Non-syndromic mental retardation segregating with an apparently balanced t(1;17) reciprocal translocation through three generations

We describe a family in which non‐syndromic mental retardation (MR) and an apparently balanced reciprocal translocation, t(1;17)(p36.3;p11.2) segregates in eight individuals over three generations. Four children showed psychomotor developmental delay, reduced muscle tone, poor coordination, and learning difficulties. The affected adults had a varying range of behavioral problems and difficulties in social adjustment but no abnormal neurological signs. Most of them were functioning at the borderline learning difficulty level in intellectual abilities with additional specific difficulties in reading in two individuals. The Smith‐Magenis and 1p36.3 deletion syndromes were excluded. We propose that this reciprocal translocation has disrupted an autosomal gene with an important function in cognitive development, and this family represents a unique resource for the molecular genetic study on non‐syndromic MR. Am. J. Med. Genet. 95:99–104, 2000. © 2000 Wiley‐Liss, Inc.