The changing phenotype in diploid/triploid mosaicism may mimic genetic syndromes with aberrant genomic imprinting: follow up in a 14-year-old girl.

Diploid/triploid mosaicism is a rare chromosome aberration characterized by growth and mental retardation, muscular hypotonia, clinodactyly, syndactyly of fingers and toes, asymmetry of the body and the face, truncal obesity, and pigmentary anomalies of the skin. Many patients initially present with severe growth retardation and develop truncal obesity later in life. Variable phenotype expression during development and restriction of triploid cells to certain tissues explain why the diagnosis of diploid/triploid mosaicism is often delayed. Here, we report on a moderately retarded 14-year-old girl with diploid/triploid mosaicism due to inclusion of the second polar body, whose changing phenotype overlaps considerably with different genetic disorders associated with aberrant genomic imprinting. The observation that triploid cells, which in our patient show remarkably variable distribution in different tissues, may also be present in easily accessible tissues such as urinary sediment or buccal smear may contribute to an earlier diagnosis of this rare syndrome.