Abnormal skin fibroblast karyotypes in two dysmorphic patients with normal lymphocyte chromosomes

Abstract

Although mosaicism for chromosomal abnormalities in lymphocyte cultures is common, apparent restriction to one tissue is unusual. A female patient with phenotypic features suggestive of chromosomal disorder, but with a normal lymphocyte karyotype was found to have a cytogenetic aberration in skin fibroblast karyotypes - 46,XX/47,XX, + 20 (30%/70%). Her phenotype will be described in detail. Another patient with a phenotype slightly resembling Down’s syndrome and having a normal karyotype in lymphocytes exhibited a marker chromosome in all cells derived from skin fibroblasts. The marker is a product of a tandem translocation between chromosomes 1 and 5. The additional genetic material is the short arm of chromosome 1. We have considered whether the chromosome changes limited to fibroblast cultures could represent artifacts to long-term culture conditions or could possibly be a consequence of X-ray therapy (as in the case of the second patient).