Helga Rehder

Cytogenetic analyses of culture failures by comparative genomic hybridisation (CGH)-Re-evaluation of chromosome aberration rates in early spontaneous abortions.

Comparative genomic hybridisation (CGH) represents an alternative molecular-cytogenetic technique capable of detecting chromosomal imbalances by reverse fluorescence in situ hybridisation. As the technique uses genomic DNA for assessment it does not rely on metaphase chromosomes in the test material and thus circumvents technical problems associated with tissue culturing. In the present study, we applied CGH to identify chromosome anomalies in 60 spontaneous abortions of the first trimester, that had failed to grow in culture. In 57 out of 60 cases CGH analyses were successful. The overall aneuploidy rate detected was 72%. Trisomy was the predominant chromosome anomaly accounting for 68.0% of abnormal abortions, followed by triploidy (17.1%) and monosomy X (9.8%). An unbalanced structural rearrangement was found in one (2.4%) abortion. Most frequently involved in trisomies were chromosomes 16 (32.1%), 7 and 22 (10.7% each), 4, 13, 15, and 21 (7.2 % each). Three triploid cases and one complete mole were detected by microsatellite analysis as supplementary method. CGH data on culture failures were compared with data derived from 4693 successfully karyotyped first trimester spontaneous abortions, resulting in a chromosome aberration rate of 64.8%. The distribution of the different chromosome anomalies was similar with the exception of a higher rate of trisomies 7 and of XYY-triploidies in the culture failures. Based on our data we suggest that the genetic contribution to pregnancy loss is still underestimated. Investigating abortion tissues hitherto unassessed by conventional methods, we suggest that the contribution of chromosome aberrations to first trimester pregnancy loss is nearly 70%.

Is there a correlation between morphological and cytogenetic findings in placental tissue from early missed abortions

SummaryA retrospective study of 200 missed abortions was performed to determine whether morphological criteria alone are sufficient to ascertain a chromosomal aetiology. Placental changes were clasified into five morphological and four morphometric groups, according to the severity of alterations, and were then correlated with the cytogenetic data. The rate of chromosome anomalies was approximately 50% and was thus not significantly different within the groups II–V, but it was 80% in group I, which covered the most severe placental alterations, namely the partial hydatidiform moles. There was a high incidence of triploidies in group I, trisomies with obligatory early lethality in groups II and III, and X-monosomies in group III. Our findings do not support previous evidence regarding the specificity of certain villous alterations in association with chromosome aberrations. Indeed, they indicate that the placental villi may react similarly to chromosomal and nonchromosomal disturbances and that placental morphology depends on the severity and the temporal onset of the underlying disorder rather than on its type. With respect to chorionic villus samplings (CVS), this would mean that an abnormal villous structure may be suggestive for a chromosome anomaly but does not exclude a normal karyotype.

Roberts syndrome and SC phocomelia. A single genetic entity

A family with three siblings showing different manifestations of Roberts syndrome or SC phocomelia is described. With regard to previously published cases of familial Roberts syndrome and SC phocomelia we conclude that these two syndromes are one and the same genetic entity.

Descriptive neuropathology of chromosomal disorders in man

SummaryMorphological investigations were carried out on brains of 274 foetuses and children with a verified chromosomal anomaly. In more than two thirds of these cases pathological changes were not detectable. In the other cases the most frequent findings were: (1) holoprosencephaly/arhinencephaly, mainly observed in trisomy 13, but also in one case each of trisomy 18 and trisomy 21; (2) corpus callosum defects, mainly found in trisomy 18, but also in some cases of trisomies 13 and 21; (3) cerebellar nerve cell heterotopias and cerebral microdysplasias, present mainly in trisomy 21, but also in trisomies 13 and 18 as well as in cases with different chromosomal syndromes; (4) small hamartomas of the brain stem were found in two cases of trisomy 18.In a control group of 85 cases with “multiple malformations”, but without a verified chromosomal anomaly, similar observations were recorded. In particular, in a subgroup of cases with ascertained normal karyotype (31 out of 85 cases) seven holoprosencephalies, four corpus callosum defects, eight cerebellar heterotopias as well as three cerebral cortical microdysplasias and three stenoses of the aqueduct were found.It thus seems reasonable to assume that structural alterations of the central nervous system (CNS) are neither constant nor obligatorily accompanying a specific chromosomal syndrome. However, their appearance follows patterns of semi-specificity. On the other hand, one has to realize that in about one third of holoprosencephalies no chromosome anomaly is present. Moreover, cerebellar nerve cell heterotopias cannot be considered as “true” malformations, since they are very frequently found in normal newborns (mostly prematures), and disappear progressively with increasing age (“transitional microdysplasias”).

Low incidence of UPD in spontaneous abortions beyond the 5th gestational week.

Approximately 15–20% of all clinically recognised pregnancies abort, most commonly between 8–12 gestational weeks. While the majority of early pregnancy losses is attributed to cytogenetic abnormalities, the aetiology of approximately 40% of early abortions remains unclear. To determine additional factors causing spontaneous abortions we retrospectively searched for uniparental disomies (UPD) in 77 cytogenetically normal diploid spontaneous abortions. In all cases an unbalanced chromosome anomaly was ruled out by cytogenetic investigation of chorionic/amniotic membranes and/or chorionic villi. For UPD screening microsatellite analyses were performed on DNA of abortion specimens and parental blood using highly polymorphic markers showing UPD in two cases. The distribution of markers analysed indicated maternal heterodisomy for chromosome 9 (UPhD(9)mat) in case 1 and paternal isodisomy for chromosome 21 (UPiD(21)pat) in case 2. The originating mechanism suggested was monosomy complementation in UPiD(21)pat and trisomy rescue in UPhD(9)mat. In the case of UPhD(9)mat purulent chorioamnionitis was noted and a distinctly growth retarded embryo of 3 cm crown-rump length showing no gross external malformations. Histological analysis in the case of UPiD(21)pat suggested a primary anlage defect. Our results indicate that less than 3% of genetically unexplained pregnancy wastage is associated with total chromosome UPD. UPD may contribute to anlage defects of human conception. Chromosome aneuploidy correction can occur in very early cleavage stages. More research, however, ought to be performed into placental mosaicism to further clarify timing and mechanisms involved in foetal UPD.

Severe Facial Clefts in Acrofacial Dysostosis : A Consequence of Prenatal Exposure to Mycophenolate Mofetil?

BACKGROUND: Immunosuppressants are teratogenic in mice, rats, and rabbits and cause prenatal growth restriction in humans. As yet, there has been no proven teratogenicity in humans. CASE: We present a chromosomally normal fetus with severe acrofacial dysostosis and orofacial clefts. These were bilateral transverse and oblique clefts and defects of the midface. In addition, there were preaxial limb anomalies with digitalization of thumbs and internal cardiovascular, gastrointestinal, and urogenital malformations. The mother had been treated with high doses of the immunosuppressant mycophenolate mofetil in early pregnancy for systemic lupus erythematosus. CONCLUSION: Mycophenolate mofetil may have contributed to or even caused acrofacial dysostosis phenotype and extensive clefting.

Isochromosome 18q with karyotype 46,XX,i(18q). Cytogenetics and pathology

Cytogenetic and morphological findings of a 20‐gestational‐week‐old female fetus with karyotype 46, XX, i(18q) are reported. The fetus displayed clinical features resembling Edwards syndrome. No characteristic symptoms of monosomy 18p could be observed.

Raine syndrome: report of a family with three affected sibs and further delineation of the syndrome.

&NA; We describe three affected sibs with Raine syndrome born to a consanguineous Turkish couple. Clinical findings and post‐mortem assessment are presented. We have added previously unreported meso and severe telebrachyphalangy and urogenital anomalies to the clinical spectrum. Appositional new bone formation may be mistaken for fractures and callus formation ‐ both prenatally by ultrasound and postnatally in radiographs. Further research is required to detect the underlying metabolic and molecular defects of this autosomal recessive syndrome. Clin Dysmorphol 12:153‐160

A patient severely affected by spinal neurofibromas carries a recurrent splice site mutation in the NF1 gene.

Spinal neurofibromas are found in up to 38% of NF1 patients. However, they cause clinical implications only in about 5% of the patients. In contrast, multiple symptomatic spinal neurofibromas are the main clinical finding in patients with familial spinal neurofibromatosis. Familial spinal neurofibromatosis has been considered to be a distinct clinical form of neurofibromatosis. Linkage analysis in two families and identification of a NF1 gene mutation in a third family strongly associate spinal neurofibromatosis with the NF1 gene. We describe a NF1 patient who satisfies the NIH diagnostic criteria and has severe spinal involvement with bilateral spinal root neurofibromas at every level. A recurrent splice site mutation (IVS19b-3C>G) was identified in the NF1 gene in the patient. We discuss the possibility that the clinical picture of this patient represents an additional example of spinal neurofibromatosis. By comparison of the clinical expression of NF1 in this patient and that in another patient with the identical mutation the hypothesis that spinal neurofibromatosis is associated with a particular mutation is highly unlikely. The involvement of other genes linked to the NF1 gene or modifying genes is currently the most likely explanation for the clinical phenotype of spinal neurofibromatosis.

Trisomy 2q35-q37 due to insertion of 2q material into 17q25: clinical, cytogenetic, and molecular cytogenetic characterization.

We present a 7-year-old boy with growth retardation, developmental and mental delay, and minor physical abnormalities. The patient had a male karyotype with duplicated material of unknown origin in the long arm of chromosome 17. The origin of the duplicated material was clarified by fluorescence in situ hybridization. Forward chromosome painting showed that the extra material originated from chromosome 2, which was inserted into 17q25. Further characterization of the aberrant chromosome 17 by microdissection and reverse chromosome painting revealed a duplication of bands 2q35 to q37.1. To our knowledge, no other individual with a duplication of this small segment has been described so far. The clinical findings of 13 cases with isolated trisomy 2q are reviewed in relation to the size of the duplicated region. Functional analysis of the duplicated 2q region suggests that critical loci for visceral and central nervous system development in distal trisomy 2q are proximal to 2q33.