Identification and characterization of marker

chromosome inTurner syndrome

Journal Scan

Identification and characterization of marker chromosome inTurner syndrome

R.N. Makroo a,*, Mohit Chowdhry b, Sonika Sharma c

aDirector and Sr. Consultant, Department of Transfusion Medicine, Transplant Immunology & Molecular Biology,

Indraprastha Apollo Hospitals, New Delhi, IndiabAssociate Consultant, Department of Transfusion Medicine, Transplant Immunology & Molecular Biology,

Indraprastha Apollo Hospitals, New Delhi, IndiacMolecular 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 11marker chromosomeswere 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

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0976-0016/$ e see front matterhttp://dx.doi.org/10.1016/j.apme.2013.04.002

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 agreewith the authors and strongly recommend that FISH should be done in all caseswhere amarker chromosome is

identified on chromosomal analysis so as to rule out the risk of gonadoblastoma.

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