Trisomy 13 mosaicism demonstrated only in skin fibroblasts in a patient presenting psychomotor retardation, pigmentary dysplasia and some dysmorphic features

Abstract

A Brazilian female infant presented delayed psychomotor development, skin pigmentary dysplasia and some dysmorphic features. Chromosome analysis from peripheral blood culture was normal, but the karyotype from skin fibroblasts revealed mosaicism for trisomy 13. This case demonstrates the relevance of performing chromosomal analysis of skin fibroblasts in patients with mental retardation, associated with pigmentary dysplasia of the skin and a normal karyotype in peripheral blood lymphocytes. To our knowledge, it is the first report of trisomy 13 demonstrated only in skin fibroblasts

Importância da análise cromossômica dos fibroblastos em casos suspeitos de mosaicismo: experiência de um serviço de Genética Clínica

“…The skin is usually used because of its accessibility (2) . Chromosome abnormalities in the fibroblasts of people with phenotypical abnormalities but normal lymphocytes have been described, and this was the case of our patients with trisomy 22 in mosaic (1,4,20) . It would appear logical to take the biopsy from the abnormal region, which is generally an area of abnormal pigmentation or growth and which is what was done with our patients; but the abnormal cells are often found in fibroblasts cultured from both normal and abnormal skin (1,17) .…”

“…Furthermore, it is important that physicians be aware of the spectrum of clinical findings that chromosomal mosaicism can cause (1) . As Hall (1988) (12) and Ferreira et al (1996) (4) have pointed out, findings such as abnormal pigmentation following Blaschko's lines and body asymmetry are clues suggestive of mosaicism.…”

“…However, there are very few laboratories in Brazil with the infrastructure and technical capacity necessary to conduct this type of analysis. Furthermore, there is a paucity of studies of the subject in our country and those that do exist are basically descriptions of case histories (4)(5)(6) .…”

Confirmation of mosaic trisomy 22 in an infant with failure to thrive

“…When available, comparative genomic hybridization is the preferred method of diagnosis 14 as its positive yield is higher than with conventional karyotyping. In addition, the use of a buccal cells 15 or fibroblasts 16 for testing is more likely to identify the abnormality.…”