De novo trisomy 12p in twin girls with different levels of mosaicism

Abstract

We report on a pair of twins with trisomy 12p diagnosed postnatally. The girls were referred for dysmorphism and global developmental delay and have been followed from 10 months of age. They have different levels of mosaicism for both buccal cells and lymphocytes. Although their phenotypic features were similar, there were different degrees of severity which correlate with the different levels of mosaicism.

Trisomy 12p mosaicism syndrome in a patient with hypopigmented cutaneous mosaicism and three cell lines in peripheral blood

“…8 As in our patient, in the literature, five reports of complete and mosaic trisomy 12p, presented two and three cell lines in peripheral blood lymphocytes. [3][4][5][6]9 In our patient, we detected three cell lines in peripheral lymphocytes with the additional 12p chromosome attached to chromosome 15 and chromosome X, finding not described previously.…”

“…However, only 11 patients have been described of mosaicism involving the whole short arm of the chromosome 12. [3][4][5][6][7] Duplication of 12p can occur de novo, like our patient, or it can result from chromosome segregation error of a balanced parental translocation. The variable length of the segment duplicated, the level of mosaicism and concomitant aberrations contribute to observed phenotype variability of individuals with trisomy 12p.…”

“…All patients had dysmorphic features, significantly psychomotor delay, delayed ability to walk and severe behavioural abnormalities. Other clinical features include abnormalities of the central nervous system 1,5,6 with seizures at the mean age of seven years, 1,4,5 hearing loss, 1,9 vision problems 1,9 and hypotonia 1,[3][4][5][6]9 (Table 1). Moreover, patients with mosaic trisomy 12p had lesser severe congenital anomalies, fewer feeding difficulties and lower grade of hypotonia than patients with pure trisomy 12p.…”