Agenesis of the corpus callosum with mosaicism 46,XY/47,XY, extra ring chromosome.

A case of agenesis of the corpus callosum with a chromosomal abnormality is reported. The patient was a male infant, born to phenotypically normal, non-consanguineous parents. He had an abnormal phenotype, mental retardation, and chromosome mosaicism 46,XY/47,XY,+r. Chromosomal analysis of both parents showed a normal karotype. The origin of the small ring chromosome could not be determined and it is difficult to relate the phenotype of the infant to the cytogenetic findings.