Objectives: There are suggestion, that Turner syndrome (TS) patients with mosaic karyotype for a Y-DNA-containing cell line are at risk of Y-induced gonadoblastoma. The TS patients in whom some or all cells contain a marker chromosome of unknown origin and those in whom there is clitoromegaly or other evident virillisation should be tested by FISH or PCR techniques.
Design: The aim of our study to present a TS girl with mosaic karyotype and marker chromosome, which origin from X chromosome was detected by FISH method.
Material and methods: 5-years old girl in whom TS was established. Clinical analysis included the full dysmorphic and clinical phenotype of TS. Chromosome analysis was performed on peripheral blood samples using routine cytogenetic methods and FISH technique.
Results: Clinical examination of girl showed many typical signs of TS besides of normal weight and length at birth and not typical for TS patients heart defect. First routine chromosome analysis, at age of 6 month, showed only 45,X cell line, Second study revealed mosaic karyotype with marker chromosome. FISH analysis for interphase nuclei and metaphase chromosomes using X centromere probe explained origin of marker from X chromosome. The karyotype was 45,X[155]/46,X,+mar[8].fish mar(X)(DXZ1+).
Conclusion: Presence of marker chromosome in karyotype of patient with TS may modify their phenotype and it is a indication for molecular examination by FISH technique.