[Chromosome 8 : complete trisomy and segmental trisomies]

Abstract

The phenotypic effects of trisomy of various segments of chromosome 8 have been recognized through the analysis of twelve different patients: five mosaic cases of trisomy 8, one case of trisomy for the short arm and the proximal segment of the long arm, two cases of trisomy for a portion of the short arm, and four cases of trisomy for the terminal segment of the long arm. Analysis of the data from the literature and of these personal observations allows the definition of three syndromes: trisomy 8, trisomy 8p and 8q proximal, and trisomy 8q terminal. Three clinical signs are common to the three syndromes: vertebral anomalies, depression of the mesosternum, and bulging of the forehead. This suggests that different segments of chromosome 8 carry genes affecting osseous growth. Trisomy 8p causes, in addition to severe mental deficiency, a thick nose, a large mouth, and microcephaly. Other clinical signs can be assigned to three groups corresponding to the short arm, the proximal part, and the distal part of the long arm.