Mosaicism in trisomy 8: phenotype differences according to tissular repartition of normal and trisomic clones.

Three new observations of trisomy 8 mosaicism are presented. In two postnatal cases, both patients showed agenesis of corpus callosum associated with different clinical findings. In a third case, the prenatal diagnosis revealed trisomy 8 mosaicism exclusively in chorionic villi (CV) cells long term culture. Normal results were obtained in CV direct preparation and in cultured amniotic cells. In lymphocytes, the child showed low level trisomy 8 mosaicism. The only clinical findings were deep palmar and plantar furrows. The present cases as well as reports in the literature indicate that the variation in tissular repartition of normal and trisomic clones in trisomy 8 mosaicism is possibly responsible for the missing correlation between cytogenetic findings and clinical severity in this syndrome.