"I have VHL. My nine-year-old son is therefore at 50% risk of having VHL. I took him to an ophthalmologist requesting that he be screened for VHL. The ophthalmologist checked his eyes without dilating them and assured me he did not have VHL. I questioned the accuracy of the test, since he had not dilated the eyes. He said that in young children the eyes are so clear that it is unnecessary to dilate the eyes to see the retinas and that this examination was sufficient. Is that true, or should I see another ophthalmologist?" - Ann B., Massachusetts

We sent this question to two experts in VHL:

"It is true that in young children the media of the eye are usually clear enough that the central area of the retina including the optic nerve, the macula, and the major blood vessels can be seen clearly without dilation. The peripheral areas of the retina, however, cannot be seen totally without dilation and for this reason I would recommend dilation for a baseline examination, particularly in view of the family history of VHL. Small lesions of VHL might only be able to be seen through dilated pupils and lesions in the peripheral area of the retina likewise may only be observable through dilated pupils." - Jerry Cavallerano, O.D., Ph.D., Beetham Eye Institute, Joslin Diabetes Center, Boston, MA.

"I do not think that the child had adequate screening evaluation for VHL. It is very important to perform a dilated fundus examination to adequately study the retina. I have found retinal angiomas in children's eyes as young as five years of age. It has been reported even earlier than this. Since retinal angiomas can be very tiny, one must carefully study the fundus both at the slit-lamp and with indirect ophthalmoscopy. Although the child may be free of the disease as far as the ocular examination is concerned, I would not be satisfied without a dilated examination and a very careful study." - Robert B. Welch, M.D., Associate Professor of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, Maryland.

"I agree with Dr. Cavallerano and Dr. Welch. In the Freiburg VHL study (Germany) we found the majority of retinal lesions in the periphery. Many of these patients had no central retinal angiomas. Blindness occurred mainly in childhood and youth, underscoring the need for careful investigations in young patients or relatives at risk. Yearly follow-up seems to be extremely useful in these young people. -- Hartmut P. H. Neumann, M.D., leader of the Freiburg VHL study.

Could Carpet Fumes cause VHL?

"All 8 rooms of our new home were carpeted within 2 days in December of 1973. When we moved in shortly after, we noticed odors for more than six months. I became pregnant with Tim in July of 1974 after living in the house for 8 months. Tim was born in March 1975, weighing six pounds.

"When Tim was 14 years old, our optometrist discovered a hemangioma in his right eye. An ophthalmologist suggested further investigation through CT scans of the abdomen, pelvis, spine, and brain, which led to a diagnosis of von Hippel-Lindau. Tim's two sisters, my husband and I have all had thorough CT and MRI testing which proved to be negative. They say that Tim is a 'new mutation.' Could this genetic disorder be caused by carpet fumes?" - Cindy M., Wisconsin

"You pose a very interesting question. I will ask Dr. Virginia Michels to respond. I spoke yesterday with Dr. Nina Ahmad of Wills Eye Hospital in Philadelphia, and she told me that we just don't know enough yet to say yes or no. It could be, and then again it might have nothing to do with it. It could have been any number of things, and the effect could have been on the sperm rather than the egg, since the sperm, nearer the surface of the body, are more accessible to environmental damage. The scientists are working on the genetics research to obtain better answers; meanwhile, just try not to blame yourself.

"There is a kind of randomness to genetic changes which is designed into reproduction in order to strengthen the species as we evolve, and to ensure diversity. In addition, there are simply errors which occur at a very low frequency, but with all the millions of replications it takes to make a human being, it is a miracle that there are as few errors as there are. The best example is from telecommunications. When you send data over a telephone wire, it's really a series of zeros and ones. An "A", for example, is 1000001. If 1000001 passes intact over the wire, you see an "A" on the screen. If it's 1000010, a subtle swap in one sequence, then you see a "B". If it's 100001 (dropping out only one zero) it's an exclamation point.

"The genetic code is represented as a sequence of elements represented by the letters ACGT, but it's the same principle. The VHL gene is a recipe for a protein. If the code is transferred intact, the right protein is made in the body. If something happens - a couple of letters in the code get swapped, or one drops out - then the protein is not made correctly. The intended protein did not get formed (it's not an "A") and some other protein did get formed (it's a "B").

"These errors do occur periodically and we don't understand why. It may be that Tim is the first one in the family, and it may be that one of you in fact has the flawed gene but no clinical symptoms. Since VHL has "widely variable expression," it is possible for someone to have the faulty gene and have extremely minor effects. The only truly reliable test is a DNA test.

"Your conjectures about what environmental influences might have been at work are certainly useful, we just don't know enough yet to prove or disprove it. I'll add it to the pile of conjectures from other people, and we'll see what commonalities come up. Keep those theories coming!" - Joyce Graff,
Co-Chair, VHL Family Alliance

"We have no evidence that carpet fumes or formaldehyde acts as a mutagen at this time. People working in certain medical laboratories are exposed to formaldehyde over more prolonged periods and there has never been any evidence that this causes inheritable mutations in humans." - Virginia V. Michels, M.D., Mayo Clinic, Rochester, Minnesota.

As published in the VHL Family Forum, 3:1, March 1995. For permission to reprint, please contact the VHL Family Alliance, editor@vhl.org. Further information is available from the VHL Family Alliance, info@vhl.org.