Prenatal diagnosis of the Pallister-Killian mosaic aneuploidy syndrome by CVS

Structural brain abnormalities in Pallister-Killian syndrome: a neuroimaging study of 31 children

BACKGROUND

Pallister-Killian syndrome (PKS) is a rare genetic disorder caused by mosaic tetrasomy of 12p with wide neurological involvement. Intellectual disability, developmental delay, behavioral problems, epilepsy, sleep disturbances, and brain malformations have been described in most individuals, with a broad phenotypic spectrum. This observational study, conducted through brain MRI scan analysis on a cohort of patients with genetically confirmed PKS, aims to systematically investigate the neuroradiological features of this syndrome and identify the possible existence of a typical pattern. Moreover, a literature review differentiating the different types of neuroimaging data was conducted for comparison with our population.

RESULTS

Thirty-one individuals were enrolled (17 females/14 males; age range 0.1-17.5 years old at first MRI). An experienced pediatric neuroradiologist reviewed brain MRIs, blindly to clinical data. Brain abnormalities were observed in all but one individual (compared to the 34% frequency found in the literature review). Corpus callosum abnormalities were found in 20/30 (67%) patients: 6 had callosal hypoplasia; 8 had global hypoplasia with hypoplastic splenium; 4 had only hypoplastic splenium; and 2 had a thin corpus callosum. Cerebral hypoplasia/atrophy was found in 23/31 (74%) and ventriculomegaly in 20/31 (65%). Other frequent features were the enlargement of the cisterna magna in 15/30 (50%) and polymicrogyria in 14/29 (48%). Conversely, the frequency of the latter was found to be 4% from the literature review. Notably, in our population, polymicrogyria was in the perisylvian area in all 14 cases, and it was bilateral in 10/14.

CONCLUSIONS

Brain abnormalities are very common in PKS and occur much more frequently than previously reported. Bilateral perisylvian polymicrogyria was a main aspect of our population. Our findings provide an additional tool for early diagnosis.Further studies to investigate the possible correlations with both genotype and phenotype may help to define the etiopathogenesis of the neurologic phenotype of this syndrome.

Prenatal profile of Pallister-Killian syndrome: Retrospective analysis of 114 pregnancies, literature review and approach to prenatal diagnosis

Pallister-Killian syndrome (PKS) is a tissue limited mosaic disorder, characterized by variable degrees of neurodevelopmental delay and intellectual disability, typical craniofacial findings, skin pigmentation anomalies and multiple congenital malformations. The wide phenotypic spectrum of PKS in conjunction with the mosaic distribution of the i(12p) makes PKS an underdiagnosed disorder. Recognition of prenatal findings that should raise a suspicion of PKS is complicated by the fragmentation of data currently available in the literature and challenges in diagnosing a mosaic diagnosis on prenatal testing. Ultrasound anomalies, especially congenital diaphragmatic hernia, congenital heart defects, and rhizomelic limb shortening, have been related to PKS, but they are singularly not specific and are not present in all affected fetuses. We have combined prenatal data from 86 previously published reports and from our cohort of 114 PKS probands (retrospectively reviewed). Summarizing this data we have defined a prenatal growth profile and identified markers of perinatal outcome which collectively provide guidelines for early recognition of the distinctive prenatal profile and consideration of a diagnosis of PKS as well as for management and genetic counseling.

Etiologies of uterine malformations

Ranging from aplastic uterus (including Mayer-Rokitansky-Kuster-Hauser syndrome) to incomplete septate uterus, uterine malformations as a group are relatively frequent in the general population. Specific causes remain largely unknown. Although most occurrences ostensibly seem sporadic, familial recurrences have been observed, which strongly implicate genetic factors. Through the study of animal models, human syndromes, and structural chromosomal variation, several candidate genes have been proposed and subsequently tested with targeted methods in series of individuals with isolated, non-isolated, or syndromic uterine malformations. To date, a few genes have garnered strong evidence of causality, mainly in syndromic presentations (HNF1B, WNT4, WNT7A, HOXA13). Sequencing of candidate genes in series of individuals with isolated uterine abnormalities has been able to suggest an association for several genes, but confirmation of a strong causative effect is still lacking for the majority of them. We review the current state of knowledge about the developmental origins of uterine malformations, with a focus on the genetic variants that have been implicated or associated with these conditions in humans, and we discuss potential reasons for the high rate of negative results. The evidence for various environmental and epigenetic factors is also reviewed. © 2016 Wiley Periodicals, Inc.

Rare case of Killian-Pallister syndrome associated with idiopathic short stature detected with fluorescent in situ hybridization on buccal smear

Background

Killian-Pallister syndrome (KPS) is a rare form of chromosomal mosaicism and is defined by the existence of an extra chromosome 12 in some cell lines in one individual. The degree of mosaicism varies among tissues and dictates the clinical presentation of the syndrome. The clinical features of Killian-Pallister syndrome include mental retardation, typical facial dysmorphism and pigmentation defects.

Case presentation

We present a rare case of Killian-Pallister syndrome with severe form of the disease associated with isolated growth hormone deficiency and low-rate mosaicism on buccal smear. The absence of a marker chromosome 12p in lymphocyte cultures and the low degree of mosaicism lead to frequent misdiagnosis of this condition.

Conclusions

The selection of tissue sampling is crucial in establishing the diagnosis of Killian-Pallister syndrome. Fluorescent in situ hybridisation on buccal smear remains the golden standard as a screening method if a suspicion of the syndrome exists.

Tetrasomy 12p (Pallister-Killian syndrome): difficulties in prenatal diagnosis

PURPOSE

We report a rare case of Pallister-Killian syndrome diagnosed prenatally with increased nuchal translucency during screening for trisomy 21.

MATERIALS AND METHODS

Echografic and postmortem examination of the fetus, G-banded chromosome and FISH analysis on short- and long-term chorion villous sampling (CVS) culture.

RESULTS AND DISCUSSION

Cytogenetic analysis revealed a supernumerary isochromosome 12p after long-term culture whereas a normal cell line was detected in short-term culture only. Sonografic examination in 17-weeks' gestation showed further increase of the NT and the additional presence of brachymelia, diaphragmatic hernia and a marked dextroposition of the heart. Termination of the pregnancy was performed. The cases of PKS karyotypically confirmed on CVS are reviewed, and cytogenetic and sonographic aspects of the prenatal diagnosis of PKS are discussed.

Pallister-Killian syndrome: a report of 2 cases and review of its surgical aspects

Pallister-Killian syndrome (PKS) is a rare mosaic genetic disorder defined by the presence of isochromosome for the short arm of chromosome 12. The authors report 2 new cases of PKS with prenatal diagnosis of tetrasomy 12p made by cytogenetic study of amniocytes. Typical dysmorphic craniofacial features were noted postnatally. Both newborns were referred to a surgical department because of congenital anomalies requiring operative management. One had an imperforate anus with an anocutaneous fistula and underwent minor anorectoplasty on day 2 of life. The second newborn required emergency laparotomy because of malrotation with midgut volvulus. This is the first report of clinical manifestation of malrotation in a patient with PKS. The authors undertook a detailed review of reported to date cases of PKS with special emphasis on its surgical aspects.

Isochromosome 5p mosaicism at prenatal diagnosis: observations and outcomes in six cases at chorionic villus sampling and one at amniocentesis

We present six cases of 47,+i(5p)/46 mosaicism diagnosed at chorionic villus sampling (CVS), this being the first prospective series to be reported. The clinical indication in each was advanced maternal age. Further prenatal studies in four (amniocentesis, plus fetal blood sampling in one) did not show the isochromosome. In one case, subsequent amniocentesis showed 1/48 in situ colonies with the isochromosome, but fetal blood was karyotypically normal. These five pregnancies resulted in phenotypically normal livebirths; further normal follow-up reports (from age 4 months through 4 years) are noted in four of these. Analysis of placental tissue in one case confirmed the presence of the i(5p) mosaicism. In the remaining case, in which 100% of CVS cultured cells had the i(5p), the pregnancy was terminated. Fetal skin fibroblasts did not show the i(5p). Thus, in none of these six cases was true fetal mosaicism detected, nor an abnormal phenotype noted. We suggest that a 47,+i(5p)/46 karyotype, detected at CVS, may frequently reflect confined placental mosaicism. In addition, we report a case of the primary diagnosis of 47,+i(5p)/46 mosaicism at amniocentesis. The infant appeared normal at birth, but a brain malformation was subsequently identified.

Tissue-limited mosaicism in Pallister-Killian syndrome -- a case in point

We report a case of Pallister-Killian syndrome in a term female infant. Antenatal ultrasound showed left diaphragmatic hernia and polyhydramnios. She was ventilated from birth and the diaphragm defect repaired on day 5. She had dysmorphic features, including median cleft palate, patchy frontotemporal alopecia, hypopigmented skin whorls, and bilateral profound sensorineural hearing loss. Fetal and postnatal karyotypes of peripheral lymphocytes were both normal, 46, XX. Subsequently, a skin fibroblast culture showed mosaic tetrasomy of isochromosome 12p both on G-banding and fluorescence in situ hybridization, consistent with Pallister-Killian syndrome. This case illustrates the importance of using the appropriate sample type for karyotype analysis with implications for prenatal and postnatal diagnosis.

Pallister-Killian syndrome: difficulties of prenatal diagnosis

The first prenatal diagnosis of Pallister-Killian syndrome (PKS) was reported by Gilgenkrantz et al. in1985. Since this report, about 60 prenatal cases have been reported but both sonographic and cytogenetic diagnoses remain difficult. Although ultrasound anomalies such as congenital diaphragmatic hernia, polyhydramnios and rhizomelic micromelia in association with fetal overgrowth are very suggestive of the syndrome, they are inconstant and they may even be absent. The mosaic distribution of the supernumerary isochromosome 12p greatly increases these difficulties. No prenatal cytogenetic technique is sensitive enough to ensure prenatal diagnosis and false-negative results have been described on fetal blood, chorionic villi and amniocentesis. We report here two prenatal cases of PKS which illustrate the great variability of the fetal phenotype. In reviewing the 63 reported cases, we attempt to determine ultrasound indicators of the syndrome and to define a cytogenetic strategy. In cases where ultrasound indicators are present, our proposal is first to perform chorionic villus or placental sampling and then amniocentesis when the first cytogenetic result is normal. Fetal blood sampling is the least indicated method because of the low frequency of the isochromosome in lymphocytes. In this cytogenetic strategy, fluorescent in situ hybridization (FISH) and especially interphase FISH on non-cultured cells increases the probability or identifying the isochromosome. A misdiagnosis remains possible when ultrasound is not contributory; the identification of new discriminating ultrasound indicators would be very helpful in this context.

Report of two new cases of Pallister-Killian syndrome confirmed by FISH: tissue-specific mosaicism and loss of i(12p) by in vitro selection

Tissue-specific mosaic distribution of an additional isochromosome 12p is the characteristic chromosomal aberration in Pallister-Killian syndrome. Often it is confined to fibroblasts, whereas lymphocytes show a normal karyotype. Two cases are reported in which the distribution of the additional i(12p) was analysed in various tissues. The isochromosomes were characterised by conventional banding technics and fluorescence in situ hybridization (FISH). In the first case, diagnosed prenatally, 4 different tissues were analysed. A direct preparation of chorionic villi (21 gestational weeks) showed an extra marker chromosome in 19% and two additional copies in 3% of the examined cells. In two cultures of amniocytes (17 and 21 weeks), the i(12p) was observed in 23% and 12%, respectively. It was absent in cultured lymphocytes of fetal blood (21 weeks). The fibroblast long-term culture of umbilical cord showed the i(12p) in 100% of metaphases. In the second case of a term infant the i(12p) was diagnosed in cultured lymphocytes (4%) and fibroblasts (93%). Secondary loss of the isochromosome was evaluated by in vitro selection in case 2 analysing metaphases and interphases of fibroblasts in the 1st, 4th and 5th subculture using FISH. The proportion of cells with i(12p) decreased from 93% to 40% and to 28%, respectively. DNA analysis in case 1 showed a maternal meiotic origin of the i(12p). The prenatally detected clinical findings in both cases showed characteristic abnormalities of the Pallister-Killian syndrome.

The use of interphase FISH for prenatal diagnosis of Pallister-Killian syndrome

Pallister-Killian syndrome (tetrasomy 12p) is a relatively rare aneuploidy syndrome characterized by the presence of mosaicism for an isochromosome 12p [i(12p)]. We report two new cases diagnosed following chorionic villus sampling and an abnormal ultrasound, respectively. Fluorescent in situ hybridization (FISH) was used to enumerate the number of interphase cells containing the isochromosome. The results of these studies illustrate the importance of the use of interphase FISH to detect the presence of the i(12p) in uncultured, non-dividing cells. A review of the literature identified 23 additional cases of Pallister-Killian syndrome diagnosed prenatally. Approximately 50 per cent of these cases were associated with the presence of a congenital diaphragmatic hernia. We suggest that a perinatal-lethal form of Pallister-Killian syndrome is underdiagnosed and recommend that all cases of prenatally detected diaphragmatic hernia be tested for Pallister-Killian syndrome using interphase FISH on uncultured amniocytes.

Clinical variability of tetrasomy 12p

We describe five patients with tetrasomy 12p (one previously reported). These patients exhibit a very wide range of phenotypic features from that of classic Pallister-Killian syndrome to only mild learning disabilities with pigmentary skin changes. As such, these cases highlight the fact that tetrasomy 12p [i(12p)] and Pallister-Killian syndrome are not synonymous, although this combination of genotype and phenotype is often seen. This information is especially important in prenatally ascertained i(12p). The full spectrum of phenotypic possibilities associated with this chromosome aneuploidy should be discussed in prenatal counseling.

Pallister-Killian syndrome: a mild case diagnosed by fluorescence in situ hybridization. Review of the literature and expansion of the phenotype

Pallister-Killian syndrome (PKS) is a rare disorder characterized by a specific combination of anomalies, mental retardation and mosaic presence of a supernumerary isochromosome 12p which is tissue-limited. We report an atypical case of PKS with a mild phenotype. Flourescence in situ hybridization (FISH) was used to demonstrate that the supernumerary marker chromosome identified in the patient's fibroblasts was an isochromosome 12p. This study broadens the spectrum of PKS phenotype. It also illustrates the usefulness of fluorescence in situ hybridization in diagnosis of patients with chromosomal abnormalities and mild or atypical clinical findings.

Molecular cytogenetics: an essential component of modern prenatal diagnosis

Traditional cytogenetic studies with high-resolution banding techniques have been the mainstay of prenatal diagnosis for > 20 years. However, this approach is limited by the resolution of light microscopy, and it requires cultured cells, necessitating a significant delay in obtaining chromosome studies. The advent of molecular cytogenetics, or fluorescence in situ hybridization, has added an adjunctive tool to overcome both these limitations. During a 16-month period 35 prenatal diagnosis cases had molecular cytogenetic studies performed; 71% of the evaluations were informative. We present five of these cases to illustrate the benefits of this technique for clinical prenatal diagnosis.

Prenatal diagnosis of mosaic tetrasomy 12p/trisomy 12p by fluorescent in situ hybridization in amniotic fluid cells: a case report of Pallister-Killian syndrome

A prenatally detected case of a rare mosaic tetrasomy 12p/trisomy 12p is reported, presenting as the well-known accessory isochromosome 12p and a supernumerary single 12p marker in 17/24 and 6/24 clones of cultured amniotic fluid cells, respectively. The chromosomal nature of both marker chromosomes was investigated in cultured amniotic fluid cells by fluorescent in situ hybridization with various probes: the 12-centromeric probes p alpha 12H8 and D12Z3, a whole chromosome 12 paint, and the chromosome 12p-specific paint M28. DNA analysis revealed a maternal origin of the extra 12p material. After counselling, the parents requested termination of pregnancy. Inspection and autopsy of the fetus revealed many of the dysmorphisms and internal structural abnormalities of the Pallister-Killian syndrome.

Lethal Pallister-Killian syndrome: phenotypic similarity with Fryns syndrome

The Pallister-Killian syndrome is a sporadic multiple congenital anomaly syndrome characterized by "coarse" face, profound mental retardation, and epilepsy. Chromosomes of peripheral lymphocytes are usually normal, but tissue cultures show varying degrees of mosaicism for isochromosome 12p. In babies who die neonatally of severe malformations, including diaphragmatic hernia, and who also have a "coarse" face, acral hypoplasia, and other internal anomalies, Fryns syndrome is more likely to be suspected than Pallister-Killian syndrome, especially if karyotyping is unavailable or if peripheral lymphocytes have a normal chromosome constitution. An initial diagnosis of Fryns syndrome had to be modified in 3 successive newborn infants since chromosome analysis or in situ hybridization with a chromosome 12 probe on kidney tissue demonstrated the mosaic aneuploidy characteristic of Pallister-Killian syndrome. These 3 patients confirm that a similar pattern of malformations can be present in both conditions at birth. It consists of "coarse" face, acral hypoplasia, diaphragmatic hernia, and other defects. Newborn infants who present this phenotype, but lack a conclusively normal chromosome test, may not have Fryns syndrome. A diagnosis of Fryns syndrome should be made carefully to avoid the risk of inappropriate genetic counseling.

Prenatal diagnosis and clinical findings in a case of hexasomy 12p

We report the first case of hexasomy 12p mosaicism due to 2 copies of an apparent i(12p) [46,XX/48,XX, +i(12p), +i(12p)]. In every cell that contained the i(12p), 2 copies of the marker were found. The hexasomy was found in amniocytes (16%) and skin fibroblasts (95%) but not in peripheral blood lymphocytes. The chromosomal origin of the marker was confirmed with the use of in situ hybridization of alpha-satellite specific for the centromere of chromosome 12. The present case was diagnosed following chromosome analysis for anomalies on ultrasound. The hexasomy 12p patient showed striking phenotypic similarities with severely affected tetrasomy 12p cases and died shortly after birth. We propose that the more severe presentation of this case is due to the 4 extra copies of 12p.

Pallister-Killian and Fryns syndromes: nosology

Fryns syndrome is a lethal autosomal recessive multiple congenital anomaly syndrome characteristic "coarse" facies, cleft palate, diaphragmatic hernia, and distal digital hypoplasia. The appearance of the face and digits is very similar to that observed in Pallister-Killian syndrome (mosaic isochromosome 12p), although the incidence of cleft palate, diaphragmatic hernia, and neonatal death is much lower in the latter condition. We report on an infant with many manifestations of Fryns syndrome ("coarse" face, cleft palate, cloudy corneae, diaphragmatic hernia, distal digital hypoplasia, and neonatal death) who was found to be mosaic for i(12p). Her diagnosis was changed to Pallister-Killian syndrome and the family was counselled accordingly. The clinical overlap between Fryns and Pallister-Killian syndromes is discussed. Because the chromosome abnormality in Pallister-Killian syndrome is often limited to fibroblasts and may be selectively eliminated both in vivo and in vitro, some Pallister-Killian patients may be misdiagnosed with Fryns syndrome and given an erroneously high recurrence risk. Newborn infants with the Fryns or Pallister-Killian phenotypes should have chromosome studies involving multiple tissues so that the correct diagnosis can be made. This will contribute to the understanding of both disorders and facilitate appropriate genetic counselling.

New diagnostic method for Pallister-Killian syndrome: detection of i(12p) in interphase nuclei of buccal mucosa by fluorescence in situ hybridization

Detection of the supernumerary isochromosome 12p [i(12p)] was performed on buccal smear preparations from 2 patients with Pallister-Killian syndrome, 21 (patient 1) and 15 months (patient 2) old, by interphase fluorescence in situ hybridization (FISH) using a chromosome 12-specific alpha satellite probe. Isochromosome 12p-positive cells were identified by observing 3 signals over the nucleus, while diploid cells had 2 signals. The proportion of i(12p)-positive cells thus identified was high in the epithelial cells of buccal mucosa at 68 and 53% from patients 1 and 2, respectively. Further, the frequencies of i(12p)-positive cells were also studied in PHA-stimulated peripheral lymphocytes, cultured skin fibroblasts (both patients), and directly harvested T and B-cells (patient 1). Of these tissues, buccal mucosa showed the highest proportion of i(12p)-positive cells. These findings indicate that epithelial cells of buccal mucosa are likely to retain i(12p)-positive cells. Detection of i(12p) using direct buccal smear preparations by interphase FISH is a rapid, effective and non-invasive method for confirming the diagnosis of the Pallister-Killian syndrome.