Also known as: Charcot Marie Tooth disease type 1A (CMT1A), Hereditary Neuropathy with liability to Pressure Palsies (HNPP)
Familial - Neurological
Use of test
PMP22-associated neuropathies include:
Charcot-Martie-Tooth disease type 1A (CMT1A), due to a 1.5 Mb duplication on chromosome 17 that includes the PMP22 gene
Hereditary Neuropathy with liability to Pressure Palsies (HNPP), due to a 1.5 Mb deletion on chromosome 17 that includes the PMP22 gene
This test is primarily for affected patients, for whom it provides diagnostic information. Results may have implications for family members. This test may also be offered to pre-symptomatic individuals with a family history of a PMP22-related neuropathy, with pre-test counselling by a genetics professional and written consent.
The presence of a duplication or deletion involving PMP22 would confirm a clinical diagnosis of CMT1A or HNPP, respectively. However, the absence of a detectable abnormality does not exclude a clinical diagnosis of these disorders, as point mutations are not detected by this test. Point mutations are the cause of disease in up to 5% of CMT1A cases and 20% of HNPP cases.
This test can also detect clinically significant deletions and duplications unrelated to PMP22 that may have implications for the tested patient or family members (incidental/secondary findings). The laboratory report will provide advice regarding the interpretation of such findings.
This is an assay for heritable mutations. It may raise issues of ethics or consent that are different from most other investigations ordered in the routine care of a patient. Use of the Sonic Genetics consent form (below) is not mandated, but could be used to guide the discussion with the patient.
This test can be requested by any medical practitioner.
For testing in pre-symptomatic individuals with a family history of a PMP22-related neuropathy, pre-test counselling by a genetics professional and written consent are recommended.
4 mL blood in EDTA or lithium heparin tube. Specimens may be collected by the requesting practitioner or at any Sonic Healthcare collection centre (see link below).
To help ensure the quality of the test, a genetic test should be done with a dedicated sample whenever possible i.e. a sample collected specifically for that test rather than a sample that is used for multiple tests.
We recommend that the patient or another adult check the labelling of request forms and sample tubes.