Trisomy 18 mosaicism in two siblings

Abstract

Two siblings are presented displaying low Girth weight, marked microcephaly, severe mental and growth retardation, and convulsive disorder. Leukocyte and fibroblast cultures showed two cell lines, 46/ 47 ,+ 18 , The extra E group chromosome in 30 to 40% of the cells was identified as No. 18 by Q‐banding and G‐banding techniques.