Mosaic trisomy 7

Abstract

Trisomy 7 mosaicism is a very rare chromosomal disorder where there is an extra copy of chromosome 7 in some of the body's cells. Most cases with this chromosomal abnormality have no clinical symptoms. The presence of abnormalities in some cases is dependent on which body cells contain the chromosomal defect. Here we report a case diagnosed incidentally, in which is raised a suspicion of trisomy 21 in fact, based on a biochemical screening test for the second quarter (triple test). Two contradictions have led us to publish this case: first, the fact that although the triple test raised the suspicion of Down syndrome with a biochemical risk calculated from 1 to 225 with a very low level of free Estriol under 0.45 MoM corrected, it turned out to be about an extremely rare mosaicism. Secondly the fact that pregnancy has stopped evolving a few days after amniocentesis, although subsequently anatomopathological examination found no fetal or placental abnormalities. We searched in the specialty literature and found very few cases described, usually diagnosed after birth at children with various congenital abnormalities, growth retardation and developmental delay. Trisomy 7 has variable expression, most common symptoms are: facial asymmetry, hypomelanosis of Ito, kidney abnormalities. In our case we identified only facial dysmorphism and severe ulnar deviation of both hands without any malformations of internal organs. Because we did not anticipate such a genetic defect and considering the fact that the pregnancy has stopped in evolution we have not performed cultures of fibroblasts and we could not determine at what level and how the fetus was genetically affected so it was impossible to speculate how it would have evolved the pregnancy and how it would have been the baby after birth.