Trisomy 7p resulting from isochromosome formation and whole-arm translocation.
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.
Lurie
I W
IW
Department of Pediatrics, School of Medicine, University of Maryland at Baltimore, USA.
Schwartz
M F
MF
Schwartz
S
S
Cohen
M M
MM
D000015:Abnormalities, Multiple / Q000235:genetics*; D000328:Adult; D002871:Chromosome Banding; D002874:Chromosome Mapping; D002897:Chromosomes, Human, Pair 7 / Q000235:genetics*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D018404:Isochromosomes; D007621:Karyotyping; D008297:Male; D011247:Pregnancy; D014178:Translocation, Genetic; D014314:Trisomy