Last modified on Monday, February 25 2013.
Courtesy of Dr. Mark Cohen
This unfortunate young boy died when he was 8 years old. Gross examination demonstrated diffuse cerebral myelin loss. His parents have just found out they are pregnant, and that the fetus is female. What is the likelihood that she will also develop white matter degeneration?
The pathological features are consistent with juvenile onset adrenoleukodystrophy, which is an X-linked disorder. In the absence of additional chromosomal abnormalities (XO), the chance of his sister developing the same disease is negligible. (
A 50% risk is characteristic of autosomal dominant disorders, although these diseases often demonstrate variable expression and penetrance. (
Autosomal recessive leukodystrophies, such as metachromatic leukodystrophy and globoid cell leukodystrophy/Krabbe disease would be expected in approximately 25% of offspring regardless of sex. (
Greater than 50% risks are rarely encountered, but may be seen in male siblings of probands with diseases encoded by mitochondrial DNA (