Detection of trisomy 18 on formalin-fixed and paraffin-embedded material by fluorescence in situ hybridization

Unrecognized viral infections and chromosome abnormalities as a cause of fetal death - examination with fluorescence in situ hybridization, immunohistochemistry and polymerase chain reaction

Fifteen to 50% of fetal deaths remain unexplained after post-mortem examination depending on inclusion criteria and classification systems. Our aim was to examine a selection of unexplained fetal deaths in order to investigate whether any common chromosome aberrations or viral infections were present. Reports from 351 fetal autopsies performed at the Department of Pathology and Medical Genetics at St. Olavs University Hospital from 2001 through 2010 were reviewed. Of these, 105 fetal deaths were classified as unexplained. Tissue samples from 30 cases were further examined with fluorescence in situ hybridization (FISH) to detect abnormalities in chromosomes 13, 18, and 21. The samples were also examined with immunohistochemistry (IHC) and polymerase chain reaction (PCR) to detect infections with cytomegalovirus, parvovirus B19, herpes simplex virus 1 and 2, enterovirus, and parechovirus. In two cases, a possible trisomy 13 mosaicism was found. No viruses were detected. In our selection of 30 unexplained cases, possible trisomy 13 mosaicism was found in two cases, and no viruses were detected. High degree of maceration and missing placental examination often complicate the investigation of fetal death, and extensive ancillary examinations do not necessarily contribute to a more specific diagnosis.

Trissomia 18: revisão dos aspectos clínicos, etiológicos, prognósticos e éticos

OBJETIVO: Revisar as características clínicas, etiológicas, diagnósticas e prognósticas da trissomia do cromossomo 18 (síndrome de Edwards). FONTES DE DADOS: Foram pesquisados artigos científicos presentes nos portais MedLine, Lilacs e SciELO, utilizando-se os descritores 'trisomy 18' e 'Edwards syndrome'. A pesquisa não se limitou a um período determinado e englobou artigos presentes nestes bancos de dados. SÍNTESE DOS DADOS: A síndrome de Edwards é uma doença caracterizada por um quadro clínico amplo e prognóstico bastante reservado. Há descrição na literatura de mais de 130 anomalias diferentes, as quais podem envolver praticamente todos os órgãos e sistemas. Seus achados são resultantes da presença de três cópias do cromossomo 18. A principal constituição cromossômica observada entre estes pacientes é a trissomia livre do cromossomo 18, que se associa ao fenômeno de não disjunção, especialmente na gametogênese materna. A maioria dos fetos com síndrome de Edwards acaba indo a óbito durante a vida embrionária e fetal. A mediana de sobrevida entre nascidos vivos tem usualmente variado entre 2,5 e 14,5 dias. CONCLUSÕES: O conhecimento do quadro clínico e do prognóstico dos pacientes com a síndrome de Edwards tem grande importância no que diz respeito aos cuidados neonatais e à decisão de instituir ou não tratamentos invasivos. A rapidez na confirmação do diagnóstico é importante para a tomada de decisões referentes às condutas médicas. Muitas vezes, as intervenções são realizadas em condições de emergência, sem muita oportunidade de reflexão ou discussão, e envolvem questões médicas e éticas difíceis.

Comparison between prenatal ultrasound and postmortem findings in fetuses and infants with developmental anomalies

OBJECTIVE

To determine if postmortem examinations of fetuses and infants change the diagnosis obtained at prenatal ultrasound and affect counseling of future pregnancies, and if there has been a change over recent years in the accuracy of prenatal ultrasound diagnosis.

METHODS

This was a retrospective review of 455 autopsies of fetuses and infants with developmental anomalies performed at Trondheim University Hospital between 1995 and 2004 and with a prenatal ultrasound examination performed at a tertiary referral center. The routine ultrasound examinations were performed by specially trained midwives and obstetricians, referral scans by fetal medicine experts and autopsies by consultant pathologists with experience in perinatal pathology. The results of this study were also compared with those of a previous similar study performed between 1985 and 1995, with fetuses and infants coming from the same population and diagnosed at the same center.

RESULTS

Of all cases analyzed during the study period, there was complete agreement between prenatal ultrasound and postmortem findings in 84% (384/455), i.e. prenatal ultrasound diagnoses were supplemented by postmortem examinations in 16% (71/455). Autopsy findings in four of these cases influenced further counseling. There was agreement regarding the main diagnosis in 98% (445/455) of cases. In the previous 10-year period, there was complete agreement in 75% and the main diagnosis was correct in 90% of cases. These differences between the two time periods were statistically significant (P = 0.0004 and P < 0.0001, respectively). The most frequent defects involved the central nervous system, heart and urinary tract. For these defects, detection rates for the main diagnoses were significantly better in 1995-2004 compared with in the previous 10-year period (P = 0.0125, P = 0.0111 and P = 0.0241, respectively).

CONCLUSION

The accuracy of prenatal sonographic detection of developmental anomalies has increased in recent years. However, postmortem examination is still necessary to verify or improve the prenatal diagnosis and may influence future counseling.

The use of comparative genomic hybridization and fluorescent in situ hybridization in postmortem pathology investigation of congenital malformations

Chromosomal abnormalities are an important cause of multiple congenital anomalies (MCA). However, conventional cytogenetic analysis using culture is unsuccessful in 10% to 40% of the cases. The purpose of this study was to examine if retrospective chromosomal analysis was possible on paraffin-embedded autopsy material with new techniques, including comparative genomic hybridization (CGH) and fluorescent in situ hybridization (FISH). We investigated 92 patients, including 71 patients with MCA, 17 patients with an isolated congenital anomaly, and 4 normal controls, by conventional CGH analysis and/or FISH. The karyotype was known in 52 cases, of which 26 patients were normal and 26 had chromosomal anomalies. Comparative genomic hybridization or FISH confirmed all but 2 cases, which were not interpretable. In 40 patients the karyotype was unknown but could be analyzed successfully in 36 cases (90%) by CGH. In this series, we found 1 additional chromosomal aberration, 45,X (Turner syndrome). Furthermore, we examined the postmortem material of 12 patients by FISH, confirming a known abnormal karyotype in 9 patients, an abnormal karyotype found by CGH in 1 case, and confirming DiGeorge syndrome (22q11 deletion) in twins. Comparative genomic hybridization and FISH are reliable techniques with which to perform retrospective genetic analysis on paraffin-embedded autopsy material.

Detection of genetic alterations by immunoFISH analysis of whole cells extracted from routine biopsy material

The detection of genetic abnormalities (eg, translocations, amplifications) in paraffin-embedded samples by the fluorescence in situ hybridization (FISH) technique is usually performed on tissue sections. FISH analysis of nuclei extracted from paraffin-embedded samples is also possible, but the technique is not widely used, principally because of the extra labor involved and the loss of information on tissue architecture. In this article, we report that nuclei extracted from paraffin-embedded tissue often retain at least part of the surrounding cytoplasm. Consequently, immunocytochemical labeling for a range of cellular markers (eg, of lineage or proliferation) can be performed in combination with FISH labeling, allowing specific cell populations to be analyzed for genetic abnormalities. These cell preparations are largely free of the problems associated with tissue sections (eg, truncation artifact, signals in different focal planes) so that interpretation is easy and numerical chromosomal abnormalities are readily assessed. Cells isolated from paraffin sections can be stored in suspension so that arrays can be created as and when needed from a range of neoplasms for investigation by the immunoFISH technique (for example, for studying a new genetic abnormality). This procedure represents a novel methodology, which in some settings offers clear advantages over analysis of tissue sections.

My approach to performing a perinatal or neonatal autopsy

An opportunity to determine the cause of death, factors that may have a role in it, and the extent and cause of malformations is provided by perinatal autopsy. The family may be assisted in finding closure after the death of their infant by the information obtained. Insight into classifying infants appearing normal into one of three groups, small, appropriate and large for gestational age, has been provided, as each group tends to have specific causes of death. In infants with congenital anomalies, patterns of malformation may lead us to the diagnosis. An accurate diagnosis is required to provide counselling for a subsequent pregnancy.