Maternal isodisomy of chromosome 9 with no impact on the phenotype in a woman with two isochromosomes: i(9p) and i(9q).

We describe a 34-year-old healthy woman with isochromosomes for the short and long arm of chromosome 9 who was ascertained because of repeated spontaneous abortions. Molecular analysis demonstrated maternal uniparental isodisomy for the whole chromosome 9, thus the origin of the isochromosomes was maternal. Because the patient had a normal phenotype, the maternal isodisomy supports the previous assumption that there are no maternally imprinted genes on chromosome 9. Copyright 1999 Wiley-Liss, Inc.