I have a child born with two different colored eyes. He is now deaf in one ear and the other ear is going deaf. Can you give me some information about whether these might be connected in some way? The doctors want to do DNA and other testing, but can you at least give me a name for this thing?

M.C.

The folks who specialize in this area are known as medical geneticists. These specialists are trained to recognize subtle abnormalities of the eyes, face, teeth, hands, feet and so forth, and they are able to "put it all together" and recognize whether this constellation of abnormalities corresponds to a known syndrome. Such specialists are also referred to as dysmorphologists; dysmorphology is the study of abnormal form.

I have a pretty strong hunch as to your son's diagnosis, but only a medical geneticist could answer your question with any degree of certainty. This would be after (1) obtaining a family history, (2) examining your son and (3) performing DNA tests. Then and only then could the medical geneticist determine your son's diagnosis. With the limited information you have provided, I can only make an educated guess ... and that guess would be that your son has Waardenburg syndrome.

Now, "syndrome" has a very specific meaning to a doctor, but the word tends to be used very loosely by the lay public to mean "a collection of abnormalities that usually occur together." Such a collection is more properly referred to as a sequence. In contrast, a syndrome is best defined as "a collection of abnormalities that occur together, owing to one single causal factor." This is not trivial semantics. An understanding of causation is vitally important for several reasons:

• Very often, prognosis -- determining what the future holds for this child, in terms of health problems, life expectancy and so forth -- is possible for syndromes, and is more difficult for sequences.
  
• If we understand the cause of a given syndrome, we may be able to devise rational treatments for the medical problems that arise within that syndrome.
  
• In the case of genetic syndromes, if we understand which gene is at fault, DNA testing may be available. Some parents would want to know if their next child will have the same syndrome. Since this sort of testing can be done during pregnancy, the parents would then have the option of terminating the pregnancy or planning for the needs of a disabled child. Also, when your son grows up, he will want to know, "What are the chances that a child of mine will have this syndrome?" If the cause is known, then this question is answerable.
  

In the case of genetic syndromes, the answer to this last question will vary depending on the specific genetics. This is an oversimplification, but in general, syndromes may be dominant, recessive or sex-linked. A syndrome prompted by a dominant gene has a 50 percent chance of appearing in each of the patient's children (and the chance is greater if the patient's spouse or both the patient's parents have the syndrome as well). If the syndrome comes from a recessive gene, the patient's children will not develop the syndrome if the other parent does not carry the same gene, but the risk rises to 100 percent if the patient's spouse has the same syndrome, and to 50 percent if the spouse carries the recessive gene. Sex-linked syndromes will be passed only to 50 percent of male children, and are passed only from mother to son. The explanation for these numbers is fairly simple, but is way beyond the scope of this Q&A.

You may have noticed that I have not described Waardenburg syndrome. That's because I would rather not be the source of alarming disinformation if my "stab in the dark" happens to be wrong. Once your son has been appropriately diagnosed with a specific disorder, that's the time to get more information.