How is VHL Diagnosed?
Early diagnosis is the key to the providing people living with VHL disease with the best care and most effective treatment. When there is a known family history, it is important to conduct DNA testing as soon as possible to determine if the patient has VHL disease, regardless if the person currently has a tumor or presents with symptoms.
If there is a positive DNA diagnoses of VHL, it is important to begin surveillance testing early before any symptoms occur, if possible. Most VHL lesions are easier to treat when they are small. Detection of affected individuals by DNA analysis of a blood sample is now possible for nearly all VHL families. The accuracy of the testing and its usefulness in most families is increasing rapidly. DNA testing can be used to determine which members of the family need to be followed closely. It can also determine which members may be reassured that they they do not carry the VHL gene mutation.
If genetic testing is not yet available for a suspected VHL mutation, an individual may be clinically diagnosed, based on the onset of symptoms (ie. detected lesions), and will need to continue with regular medical screening. One set of normal results or findings does not necessarily mean there is no VHL present, since the first evidence of VHL may occur later in life. Occasionally a person may be so mildly affected that VHL may seem to skip a generation. VHL has been diagnosed for the first time in people as old as 80, often because their children or grandchildren developed VHL tumours.
Eighty percent of individuals affected by VHL have inherited the mutated tumor suppressor gene, with a fifty percent chance of passing that mutated gene to their offspring. The remaining twenty percent of those with VHL are a result of a spontaneous mutation, or a mosaic presentation. Genetic diagnosis is more complex as the VHL mutation may be absent from blood and the genetic test can be falsely negative.