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2004-05-13 Answer to case of the week # 120 © Gourand www.TheFetus.net


Answer to case of the week # 120

June 4-17, 2004

Luc Druart, MD*, Hélène Dessuant, MD*, Luc Gourand, MD**, Bettina Bessières, MD***, Fernand Daffos, MD****


* Cytogénétique LCL, Paris ** Maternité Les Bluets, Paris, *** Service de Foetopahologie IPP Paris, ****Médecine Foetale, IPP, Paris

A 44 year-old patient, G2 P1,  with an unremarkable medical history. No medical history.Previous child 10 year-old, healthy. This is her 2nd pregnancy (with a different father)

First scan at 12 week, regarded as normal: nasal bone visible (not visible on this picture), NT 1,9/56 mm, Doppler DV positive “a” wave

      

An amniocentesis (for maternal age) was performed at 19 week.
The ultrasound findings included growth retardation (< 3rd percentile), ventricular septal defect, and negative ductus venosus “a” wave.

 

The cardiac anomaly ressembles a tetralogy of Fallot


Following this examination, an amniocentesis was performed which revealed an abnormal karyotype.

Cytogenetic results:

1st  cytogenetic result :

Chromosome mosaicism with a supernumerary chromosome looking like an isochromosome 21q.
In vitro chromosomal abnormality was excluded because four abnormal colonies were found in three different culture vessels.
From the cytogeneticst point of view, two dilemmas have to be resolved:

  • discrimination of the isochromosome 21q (or mosaic tetrasomy 21q) from the isochromosome 12p (or mosaic tetrasomy 12q) because photographs of these chromosomes are quite similar and mosaic tetrasomy 21q is much rarer than mosaic tetrasomy 12p

  • discrimination of “true chromosome mosaicism” and “pseudomosaicism” in which the cells with the abnormal karyotype derive from placental tissues.

In situ hybridisation (FISH) is an efficient technique for distinguishing isochromosome 21q from isochromosome 12p.
                  
Fetal blood sampling may help us to distinguish a “true chromosome mosaicism” from “pseudomosaicism”.


2nd and final cytogentic result :

Mosaic tetrasomy 21q was confirmed by FISH and the fetal karyotype was written as: 

47,XX,+i(21)(q10)/46XX

         

                 46, XX normal                                                                            tetrasomy 21q


A microdeletion in the DiGeorge chromosome region of chromosome 22 was searched because of the fetopathology findings (ie: thymus aplasia) and was excluded by FISH.

- FISH  21: 4 red spots                                            - FISH  22: red : locus q11.2; green : control

        

As the FISH technique was underway, and discussion was taking place about the opportunity of fetal blood sampling, the patient was scanned again at 21 week for control. The examination demonstrated intra uterine death with severe IUGR below 3rd percentile and fetal hydrops.

  

                                                                                                                 
Fetopathology findings: 21 trisomy dysmorphology, pulmonary atresia with ventricular septal defect (PA-VSD, the old "extreme form of Fallot"), thymus aplasia.

  

 
 

References:

1:  Dong L, Falk RE, Williams J 3rd, Kohan M, Schreck RR. Tetrasomy 12p--unusual presentation in CVS.
Prenat Diagn. 2003 Feb;23(2):101-3. PMID: 12575013 [PubMed - indexed for MEDLINE]

2:  Chen J, Shi Q, Zhang J, Li H, Zhang X, Luo J, Zhou G, Shan X, Zhang X. Detection of mosaic chromosome 21 aneuploidy in vivo with CB-FISH method.
Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 2000 Jun;17(3):196-9. Chinese. PMID: 10837524 [PubMed - indexed for MEDLINE]

3:  Soler A, Margarit E, Carrio A, Costa D, Queralt R, Ballesta F. Trisomy/tetrasomy 21 mosaicism in CVS: interpretation of cytogenetic
discrepancies between placental and fetal chromosome complements. J Med Genet. 1999 Apr;36(4):333-4. PMID: 10227405 [PubMed - indexed for MEDLINE]

4:  Lapierre JM, Cacheux V, Collot N, Da Silva F, Hervy N, Rivet D, Romana S,Wiss J, Benzaken B, Aurias A, Tachdjian G.
 Comparison of comparative genomic hybridization with conventional karyotype and classical fluorescence in situ hybridization for prenatal and postnatal
diagnosis of unbalanced chromosome abnormalities. Ann Genet. 1998;41(3):133-40.  PMID: 9833066 [PubMed - indexed for MEDLINE]

5:  Nagarsheth NP, Mootabar H. Prenatal diagnosis of mosaic tetrasomy 21q confirmed by fluorescence in situ
hybridization.Clin Genet. 1997 Apr;51(4):260-3. PMID: 9184249 [PubMed - indexed for MEDLINE]

6:  McLean S, Stanley W, Stern H, Fonda-Allen J, Devine G, Ellingham T,Rosenbaum K.  Prenatal diagnosis of Pallister-Killian syndrome: resolution of cytogenetic
ambiguity by use of fluorescent in situ hybridization.Prenat Diagn. 1992 Dec;12(12):985-91. PMID: 1287646 [PubMed - indexed for MEDLINE]

7: Gilgenkrantz S, Fryns JP, Droulle P, Schweitzer M, Chadefaux B, Prieur M. [Mosaic tetrasomy 12p. Identical nature of the Pallister syndrome, the
Teschler-Nicola/Killian syndrome and mosaic tetrasomy 21]J Genet Hum. 1987 Jan;35(1):51-61. French. PMID: 3559524 [PubMed - indexed for MEDLINE]

8:  Lopes V, Mak E, Wyatt PR. Prenatal diagnosis of tetrasomy 21.Prenat Diagn. 1985 May-Jun;5(3):233-5. PMID: 3161017 [PubMed - indexed for MEDLINE]

9:  Hall BD. Mosaic tetrasomy 21 is mosaic tetrasomy 12p some of the time.Clin Genet. 1985 Mar;27(3):284-5. No abstract available. PMID: 3987079 [PubMed - indexed for MEDLINE]

10:  Fryns JP, Petit P, Vinken L, Geutjens J, Marien J, Van den Berghe H.  Mosaic tetrasomy 21 in severe mental handicap. Eur J Pediatr. 1982 Sep;139(1):87-9. No abstract available. PMID: 7173267 [PubMed - indexed for MEDLINE]

 

 

 

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