Trisomy 8 mosaicism syndrome. Report of monozygotic twins.

Monozygotic twins were born with the phenotypical appearance of the trisomy 8 syndrome. The first twin, a stillborn, had autopsy findings suggestive of trisomy 8 syndrome. Cultured lymphocytes and skin fibroblasts of the second, liveborn twin, showed trisomy 8. While the lymphocyte culture showed 46/47, +8 mosaicism, with normal cells predominating, skin fibroblasts yielded only cells with trisomy 8. Bone marrow preparation showed only normal cells, 46,XY. Repeat lymphocyte culture at age 14 months, showed a reduced number of trisomy 8 cells. We would like to emphasize the importance of cytogenetic studies in early infancy, using both peripheral lymphocyte and skin fibroblast cultures, to increase the chance of detecting chromosomal abnormalities.