Paracentric inversion in the short arm of chromosome 1. Report of a family and review of the literature: In general, carriers of paracentric inversions are phenotypically normal, although individual reports describe like occurrence of infertility, miscarriages and mental retardation in inversion carriers. We present a family with paracentric inversion of 1 p [karyotype: 46,XX/XY, inv(1) (p13.2p36.2)] in 7 of the 12 investigated family members. The index patient, a four year-old boy, was referred for motor and mental retardation. The possible relationship between the paracentric inversion and the MR/MCA syndrome in the index patient of this family is briefly discussed.