Isochromosome 22 in trisomy 22 mosaic with five cell lines.

This report describes a full-term male infant with trisomy 22 due to an isochromosome 22. Prenatal diagnosis with amniotic fluid showed two cell lines, one with an isochromosome 22 and the other with a deleted isochromosome 22. Subsequent cytogenetic analyses of cord blood, umbilical cord tissue, and placenta revealed additional cell lines. A normal cell line was found in umbilical cord tissue and two of three placental sites. The newborn had numerous dysmorphic features and died within 48 hrs of birth.