Trisomy 7p resulting from isochromosome formation and whole-arm translocation

Am J Med Genet. 1995 Jan 2;55(1):62-6. doi: 10.1002/ajmg.1320550117.


A newborn boy with a large anterior fontanel, minor facial anomalies, postaxial polydactyly, patent ductus arteriosus, and developmental delay had trisomy of 7p due to an i(7p) and a concomitant t(2;7) (q37.3;q11.1). Significant enlargement of the fontanel is the most characteristic finding in most patients with duplications involving 7p15-pter. Asynchrony in fore- and hindbrain and hemisphere formation leading to brain asymmetry and various defects in the posterior fossa are typical of infants with duplications of 7p11-p12. A variety of heart defects has also been found in more than 50% of patients with duplication of 7p segments. Isochromosome formation accompanied by whole-arm translocation, resulting in uniparental isodisomy for the involved segment, is an extremely rare cause leading to partial trisomies. Although it is not clear whether isochromosome formation precedes the whole-arm translocation or follows it, the secondary rearrangement may have adaptive significance.

Publication types

  • Case Reports
  • Review

MeSH terms

  • Abnormalities, Multiple / genetics*
  • Adult
  • Chromosome Banding
  • Chromosome Mapping
  • Chromosomes, Human, Pair 7 / genetics*
  • Female
  • Humans
  • Infant
  • Infant, Newborn
  • Isochromosomes*
  • Karyotyping
  • Male
  • Pregnancy
  • Translocation, Genetic*
  • Trisomy*