How PMM2-CDG Is Diagnosed
Genetic testing is the gold standard to diagnose PMM2-CDG.
Getting a PMM2-CDG Diagnosis
Getting a diagnosis of PMM2-CDG can take a long time and be frustrating. Like other rare diseases, families often have to visit many doctors and have many tests before getting the right answer.
What families can go through to get a diagnosis:
- Seeing up to 10 different doctors
- Receiving the wrong diagnosis at first because PMM2-CDG symptoms look like other genetic or neurodevelopmental conditions
- Waiting a few months to several years to get the right diagnosis
While the journey to diagnosis can be long, if you suspect PMM2-CDG, there are specific tests you can ask your doctor about that can help provide answers.
Initial Diagnostic Tests
Doctors may suspect a congenital disorder of glycosylation (CDG) based on an evaluation of symptoms. Often the first test doctors use is called a transferrin isoelectric focusing test (TIEF). This test tells the doctor if you have altered glycosylation, but cannot confirm the specific CDG a patient may have.
Importantly, this test can give false negatives for infants less than 1-2 months old. This means it could say your child does not have a CDG when they may really have one. If you still suspect PMM2-CDG, you can ask to re-test your child or ask for genetic testing.
“The birth hospital did testing right away and said she didn’t have a CDG.
I was very nervous something was going on because she wasn’t gaining weight or hitting milestones and she had crossed eyes. She also was always sick, and I kept pressing for them to double-check or find out what was wrong with her.”
– Caregiver of Olivia, a patient living with PMM2-CDG
Confirming the Diagnosis: Genetic Testing
Doctors use genetic testing to find out exactly which type of CDG a person has. Genetic testing may be performed as the initial screening tool for PMM2-CDG or as a follow-up to a transferrin test. Providers called genetic counselors can help determine the best genetic testing option and can also help you to understand the results.
There are different ways to do genetic testing:
Single-gene testing looks only at the PMM2 gene to see if there are any changes in it. If no changes are found, doctors can do more tests to look for larger missing pieces or other affected genes.
Multigene panels test multiple related genes at the same time (eg, developmental disorders, seizure disorders). If you think you or your loved one has PMM2-CDG, double-check that PMM2 is included in the panel.
Comprehensive genomic testing looks at all genes in the body. Doctors may use this if symptoms or transferrin tests don’t give them enough clues about which specific genes to test.
Patient Spotlight
“Although the news can be hard to digest and get your head around, my husband and I (and our broader families who are incredibly supportive) have always believed that having all the cards on the table has been the best way to support us in making the best decisions for Toby. Information is power—and with an incredibly rare and inconsistent disease, any information is useful!”
– Caregiver of Toby, a patient living with PMM2-CDG