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epd.2013.0618 Auteur(s) : Shailendra Kapoor shailendrakapoor@yahoo 23111 Mechanicsville Virginia, USA To the Editor, I read with great interest the recent article by de Palma et al. (2012), entitled “Eating-induced epileptic spasms in a boy with MECP2 duplication syndrome: insights into pathogenesis of genetic epilepsies”. A common cause of “epileptic spasms” that is often overlooked and under recognised is Pallister-Killian syndrome (PKS). PKS or “Pallister mosaic aneuploidy syndrome” [...]

Pallister-Killian syndrome (tetrasomy 12p) is an uncommon aneuploidy, which may present in the prenatal period with an ultrasonographically detected fetal abnormality or following karyotyping for maternal age. We report a case that presented with increased nuchal translucency and hydrops at a first trimester screening scan for trisomy 21.

Pallister-Killian syndrome is a rare syndrome of multiple congenital anomalies attributable to the presence of a mosaic supernumerary isochromosome (12p). Although the clinical manifestations of Pallister-Killian syndrome are variable, the most common anomalies include craniofacial dysmorphisms, limb deformities, progressive psychomotor development delay, severe hypotonia, and epilepsy. Standard karyotype is nearly always normal, but the isochromosome (12p) is present in a high percentage of skin fibroblasts. In this article, we report the case of 2 boys with Pallister-Killian syndrome having late-onset, drug-resistant epileptic spasms. Seizures have been reported in 40% of patients with Pallister-Killian syndrome but are poorly described. Epileptic spasms are not unusual in patients with brain malformations, chromosomal aberrations, and genetic syndromes, but epileptic spasms could be easily mistaken for behavioral manifestations. A better electroclinical characterization of epileptic seizures in Pallister-Killian syndrome using appropriate polygraphic tests (video-electroencephalography, electromyography) may lead to an early diagnosis and specific treatment for this form of epileptic spasms caused by this rare syndrome.

Udgivelsesdato: 2009-Feb-1 We report on a 5-year-old girl with Pallister-Killian syndrome (OMIM #601803) due to mosaicism of two supernumerary isochromosomes (hexasomy 12p). Hexasomy 12p was found in 20% of the cells by chromosome analysis of cultured skin fibroblasts and confirmed by FISH- and arrayCGH analysis. The girl has woolly and sparse hair, absence of lateral eyebrows, dry skin, brittle nails, hypopigmented patches, frontal bossing, hearing loss, hypertrophic dilated cardiomyopathy, polydactyly, and mild developmental delay. This is the second live case of mosaicism for hexasomy 12p to be reported. A gene-dosage hypothesis has previously suggested that cases with hexasomy 12p would have a worse phenotype than cases with tetrasomy 12p. The relatively mild symptoms found in the current girl with hexasomy 12p may to contradict this hypothesis.

A new case of mosaic tetrasomy 12 p (46, XY/47, XY, + i 12 p), diagnosed during pregnancy from ultrasonographic signs, is reported. We emphasize the peculiar position of the diaphragmatic hernia in this syndrome. Its presence or absence determines the vital prognosis and the age of diagnosis. The knowledge of its possible association with tetrasomy 12 p can contribute considerably to the neonatal diagnosis by directing the work of the cytogeneticist to tissue cultures which enable him to detect the presence of the tetrasomy.

Pallister-Killian syndrome (PKS; OMIM: # 601803) is a rare sporadic syndrome of multiple congenital anomalies attributable to the presence of a de novo mosaic supernumerary isochromosome 12p [i(12p)]. The syndrome presents with a recognizable pattern of findings including: pigmentary skin changes, characteristic facial features (sparse anterior scalp hair, flattened midface, macrostomia, and coarsening of the facial features), and developmental delay. The developmental phenotype of PKS is quite variable, but most are considered to fall into the profound range of developmental retardation. We report on two individuals with classical features of PKS. Notably, in one child the neuropsychological development was significantly more favourable than commonly reported in the literature. This illustrates the loose correlation between geno- and phenotype in PKS.

The Pallister-Killian Syndrome (PKS; OMIM #601803), also known as Tetrasomy 12p or Mosaic Isochromosome 12p syndrome, is a rare genetic dis-order in humans. Its exact incidence is not known. The PKS is due to a partial tetrasomy of the whole, or parts of, the short arm of chromosome 12. It was first described by Philip Pallister in 1977 and further studied by Maria Teschler-Nicola and W. Killian in 1981. Prenatally, PKS can be suggested due to relatively unspecific abnormal sonographic findings such as enhanced nuchal transluciency or abnormal hands or feet, as well as omphalocele. In a newborn or small child, PKS can be diagnosed with facial anomalies, streaks of hypo- or hyper-pigmentation, seizures and profound mental retardation. Charac-teristic for PKS is a tissue-limited mosaicism

A patient whose dysmorphism at birth was not diagnostic for Pallister–Killian syndrome (PKS) was found to have mosaic tetrasomy 12p by an array-based comparative genomic hybridization of peripheral blood DNA. He was determined to be mosaic for 46,XY,trp(12)(p11.2 p13) in cultured skin fibroblasts. His appearance was typical for PKS at 4 months of age. © 2007 Wiley-Liss, Inc.

Somatic chromosomal mosaicism is a well-established cause for birth defects, mental retardation, and, in some instances, specific genetic syndromes. We have developed a clinically validated, targeted BAC clone array as a platform for comparative genomic hybridization (aCGH) to enable detection of a wide range of pathologic copy number changes in DNA. It is designed to provide high sensitivity to detect well-characterized submicroscopic micro-deletion and duplication disorders while at the same time minimizing detection of variation of uncertain clinical significance. In the course of studying 2,585 samples submitted to our clinical laboratory, chromosomal mosaicism was detected in 12 patient samples; 10 of these cases were reported to have had a normal blood chromosome analysis. This enhanced ability of aCGH to detect mosaicism missed by routine chromosome analysis may be due to some combination of testing multiple cell lineages and/or failure of cytogenetically abnormal T lymphocytes to respond to mitogens. This suggests that aCGH may detect somatic chromosomal mosaicism that would be missed by conventional cytogenetics.

We report the case of a 19-month-old boy with Pallister–Killian syndrome associated with West syndrome. The child was born at term to a healthy mother after an uneventful pregnancy. He was born by cesarean section because of fetal macrosomia. He was observed to have nystagmus, craniofacial dysmorphism, and mental retardation. Intractable epileptic spasms developed 17 months after birth, and electroencephalography revealed a modified hypsarrhythmia. The seizures were uncontrollable with sodium valproate monotherapy. At the age of 19 months, the child was diagnosed with Pallister–Killian syndrome of mosaic tetrasomy 12p by fluorescence in situ hybridization. Combination treatment with high-dose pyridoxal phosphate and sodium valproate eliminated seizures and improved the electroencephalographic abnormalities. To our knowledge, this is the first reported case of Pallister–Killian syndrome associated with West syndrome.

The advent of microarray-based comparative genomic hybridization (array CGH) promises to revolutionize clinical cytogenetics because of its ability to rapidly screen the genome at an unprecedented resolution. Yet, the ability of array CGH to detect and evaluate low-level mosaicism is not known. Our laboratory has analyzed over 3,600 clinical cases with the SignatureChip which we developed for the detection of microdeletions, microduplications, aneuploidy, unbalanced translocations, and subtelomeric and pericentromeric copy number alterations. Here, we report 18 cases of mosaicism detected by array CGH in a routine diagnostic setting, 14 of which were not known to us at the time of the analysis. These 14 cases represent approximately 8% of all abnormal cases identified in our laboratory. For each case, fluorescence in situ hybridization (FISH) analysis was performed on PHA-stimulated cultures after mosaic chromosome abnormalities were suspected by array CGH. In all cases, FISH confirmed the mosaic chromosome abnormalities which included a variety of marker chromosomes, autosomal trisomies, terminal and interstitial deletions, and derivative chromosomes. Interestingly, confirmatory FISH analyses on direct blood smears indicated that the percentage of abnormal cells in unstimulated cultures was in some cases different than that found in PHA-stimulated cells. We also report the detection of a previously unsuspected case of an isochromosome 12p (associated with Pallister-Killian syndrome) by array CGH using genomic DNA extracted from peripheral blood. These results support a growing body of data that suggests that stimulated peripheral blood cultures likely distort the percentage of abnormal cells and may, for some chromosome abnormalities, make their detection unlikely by conventional analysis. Thus, array CGH, which is based on genomic DNA extracted directly from uncultured peripheral blood, may be more likely to detect low-level mosaicism for unbalanced chromosome abnormalities than traditional cytogenetic techniques.

allister-Killian syndrome (PKS, also referred as tetrasomy 12p) is a rare sporadic chromosomic anomaly characterized by the presence, most often in a mosaic arrangement, of isochromosome 12p.1–3 Patients have 4 copies of the short arm of chromosome 12 instead of the normal 2. Prenatal diagnosis is made by showing the presence of the supernumerary isochromosome by fluorescence in situ hybridization in amniotic fluid, a chorionic villus sample, or fetal lymphocytes.3,4 Such a chromosomic defect is most often associated with multiple morphologic anomalies, such as a diaphragmatic hernia, rhizomelic shortening of the limbs, cardiac and urogenital defects, joint contractures, and facial dysmorphic features.1,4 However, these anomalies may not be fully expressed during the first half of pregnancy, which makes early prenatal diagnosis by sonography difficult. Neurodevelopmental delays, seizures, and abnormal skin pigmentation are common in postnatal survivors with PKS.5 To date, about 60 cases of prenatally diagnosed PKS have been published.4 Either the diagnosis has been made after the sonographic detection of fetal anomalies,2 or it has been an unexpected finding after fetal karyotyping for maternal age.4 Recently, an association of PKS with increased nuchal translucency (NT) in the first trimester of pregnancy has been reported.1 The effectiveness of this sonographic marker for detection of both chromosomic defects and anatomic anomalies is now well established, and its use as a screening tool in the first trimester of gestation has become widespread.6,7 Likewise, in recent years, the ability of early echocardiography to detect fetal congenital heart disease early in high-risk pregnancies has been proved.8 Here, we report a case of early prenatal diagnosis of PKS made by showing both increased NT and a complex congenital cardiac defect in the setting of a screening program for common aneuploidies in the first trimester. Received April 10, 2006, from the Ultrasound and Fetal Physiopathology Unit, Department of Obstetrics and Gynecology (D.E.A., J.A.G., A.G.I.), and Human Genetics Unit (A.M.I.), Hospital Universitario 12 de Octubre, Madrid, Spain; and Department of Human Anatomy and Embryology, Faculty of Medicine, University of Extremadura, Badajoz, Spain (C.L.-S., V.G.-M.). Revision requested May 1, 2006. Revised manuscript accepted for publication May 25, 2006. This work was supported in part by grant 3PR05A058 from the Plan Regional de Investigacion, Consejeria de Educacion, Ciencia y Tecnologia, Junta de Extremadura. Address correspondence to Alberto Galindo Izquierdo, MD, Servicio de Obstetricia y Ginecologia, Hospital Universitario 12 de Octubre, Avenida de Cordoba s/n, 28041 Madrid, Spain. E-mail: agalindo.hdoc@salud.madrid.org Abbreviations NT, nuchal translucency; PKS, Pallister-Killian syndrome

Pallister-Killian syndrome (PKS) is a rare syndrome of multiple congenital anomalies attributable to the presence of a mosaic supernumerary isochromosome 12p. The syndrome presents with a recognizable pattern of findings including: pigmentary skin changes, characteristic facial features (sparse anterior scalp hair, flattened midface, macrostomia, and coarsening of the facial features), and developmental delay. The developmental phenotype of PKS is quite variable, but most are considered to fall into the profound range of developmental retardation. We report on an individual with classical features of PKS with development significantly better than that reported in the literature. Developmental and behavioral testing in this individual alters the range of developmental expectation in PKS, and highlights the need for consideration of chromosomal analysis in individuals with normal or near-normal intelligence if other physical phenotypic features of PKS are present.

Pallister-Killian syndrome (PKS) is a rare, sporadic, genetic disorder characterized by dysmorphic features, learning disability*, and epilepsy. It is caused by a mosaic supernumerary isochromosome 12p (i[12p]). The i(12p) is rarely found in peripheral blood but it is present in skin fibroblasts. Recognition is essential for cytogenetic diagnosis. We describe a male aged 2 years 6 months and a female aged 11 years with PKS and epileptic spasms (ES). This type of seizure is not unusual in patients with brain malformations and with severe developmental delay, but it is sometimes difficult to recognize without video-electroencephalogram studies and could be mistaken for other types of seizure or behavioural manifestations. In these two patients with PKS, spasms had late onset, persisted beyond infancy, and were drug resistant. Clinicians should be aware of this possibility in PKS, which appears to be a rare cause of ES.

A dysmorphic patient was shown to carry a small supernumerary marker chromosome. Multicolor, centromere-multicolor and regular FISH experiments proved the marker to be an analphoid 12pter derived isochromosome. Microdissection of the marker followed by reverse painting and array CGH analysis showed that the isochromosome contains approximately 6 Mb of 12pter-12p13.31 derived sequence. This is only the second report of a marker with a neocentromere 12pter and the molecular fine mapping of the duplicated region further refines the 12p region defining the Pallister-Killian syndrome phenotype. In addition, we show the feasibility of using microdissected chromosomes or chromosomal fragments to molecularly map the chromosomal breakpoints on array CGH. This technology may aid in the identification of chromosomal translocation breakpoints.

Objective Advance knowledge about the mechanism of isochromosome formation. Methods Echographic examination of the foetus. G- and/or T-banded chromosome and FISH analysis using chromosome 12p subtelomeric probes on short- and long-term CVS cultures, amniocytes and foetal fibroblasts. Polymorphic CA repeat analysis on DNA from the foetus and both parents. Results Short-term CVS cultures showed a 46,XX karyotype, whilst long-term CVS cultures showed a 47,XX,+12 karyotype. FISH on amniocytes indicated 2, 3 and 4 signals. Foetal fibroblasts showed both 47,XX,+12 and 47,XX,+i(12)(p10) karyotypes. DNA analysis revealed the isochromosome to be paternal in origin, whilst the other two foetal chromosomes 12 were maternal, part iso- and part heterodisomy. Conclusion The cytogenetic and DNA constitution of the foetus indicated the isochromosome 12p to be of paternal origin, and implied post-zygotic formation of the isochromosome 12p in the Pallister–Killian syndrome. Copyright © 2004 John Wiley & Sons, Ltd.

Summary Pallister–Killian syndrome is characterized by tetrasomy of the short arm of chromosome 12p, which produces mental retardation of varying degrees and dysmorphic characteristics. We describe anaesthesia in a 2-year-old child affected by this syndrome who underwent surgery for orchidopexy. Anaesthetic consisted of an inhalation mixture of O2, N2O and sevoflurane, together with an inguinal block with ropivacaine and administration of alfentanil plus ketorolac. Tracheal intubation was uneventful. No complications of any type were observed.

CVS direct preparations usually achieve limited resolution and are better at detecting numerical rather than structural abnormalities. A CVS direct preparation analyzed using G-banding revealed a 47,XY,+G karyotype in 5 of 11 cells and was reported as mosaic for trisomy 21. Subsequent analysis of the CVS culture found only normal male cells. Amniocentesis revealed both normal male cells and cells with an extra F-group chromosome. Fluorescence in situ hybridization (FISH) identified this chromosome to be an isochromosome from the short arm of chromosome 12 [i(12)(p10)]. The amniocyte karyotype was reported as 47,XY,+i(12)(p10)[12]/46,XY[8].ish i(12)(p10)(wcp12+), which is associated with Pallister–Killian syndrome. Reexamination of the CVS direct preparation by FISH with a chromosome 12 centromere probe confirmed the karyotype of this tissue to be 47,XY,+mar[5]/46,XY[6].nuc ish 12cen(D12Z3 × 3)/12cen(D12Z3 × 2). Thus, multiple studies, including amniocentesis and fluorescence in situ hybridization, may be required to fully and accurately evaluate abnormalities detected by CVS. This case also indicates that mosaicism for supernumerary isochromosomes may have a complex origin. Copyright © 2003 John Wiley & Sons, Ltd.

Pallister-Killian syndrome is a rare disorder characterised by a specific combination of anatomic anomalies, mental retardation and lack of speech acquisition due to tetrasomy 12p. Hearing loss does not seem to be characteristic for this syndrome, although it was reported in several cases. We present the case of a girl first seen in our department at the age of 6 months. A severe sensory hearing loss was confirmed by subjective and objective audiometry. The child was successfully equipped with hearing aids. In the literature almost all children with Pallister-Killian syndrome are described as not developing verbal speech. Surprisingly their hearing abilities were not examined systematically. We advise audiological testing of children with Pallister-Killian syndrome.

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.

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.

Cytogenetic analysis in a girl with multiple congenital anomalies indicating Pallister-Killian syndrome (PKS) showed a supernumerary marker chromosome in 1/76 lymphocytes and 34/75 fibroblast metaphases. GTG-banding pattern was consistent with the chromosomal region 12pter-12q11. While fluorescence-in-situ hybridisation (FISH) with a whole chromosome 12 painting probe confirmed the origin of the marker, a chromosome 12 specific alpha-satellite probe did not hybridise to it. FISH analysis with a specific subtelomeric probe 12p showed hybridisation to both ends of the marker chromosome. High-resolution multicolour-banding (MCB) studies revealed the marker to be a der(12)(pter-->p12.3::p12.3-->pter). Summarising the FISH information, we defined the marker as an inverted duplication of 12pter-12p12.3 leading to partial tetrasomy of chromosome 12p. In skin fibroblasts, cultured at the patient's age of 1 year and 9 years, the marker chromosome was found in similar frequencies, even after several culture passages. Therefore, we consider the marker to have a functional centromere although it lacks detectable centromeric alpha-satellite sequences. To the best of our knowledge, this is the first proven analphoid marker of chromosome 12. Molecular genetic studies indicated that this marker is of paternal origin. The finding of partial tetrasomy 12pter-12p12.3 in our PKS patient allows to narrow down the critical region for PKS.

This report describes a new finding of iris transillumination defects in Pallister–Killian syndrome, a rare multi-system disorder resulting from mosaic tetrasomy of the short arm of chromosome 12. [J Pediatr Ophthalmol Strabismus 2010;47:58–59.]

We report a stillborn female infant with multiple internal and external anatomic abnormalities and mosaicism for isochromosome 12p. These abnormalities included webbed neck, low-set ears, lower jaw tooth bud, left simian crease, shield chest, focal aplasia cutis, diaphragmatic hernia, hypoplastic lungs, agenesis of pericardium, and Meckel's diverticulum. Karyotypic analysis on cord blood lymphocytes showed 10% mosaicism of 46,XX/47,XX, + i(12p), and analysis of skin fibroblasts showed 50% mosaicism for the same karyotype. The parental karyotypes were normal. There are many reported cases describing the anomalies seen in isochromosome 12p. None of these cases, however, have displayed pericardial agenesis or aplasia cutis. The clinical and cytogenetic features of Pallister-Killian syndrome are reviewed.

The Pallister-Killian syndrome is a rare disorder, which is clinically diagnosed and usually confirmed by the detection of mosaicism for an isochromosome 12p in fibroblast cultures. To date FISH on buccal mucosa has been used in only three cases and this detected high levels of mosaicism for the isochromosome. We review one previously reported case [Woodman et al. (1995) Genet Couns 6:33-36] and report a further seven clinically suspected cases in which the diagnoses were confirmed by FISH on buccal mucosa, and recommend that this tissue be used routinely for laboratory confirmation. The presence of the isochromosome 12p at levels as low as 1% is acceptable.

The Pallister-Killian syndrome (PKS) represents a rare polymalformative complex characterized by a tissue-specific mosaic distribution of an additional isochromosome 12p and characterized by diaphragmatic hernia, rhizomelic limb shortening, facial anomalies and, rarely, acral hypoplasia. Since diaphragmatic hernia and acral hypoplasia can be also found in Fryns syndrome, the differential diagnosis between the two conditions depends on the demonstration of the 12p isochromosome by FISH. Prenatal diagnosis of PKS has been reported in cases submitted to karyotyping due to advanced maternal age or congenital anomalies detected on second trimester ultrasound. Among the ultrasound-detected malformations, little attention has been paid to facial anomalies. We describe a case in which PKS was prospectively suspected on the basis of the various anomalies detected at ultrasound, namely diaphragmatic hernia, rhizomelic limb shortening, and abnormal facial profile. The diagnosis was then confirmed by FISH on amniocytes and peripheral lymphocytes. In the present case, the disclosure of typical facial abnormalities significantly contributed to the differentiation between PKS and Fryns syndrome.

The first prenatal diagnosis of Pallister-Killian syndrome by chorionic villus sampling is presented. Fetal hydrops was noted on ultrasound in early pregnancy, and the karyotype revealed isochromosome 12p mosaicism.

1. Louis P. Halamek, MD* 2. Yasser Y. El-Sayed, MD† 1. 2. *Division of Neonatal and Developmental Medicine, Department of Pediatrics. 3. 4. †Division of Maternal-Fetal Medicine, Department of Gynecology and Obstetrics, Stanford University School of Medicine, Palo Alto, CA. After completing this article, readers should be able to: 1. Describe the incidence of congenital diaphragmatic hernia (CDH). 2. Delineate what percent of all CDHs occur on the left hemithorax and what percent are associated with the presence of other malformations. 3. Describe the mortality rate for prenatally diagnosed CDH and what factors affect the presence of associated malformations and chromosomal defects and are the major determinants of mortality. 4. Describe optimal prenatal counseling for a woman carrying a fetus who has CDH. The incidence of congenital diaphragmatic hernia (CDH) is reported to be approximately 1 in 2,000 to 4,000 births. It is believed to result from incomplete fusion of the pleuroperitoneal membrane and passage of abdominal contents into the chest. The small bowel, stomach, spleen, and colon are the most frequently herniated organs, although pancreas, liver, adrenal glands, and kidneys also have been found. Approximately 90% of all CDHs occur on the left hemithorax, and up to 50% of cases are associated with the presence of other malformations. CDH may be one component of recognized multiple malformation complexes, including chromosomal disorders (trisomy 13, trisomy 18, trisomy 21, tetraploidy, Pallister Killian syndrome [tetrasomy 12 p mosaicism], and Turner syndrome), single gene disorders (Fryn syndrome), and others for which the genetic etiology is uncertain (laterality sequence). Abnormalities in numerous organs other than the lungs have been described, including the heart, kidneys, gastrointestinal tract, abdominal wall, and central nervous system. In addition to more common forms of congenital heart disease, such as tetralogy of Fallot and truncus arteriosus, diminished left ventricular mass has been noted in a number of patients who have left-sided CDH and may have an impact on mortality. The prognosis of CDH is poor, especially for infants in whom the diagnosis is made in utero. The especially poor prognosis for infants diagnosed in …

We describe a case of Pallister-Killian syndrome ascertained by routine amniocentesis as i(12p). The i(12p) was also found in 4 tissues of the aborted fetus, where various degrees of mosaicism 46/47 + i(12p) were seen. Although autopsy showed no major malformations, some of the minor anomalies of Pallister-Killian syndrome were found.

A pregnant woman was referred to our hospital at the 29th week of gestation with the symptom of polyhydramnios; diaphragmatic herniation of the fetus was suspected. Fetal chromosome anlaysis was performed using fibroblasts obtained by aminocentesis, and mosaicism of 46,XX and isochromosome of 12p were diagnosed. Out of 50 karyotyped cells, 19 (38.0%) showed the tetrasomy of the isochromosome of 12p. The mother vaginally delivered a baby girl who died just after delivery. The analysis of cord blood lymphocytes revealed only 0.5% incidence of tetrasomy of 12p. The incidence of tetrasomy was 8.0% for the placental chorionic villi, 48.0% for the fibroblasts obtained from the umbilical cord, and 70.0% for the skin fibroblasts. Thus, the diagnosis of Pallister-Killian Syndrome (PKS) is confirmed by mosaicism of i(12p), that is, the affected patients exhibit tissue-specific mosaicism, with the abnormal karyotype expression in limited lymphocytes, but marked in fibroblasts.

Pallister-Killian syndrome is a rare disorder comprising multiple congenital anomalies, streaks of hypo(hyper)pigmentation, seizures, profound mental retardation, and the presence of an extra metacentric chromosome i(12)(p10), usually limited to skin fibroblasts. The mechanism and parental origin of the extra chromosome i(12)(p10) are unknown. Here, we present a girl with Pallister-Killian syndrome and the i(12)(p10) in 50% of cultured skin fibroblasts. Using microsatellite DNA markers of chromosome 12p, we detected 3 alleles--including 2 different alleles of maternal origin--in cultured skin fibroblasts, suggesting that the tetrasomy 12p is the result of a prezygotic event, with a nondisjunction event during maternal meiosis.

We report on a boy with Pallister-Killian syndrome (PKS) who was conceived by assisted reproductive technology (ART), specifically in vitro fertilization (IVF) with parents' gametes. A prenatal diagnosis performed elsewhere by CVS failed to detect the presence of the isochromosome 12p that was demonstrated postnatally in approximately 50% of cultured skin fibroblasts. Given that the patient did not show the congenital overgrowth typical of PKS, we speculate that ART might have restricted overgrowth in this particular case. More broadly, we hypothesize that overgrowth might protect from early demise fetuses conceived by ART, a technology known to cause low and very low birth weight.

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.

The Pallister-Killian syndrome is a rare cytogenetic condition first described in 1977 by Pallister et al. in 3 adults; the first affected child was reported in 1981. This syndrome (also known as Pallister mosaic aneuploidy syndrome or isochromosome 12p mosaicism) is characterized by postnatal growth retardation, seizures, hypotonia, deafness, profound mental retardation, minimal speech development, and a distinctive facial appearance (high prominent forehead, ocular hypertelorism, sparse anterior scalp hair, prominent lower lip, large ears with thick protruding lobules, cupid-bow shaped upper lip, and a long philtrum). A chromosome 12 abnormality (tetrasomy 12p) has been reported in skin biopsies from these patients but this chromosome anomaly is usually not found (or in only a small proportion, e.g.

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.

The diagnosis of Pallister-Killian syndrome (PKS) is confirmed by tissue-specific mosaicism of i(12p). The isochromosome is found in skin fibroblasts and bone marrow, but rarely in peripheral lymphocytes. The nature of the isochromosome loss was evaluated using 2 techniques: micronucleus formation for anaphase lag and in situ DNA hybridization for mosaicism in interphase cells. Cells from serial cultured fibroblasts, peripheral blood lymphocytes, and bone marrow from 4 PKS patients were used for the above analysis. Micronucleus formation was similar for PKS and normal diploid cultures, ruling out loss of i(12p) by anaphase lag as the major mechanism of in vitro mosaicism. In situ hybridization using an alpha satellite DNA probe for chromosome 12 was used to examine the presence of the i(12p) in interphase fibroblasts from 1 patient and lymphocytes from 2 patients (age 8 weeks and 1 day). The i(12p) was present in a significantly higher proportion of interphase nuclei in peripheral lymphocytes than in metaphase, suggesting the initial loss of the isochromosome is exaggerated in metaphase by selective division in vitro. In situ hybridization of peripheral lymphocyte interphase cells with chromosome 12 specific probes may be a useful supplemental procedure for the diagnosis of PKS, at least in the newborn infant.