A non-sex chromosome marker in a patient with an atypical Ullrich-Turner phenotype and mosaicism of 46,X,mar/46,XX

The absence of a sex chromosome in conjunction with the presence of a marke r chromosome generally implicates a sex chromosome origin for such marker c hromosomes. These types of findings are frequently associated with Ullrich- Turner syndrome. We report a patient that presented with an atypical Ullric h-Turner phenotype and a cytogenetic mosaicism of 46,X,mar/46,XX. The marke r chromosome was derived from chromosome 20, not from the X or Y chromosome , The patient's clinical features are described and discussed relative to t he cytogenetic findings. This case further demonstrates the necessity of ma rker chromosome identification for accurate phenotype - karyotype correlati on.