To analyze the karyotypes of 11 cases of Turner syndrome with marker chromosome, and study the phenotypic effects resulting from the abnormal karyotype.

1. Identification and
characterization of marker
chromosome in
Turner syndrome

2. Journal Scan
Identification and characterization of marker chromosome in
Turner syndrome
R.N. Makroo a,
*, Mohit Chowdhry b
, Sonika Sharma c
a
Director and Sr. Consultant, Department of Transfusion Medicine, Transplant Immunology & Molecular Biology,
Indraprastha Apollo Hospitals, New Delhi, India
b
Associate Consultant, Department of Transfusion Medicine, Transplant Immunology & Molecular Biology,
Indraprastha Apollo Hospitals, New Delhi, India
c
Molecular Biologist, Department of Transfusion Medicine, Transplant Immunology & Molecular Biology,
Indraprastha Apollo Hospitals, New Delhi, India
Available online 25 May 2013
Comments
Turner’s syndrome and mixed gonadal dysgenesis may compose a spectrum extending from 45, X monosomy with absent or
undetectable Y-chromosome DNA and bilateral streak gonads to a 45, X/46, XY karyotype with a male phenotype and dysgenetic
testes. In routine karyotype analysis, a marker chromosome may be present which can originate from X/Y or non sex chromo-
some. Presence of marker chromosome in karyotype of patient with Turner syndrome may modify their phenotype and it is an
Identification and characterization of marker chromosome in Turner syndrome. Tan YQ, Cheng DH, DI YF, Li LY, Lu GX.
Zhonghua Fu Chan Ke Za Zhi. Oct 2007;42(10):679e682.
Abstract
Objective: To analyze the karyotypes of 11 cases of Turner syndrome with marker chromosome, and study the phenotypic
effects resulting from the abnormal karyotype.
Methods: Eleven Turner syndrome patients had a mosaic karyotype and carried a marker chromosome, and 6 marker
chromosomes were ring chromosomes. Their karyotypes were showed as mos. 45, X/46, X, þmar or mos. 45, X/46, X, þr.
Fluorescence in situ hybridization (FISH) technique with X/Y centromere probes was performed to determine the origin of
the marker chromosome. Reverse chromosome painting technique was used to identify the breakpoints of two largest
markers. Phenotype effects with different chromosome breakpoints were compared.
Results: All the 11 marker chromosomes were ring X chromosomes. The breakpoints of the r(X) were involved in Xp22, Xq22,
Xq24 and Xq26, etc.
Conclusions: The marker chromosomes in Turner syndrome mainly originate from X chromosome and form ring chro-
mosome X. Each r(X) in our patients was mosaic, indicating it was originated from mitosis error during early embryo
development. To analyze the origin of the marker chromosome and the breakpoint of r(X) will provide guidance for the
therapy and prognosis of the Turner syndrome patient.
* Corresponding author.
E-mail address: makroo@apollohospitals.com (R.N. Makroo).
Available online at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/apme
a p o l l o m e d i c i n e 1 0 ( 2 0 1 3 ) 1 7 1 e1 7 2
0976-0016/$ e see front matter
http://dx.doi.org/10.1016/j.apme.2013.04.002

3. indication for molecular examination by FISH technique. Also, if the origin of marker chromosome is Y, the patient is at risk of
developing gonadoblastoma. The risk of gonadal tumors, extent of virilization, and degree of male differentiation may depend
both on the proportion of Y-chromosome-bearing cells and on the specific segment of the Y chromosome that is present.
In our setting, a 14-year-old female was referred to us with severe growth retardation, primary amenorrhea, poor
development of secondary sexual characteristics, web neck, increased FSH and LH. A provisional diagnosis of Turners
syndrome was made clinically. On chromosomal analysis two cell lines were detectable. First cell line revealed 45, X.
However, second cell line revealed 46, X, þmar.
FISH test was performed for marker chromosome to rule out the presence of Y chromosome so as to delineate the risk of
gonadoblastoma in the patient. The marker chromosome identified in the chromosomal analysis was found to be centro-
meric part of X chromosome on FISH analysis, thus ruling out the Y chromosome and the risk of gonadoblastoma.
We fully agree with the authors and strongly recommend that FISH should be done in all cases where a marker chromosome is
identified on chromosomal analysis so as to rule out the risk of gonadoblastoma.
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