
First Genetic Counseling
Visit
 Review of medical records including
eye doctor’s records
 Drawing out and interpreting the family
history
 Discussion of genetic testing options
including the benefits and limitations of
genetic testing
 Answer any questions you may have

7. What Happens if I have
Genetic Testing
 Usually you will have your blood
drawn for testing
– For this type of testing it doesn’t matter if
you have eaten or not
– Often we first test the person with a
diagnosis of RP and discuss testing other
relatives after test results are available
 Results are typically available within
one to two months

8. What to Expect: Results
Discussion
 If a mutation is found, the discussion
will include:
– Information about that gene
– Risks to future children and other family
members
– Discussion of clinical trials or research
studies available
– Answering any questions you may have

9. What to Expect: Results
Discussion
 If no mutation is found, the discussion
will include:
– Review of limitations of testing
– Discussion of whether additional testing
may be of benefit
– Making a plan for follow-up
– Answering any questions you may have

10. For More Information
 Genetics Home Reference
– http://ghr.nlm.nih.gov/condition/retinitis
-pigmentosa
 GeneReviews: Retinitis Pigmentosa
Overview
– http://www.ncbi.nlm.nih.gov/books/NBK1417/

11. To Schedule an
Appointment
 To schedule a Genetic Counseling
appointment at the Mayo Clinic in
Jacksonville, FL
Call (904) 953-2272