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Inherited Disorders and Birth Defects

46th Chromosone

07/07/2006

Question:

A friend of mine has a short arm 46th X chromosone. He is a male. Age 17 and mentally challenged. Little short term memory but good long term memory. Can not read or write, keeps to himself quite often. Is this information sufficient to indicate a condition, and if so what would the name be so that i may be able to read more about it. The sister (18) is deaf, otherwise normal. No known genetic conditions in the family from the mothers side for quite a number of generations back. Many thanks in advance.

Answer:

It sounds like you are describing a deletion (loss) of chromosomal material from the X chromosome.

Any time there is a loss of chromosomal material there are almost always problems. The types of problems seen depend on the location and length of the deleted chromosomal material. The location and length of the deletion also tells us which genes have been deleted. Mental retardation and cognitive problems are almost always present and there may be other physical abnormalities as well.

It is not possible to provide a specific name beyond, deletion of Xp (loss of genetic material from the short arm of the X chromosome), unless you know the exact location and size of the loss. Deafness in the sister is probably not related to her bother’s chromosome abnormality; however, she should be evaluated. While these types of chromosomal problems usually do not run in families, parents usually have their chromosomes examined to rule out the possibility of a translocation (chromosomal material that is all present, but has been rearranged).

If the family has not been seen by a geneticist or genetic counselor, I would highly recommend that they do so. The family can locate a genetics center near them through the National Society of Genetic Counselors’ website below. More information about chromosomal abnormalities can be found at the Chromosome Deletion Outreach website below.

Related Resources:

National Society of Genetic Counselors Resource Center
Chromosome Deletion Outreach

For more information:

Go to the Inherited Disorders and Birth Defects health topic, where you can:

Response by:

Anne   Matthews, RN, PhD Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University