Family with three apparently balanced t(3;15) (p27;q22) translocation carriers. Association with deficits in language acquisition and mental retardation: a possible example of position effect in man.
A father, son, and daughter had a (3;15) (p27;q22) simple reciprocal translocation. No abnormality in the G-banding pattern was noted. The girl was most severely affected; she had an abnormal phenotype, noticeable delay in receptive and expressive language development, bilateral hearing impairment, and definite mental retardation. The boy had a moderate delay in receptive language skills, had moderate hearing impairment in one ear, and showed mild mental retardation. The father has low-set ears, some deficits in receptive language skills, is illiterate, and was found to be borderline mentally retarded. The mother and younger child do not have the translocation and are normal in terms of phenotype, intellect, and verbal skills. The accumulating evidence suggests that balanced translocations are associated with an increased frequency of intellectual deficit and congenital anomalies, and the cytogenetic mechanism may be that of position effect.