MARSHALLS GENETIC DEFECT UNLIKELY CAUSED BY RADIATION

admin's picture

Two Waardenburg’s Syndrome kids get attention

MAJURO, Marshall Islands (Yokwe, June 20, 2009) – There has been attention in recent years to the appearance of an unusual birth defect syndrome in at least two children born to parents living in the northern Marshall Islands. This medical disorder has been diagnosed by physicians in Hawaii as Waardenburg’s syndrome. Waardenburg’s syndrome is a well known to physicians as a syndrome that includes patches of light colored hair, hearing defects, changes in the pigmentation of the eyes, and other characteristic features. It may occasionally be associated with cleft lip or palate, a gastrointestinal disorder called Hirschprung disease that can cause intestinal blockage, and abnormal development of the limbs. Unfortunately, some affected children may die prematurely.

The syndrome was named after the Dutch Physician who fi rst described it in 1951. There are actually several diff erent manifestations of this syndrome that have been identifi ed subsequently. There are now at least four types of Waardenburg’s syndrome and several sub-types. Its appearance can be highly variable; some individuals may have all or just a few of the features.

In most cases the syndrome is inherited in an autosomal dominant pattern, meaning that it only takes one inherited gene from either of the parents for the child to be affected.

In this case, one of the parents usually has some signs of the disease. Some forms of Waardenburg’s syndrome are autosomal recessive, meaning that genes would have to be inherited from both parents. In this case, the parents usually have no signs of disease. In either situation, it is possible for a family to have more than one child with the Waardenburg’s syndrome. While the information is incomplete, it appears that the Marshall Islands cases are probably of the second (recessive) type.

Waardenburg’s syndrome is not common in the general population, occurring in only one out of about 42,000 births. The frequency can be higher in some population groups. But in schools for the deaf, typically 2-3% of the students have this condition, so it is a common cause of deafness. All races and sexes appear to be affected equally. The disease has been recognized in many parts of the world.

The genes that control the syndrome have also been identified and genetic testing can be done. Unfortunately, there is no specific treatment or cure. Genetic counseling is available to assist parents of a Waardenburg’s syndrome child to understand their risk for having another affected baby. The question of whether there could be a connection between radiation exposure and Waardenburg’s syndrome deserves some discussion. This question has two parts.

First, there is the issue of exposure to the parents. No heritable birth defects from radiation exposure have ever been observed in humans. More specifically, the National Research Council found no statistically demonstrable adverse genetic effects attributable to radiation exposures sustained by the (Japanese) survivors and no significant adverse effects in more than 30,000 progeny from parents who received low doses of radiation.

Similarly, the International Commission on Radiological Protection (ICRP) says that up to the time a child is conceived, radiation exposure to the testes and ovaries of either parent has not been shown to cause birth defects in children. Although there is no proof of radiation induced inherited genetic defects in humans, some animal studies do show that inherited genetic defects may result from experimental radiation exposure. Based on animal data, current risk estimates to grandchildren of persons exposed to radiation represents 0.4 to 0.6% of the natural incidence of

The second part of this question is whether it is possible for direct radiation exposure to a pregnant woman to cause the Waardenburg‘s syndrome. There are no cases of Waardenburg’s syndrome caused by radiation exposure reported in the medical literature.

In addition, scientists think that the threshold for fetal malformations is 100-200 mGy of radiation to the fetus during pregnancy, which would be an unusually high dose for a pregnant woman to receive given the current data about levels of radiation exposure in the Marshall Islands. Receiving 100 – 200 mGy of radiation is the equivalent to obtaining three CT scans or 20 conventional x-rays. Based on current medical and scientific data a connection between Waardenburg’s syndrome and radiation exposure in the Marshall Islands is very unlikely.

--from Lawrence Livermore National Laboratory, Dr. James Seward and Dr. Terry Hamilton, Marshall Islands Monitor, Vol. 1, Number 1

Yokwe: http://www.yokwe.net/

Rate this article: 
Average: 4 (1 vote)

Add new comment