American Journal of Medical Genetics 44842 (1992)

Letter to the Editor Thanatophoric Dysplasia in Monozygotic Twins Discordant for Cloverleaf Skull: Prenatal Diagnosis, Clinical and Pathological Findings To the Editor: Corsello et al. [1992] reported the above-mentioned case recently. Although it seems quite likely that the twins were monozygotic (MZ), there is no acceptable proof of this in the report. Studies of discordance for developmental disorders in MZ twins are very valuable, provided th at full documentation of zygosity is documented. At present, the following criteria could be used: 1. Unlike-sex twins are most probably dizygotic, except when there is heterokaryotypia for the Y chromosome in MZ twins, as in the cases reported by Dallapiccolaet al. [19851,Gonsoulin et al. [19901, andPerlman et al. [19901; 2. Conjoined twins are MZ; 3. Monochorionic (MC) twins are almost all MZ,but a few cases are converted from dichorionic (DC) to MC placentation [Megory et al., 19911; 4. Although zygosity has previously been determined in like-sex DC twins by analysis of multiple gene products, the definitive method now involves restriction fragment length polymorphisms [Hill and Jeffreys, 1985; Derom et al., 1985, 1991; Kovacs et al., 1988; Azuma et al., 1989; Porrini et al., 1990; Machin, 1990; Akane e t al., 19911.

Many papers in this journal have documented satisfactorily the zygosity of reported twins; indeed, the journal has contributed to knowledge about the etiology of MZ twins LLupski et al., 19911. It would seem optimal for authors and editors to adhere to acceptable standards for the reporting of findings relating to twin zygosity. The criteria listed above would satisfy this need.

REFERENCES Akane A, Matsuara K, Shiono H, Yamada M, Nakagone Y (1991): Diagnosis of twin zygosity by hypervariable RFLP markers. Am J Med Genet 41:96-98. Azuma C, Kamiura S, Nobunaga T, Negoro T, Saji F, Tanizawa 0 (1989): Zygosity determination of multiple pregnancy by deoxyribonucleic acid fingerprints. Am J Obstet Gynecol 260:734-736.

Received for publication February 11, 1992, Address reprint request to Dr. Geoffrey Machin, Department of Pathology, University of Alberta, Edmonton, Alberta, Canada

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0 1992 Wiley-Liss, Inc.

Corsello G, Maresi E, Rossi C, Guiffre L, Cittandini E (1992): Thanatophoric dysplasia in monozygotic twins discordant for cloverleaf skull: Prenatal diagnosis, clinical and pathological findings. Am J Med Genet 42:122-126. Dallapiccola B, Stomeo C, Ferranti G, Di Lecce A, F'urpura M (1985): Discordant sex in one of three monozygotic triplets. J Med Genet 22:6-11. Derom C, Bakker E, Vlietinck R, Derom R, Van den Bergh H, Thiery M, Pearson P (1985):Zygosity determination in newborn twins using DNA variants. J Med Genet 22:279-282. Derom C, Vlietinck R, Derom R, Boklage C, Thiery M, Van den Berghe H (1991); Genotyping of macerated stillborn fetuses. Am J Obstet Gynecol 164:797-800. Gonsoulin W, Copeland KL, Carpenter RJ, Hughes MR, Elder FFB (1990): Fetal blood sampling demonstrating chimerism in monozygotic twins discordant for sex and tissue karyotype (46,XY and 45,X).Prenat Diagn 10:25-28. Hill AVS, Jeffreys AJ (1985): Use of minisatellite DNA probes for determination of twin zygosity at birth. Lancet ii:1394-1395. Kovacs B, Shahbahrami B, Platt LD, Comings D (1988): Molecular genetic prenatal determination of twin zygosity. Obstet Gynecol 72954-956. Lupski JR, Garcia CA, Zoghbi HY, Hoffman EP, Fenwick RG (1991): Discordance of muscular dystrophy in monozygotic female twins: Evidence supporting asymmetric splitting of the inner cell mass in a manifesting carrier of Duchenne dystrophy. Am J Med Genet 40:354-364. Machin GA (1990): Definitive methods of zygosity determination in twins: Relevance to problems in the biology of twinning. Acta Genet Med Gemellol 39459-471. Megory E, Weiner E, Shalev E, Ohel G (1991): Pseudomonoamniotic twins with cord entanglement following genetic funipuncture. Obstet Gynecol 78:915-917. Perlrnan E J , Stetten G , Tuck-Muller CM, Farber RA, Neuman WL, Blakemore KJ, Hutchins GM (1990):Sexual discordance in monozygotic twins. Am J Med Genet 37:551-557. Porrini SC, Sciarra A, Sulli N, Piane M, Gualtieri R, Del PortoG (1990): Variable number of tandem repeats in zygosity diagnosis in twins. Acta Genet Med Gemellol39473-477.

Geoffrey A. Machin Department of Pathology University of Alberta Edmonton, Alberta, Canada

Thanatophoric dysplasia in monozygotic twins discordant for cloverleaf skull: prenatal diagnosis, clinical and pathological findings.

American Journal of Medical Genetics 44842 (1992) Letter to the Editor Thanatophoric Dysplasia in Monozygotic Twins Discordant for Cloverleaf Skull:...
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