ABNORMAL MYELINATION IN A PATIENT WITH RING CHROMOSOME-18

We describe a Japanese boy with ring chromosome 18 in whom abnormal my elination was observed on magnetic resonance imaging. Cytogenetic inve stigation revealed 46, XY, r(18) (p11.2 q21.33). T-2-weighted magnetic resonance imaging scan of the brain demonstrated high signal intensit y consistent with abnormal myelination. Microsatellite marker analysis of DNA demonstrated only one copy of the myelin basic protein gene, d erived from the mother. The present case indicates that a hemizygous s tate for the myelin protein gene may be related to the abnormal myelin ation.