CAG repeat contraction in the androgen receptor gene in three brothers with mental retardation

We report on three brothers with mental retardation and a contracted CAG re peat in the androgen receptor (AR) gene, It is known that expansion of the CAG repeat in this gene leads to spinal and bulbar muscular atrophy (SBMA o r Kennedy disease); however, contracted repeats have not yet been implicate d in disease. As the range of the length of CAG repeats in the AR gene, lik e those of other genes associated with dynamic mutations, follows a normal distribution, the theoretical possibility of disease at both ends of the di stribution should be considered. Am. J. Med. Genet. 85:209-213, 1999. (C) 1 999 Wiley-Liss, Inc.