Humangenetik 22, 59--65 (1974) © by Springer-Verlag 1974 Kurze Originalmitteilungen • Short Communications Communications br~ves Partial Trisomy 11 in a Child Resulting from a Complex Maternal Rearrangement of Chromosomes 11, 12 and 13" Otto Sanchez, Jorge J. Yunis, and Javier I. Escobar Medical Genetics Division, Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis Received October 1, 1973 / December 12, 1973 Summary. A complex structural rearrangement of chromosomes 11, 12 and 13 was found in a normal female who gave birth to an affected child with partial trisomy for the short arm of chromosome 11 and a balanced translocation 12/13. The detailed analysis of the G-banded chromosomes from early metaphases permitted the delineation of new chromosomal bands which in turn proved essential to the identification of this unusual phenomenon. Zusammen]assung. Bei einer normalen Frau, die ein Kind mit partiellcr Trisomie des kur- zen Armes des Chromosoms 11 und eine balaneierte Translokation 12/13 hatte, wurde ein kompliziertes strukturelles Rearrangement der Chromosomen 11, 12 und 13 gefunden. Eine detaillierte Analyse dcr Chromosomen nach Darstcllung der G-Banden aus fr/ihen Metaphasen erlaubte die Abgrenzung neuer Chromosomenbanden, die sich ihrerseits als notwcndig for die Analyse dieses seltenen Ph~nomens erwiesen. Introduction The recent development of the chromosome banding techniques by means of which each one the human chromosomes is amenable to detailed analysis, has broadened the field of cytogenetics. In this way, new syndromes, the result of duplication or deficiency of specific chromosomal segments, are being uncovered. In this report, a case that was not possible to solve with the use of the standard chromosome technique has been revisited in an attempt to characterize the events that led to an unusual karyotype in a phenotypically normal mother and in her affected child. The application of the G-banding techniques to early metaphases made possible to identify a complex phenomenon of chromosomal rearrangement involving chromosomes 11, 12 and 13 in the mother, and a partial trisomy for the short arm of the chromosome 11 accompanied by a balanced translocation 12/13 in the child. A comparison was made between the proband's phenotype and a similar patient recently reported in the literature. Case Report S. G. was a 3-year-old girl, the full term product of an uncomplicated pregnancy and delivery. She was admitted for the first time at the University of Minnesota Hospitals at the age of 2 months for evaluation of congenital defects. At that time she was noted to be small, * This work was partly supported by research Grant No. HD-01962 from the National Institutes of Health.