Mild phenotype in a 15-year-old boy with Pallister-Killian syndrome

Case Report: Early Neonatal EEG in Two Infants with Pallister Killian Syndrome (PKS)

Pallister Killian Syndrome (PKS) is a rare genetic disorder caused by a mosaic tetrasomy of the short arm of chromosome 12. The syndrome is characterised by typical craniofacial dysmorphism, congenital anomalies and intellectual disability. Epilepsy is a known complication, with onset usually occurring in early childhood and characterised most commonly by spasms and myoclonic seizures. To the best of our knowledge, there have been no cases describing the early neonatal EEG in PKS and  electrographic seizures, to date. Here, we report two cases of PKS presenting in the neonatal period with distinctive EEG features and seizures.

Cognitive, Behavioral, and Sensory Profile of Pallister–Killian Syndrome: A Prospective Study of 22 Individuals

Background: Developmental delay and intellectual disability are two pivotal elements of the phenotype of Pallister–Killian Syndrome (PKS). Our study aims to define the cognitive, adaptive, behavioral, and sensory profile of these patients and to evaluate possible correlations between the different aspects investigated and with the main clinical and demographic variables. Methods: Individuals of any age with genetically confirmed PKS were recruited. Those ≤ 42 months were administered the Bayley Scales of Infant and Toddler Development Third Edition (Bayley-III), and those > 42 months the Vineland Adaptive Behavior Scales—Second Edition (Vineland-II). Stereotyped behaviors (Stereotypy Severity Scale, SSS) and aggressive behaviors (Behavior Problems Inventory—Short Version, BPIs) were assessed in all subjects > 1 year; sensory profile (Child Sensory Profile 2, C-SP2) in all aged 2–18 years. Results: Twenty-two subjects were enrolled (11 F/11 M; age 9 months to 28 years). All subjects ≤ 42 months had psychomotor developmental delay. Of the subjects > 42 months, 15 had low IQ deviation, and 1 in the normal range. Stereotypies were frequent (median SSS-total score 25/68). Lower Vineland-II values corresponded to greater intensity and frequency of stereotypies (p = 0.004 and p = 0.003), and self-injurious behaviors (p = 0.002 and p = 0.002). Patients with severe low vision had greater interference of stereotypies (p = 0.027), and frequency and severity of aggressive behaviors (p = 0.026; p = 0.032). The C-SP2, while not homogeneous across subjects, showed prevalence of low registration and sensory seeking profiles and hypersensitivity to tactile and auditory stimuli. Lower Vineland-II scores correlated with higher Registration scores (p = 0.041), while stereotypies were more frequent and severe in case of high auditory sensitivity (p = 0.019; p = 0.007). Finally, greater sleep impairment correlated with stereotypies and self-injurious behaviors, and lower Vineland-II scores. Conclusions: The present study provides a further step in the investigation of the etiopathogenesis of the syndrome. Furthermore, these aspects could guide rehabilitation therapy through the identification of targeted protocols.

Case Report: A Case Study on the Neurodevelopmental Profile of a Child With Pallister-Killian Syndrome and His Unaffected Twin

Pallister-Killian syndrome is an uncommon genetic disorder that has broad developmental and multisystemic effects. While medical complications are widely reported throughout the literature, research on the neurodevelopmental profile has been limited. Case reports make up the majority of the few existing studies regarding the neurodevelopmental phenotype associated with this disorder. The current case report describes a 3-year-old male with Pallister-Killian syndrome (AF), reports the neurodevelopmental evaluation of his unaffected twin brother (MF), and outlines the results of an optical imaging study on both boys. AF presents with severe developmental delays, however, he ambulates with support and engages in conversation using his communication device. Most severely impaired was AF's speech and expressive language, with childhood apraxia of speech (CAS) as a possible explanation for these severe deficits. MF, the sibling, demonstrated neurotypical abilities and often advanced scores for his age. Both subjects completed a functional near-infrared spectroscopy (fNIRS) study, revealing decreased temporal and frontal lobe function in AF and typical functioning in MF. This case report expands on the existing literature on PKS by describing variances in fraternal twin presentation and novel reporting on fNIRS findings in both boys.

Prenatal diagnosis of Pallister-Killian syndrome and literature review

Pallister‐Killian syndrome (PKS) is a rare sporadic genetic disorder usually caused by mosaicism of an extra isochromosome of 12p (i(12p)). This retrospective study analysed the prenatal ultrasound manifestations and molecular and cytogenetic results of five PKS foetuses. Samples of amniotic fluid and/or cord blood, skin biopsy and placenta were collected. Conventional karyotyping and single nucleotide polymorphism array (SNP array) were performed on all the amniotic fluid or cord blood samples. Copy number variants sequencing (CNV‐seq) and fluorescence in situ hybridization (FISH) were also used for the validation for one foetus. All the five foetuses were from pregnancies with advanced parental age. Two foetuses involved structural abnormalities and one foetus had only soft markers, all of which included increased nuchal translucency. The rest two foetuses had normal ultrasounds in the second trimester, which has rarely been reported before. The karyotype revealed typical i(12p) in four cases and a small supernumerary marker chromosome consisting of 12p and 20p in the remaining one case. The proportion of cells with i(12p) ranged from 0 to 100% in cultural cells, while SNP array results suggested 2−4 copies of 12p. For one foetus, metaphase FISH showed normal results, but the interphase FISH suggested cell lines with two, three and four copies of 12p in the amniotic fluid. Advanced parental age may be an important risk factor for PKS, and there were no typical ultrasound manifestations related to PKS. A combination of karyotype analysis and molecular diagnosis is an effective method for the diagnosis of PKS.

First Case Report of Maternal Mosaic Tetrasomy 9p Incidentally Detected on Non-Invasive Prenatal Testing

Tetrasomy 9p (ORPHA:3390) is a rare syndrome, hallmarked by growth retardation; psychomotor delay; mild to moderate intellectual disability; and a spectrum of skeletal, cardiac, renal and urogenital defects. Here we present a Chinese female with good past health who conceived her pregnancy naturally. Non-invasive prenatal testing (NIPT) showed multiple chromosomal aberrations were consistently detected in two sampling times, which included elevation in DNA from chromosome 9p. Amniocentesis was performed and sent for chromosomal microarray, which was normal. Maternal karyotype revealed that mos 47,XX,+dic(9;9)(q21.1;q21.1)(24)/46,XX(9) presents mosaic tetrasomy for the short arm of chromosome 9p and is related to the NIPT results showing elevation in DNA from chromosome 9p. The pregnancy was uneventful, and the patient was delivered at term. Maternal samples were obtained at two different time points after delivery showed the same multiple chromosomal aberrations detected during pregnancy. This is a first report on an unusual case of mosaic isodicentric tetrasomy 9p in a healthy adult with normal intellect. With widespread adoption of NIPT for screening fetal aneuploidy and genome-wide copy number changes, a rise in incidental detection of maternal rare genetic syndrome will bring challenges in our current approach to genetic counselling and prenatal diagnosis.

Pallister-Killian Mosaic Syndrome in an Omani Newborn: A Case Report and Literature Review

Pallister-Killian mosaic syndrome (PKS) is a rare sporadic condition with multiple congenital anomalies and intellectual deficits caused by mosaic tissue-limited tetrasomy of the short arm of chromosome 12 (12p). The clinical features are highly variable, ranging from mild to severe. Diagnosis is usually missed because of the low level of mosaicism in peripheral lymphocytes. We present a case of an Omani newborn with PKS with severe clinical presentation and multisystem involvement that lead to postnatal death. Karyotype and fluorescent in situ hybridization studies confirmed the presence of chromosome 12p duplication. This is the first case of PKS reported in the literature from Oman and the Arab world.

Pallister-Killian syndrome: clinical, cytogenetic and molecular findings in 15 cases

Background

Pallister Killian syndrome (PKS, OMIM 601803) is a rare genetic disorder with a distinct phenotype caused by tissue- limited mosaicism tetrasomy of the short arm of chromosome 12, which usually cytogenetically presents as an extra isochromosome 12p.Wide phenotypic variability in PKS has been reported, ranging from pre-to perinatal death due to multiple congenital anomalies, especially diaphragmatic hernia, and classic phenotypes including seizures, severe developmental delay, macrosomia at birth, deafness, and distinct dysmorphic features, such as coarse face, temporal alopecia, a small nose with anteverted nostrils, long philtrum, and hypo-/hyper- pigmented streaks on the skin.

Results

Karyotypes obtained from cultured peripheral lymphocytes of 13 cases, who were diagnosed as PKS, were normal, while karyotypes obtained from cultured skin samples and buccal mucosa revealed the supernumerary mosaic i(12p). Mosaic karyotype was found in both fibroblast and buccal mucosa in 14 of 15 patients in our series, whereas in one stillbirth, following the clinical diagnosis of PKS, skin and buccal smear samples were taken, and all karyotypes from cultured fibroblasts revealed a supernumerary i(12p), while I-FISH study showed 60% mosaicism in mucosal cells.

Conclusions

We here share the clinical, cytogenetic and molecular cytogenetic findings of 15 cases with PKS phenotype and the parental origin of seven i(12p) identified by molecular analyses. To our knowledge, this is the largest series of PKS patients with parental origin study from a single center. We believe that our study makes a significant contribution to the literature because we specifically found no differences in the phenotypes of cases with either a maternal or paternal origin of the extra element and differential imprinting appeared not to be a factor.

Cytogenomic delineation and clinical follow-up of 10 Brazilian patients with Pallister-Killian syndrome

Background

Pallister-Killian syndrome (PKS) is a sporadic genetic disorder caused by the presence of a tissue-specific mosaicism for isochromosome 12p - i(12) (p10) and is characterized by facial dysmorphism including coarse facies, upslanting palpebral fissures, bitemporal alopecia, pigmentary skin anomalies, developmental delay, hypotonia and seizures. Although typical clinical features of PKS commonly exist, clinicians often do not raise the possibility of this diagnosis.

Results

We reviewed the medical records of 10 patients with confirmed PKS followed in our service (since 1990 to 2015). Age at diagnosis varied from prenatal to 3 years and clinical features were consistent with those described in the literature. In all patients, peripheral blood karyotypes were normal and cytogenomic study was performed in order to confirm the diagnosis. Three of these patients had PKS diagnosis confirmed by buccal smear MLPA.

Conclusion

An early conclusion from our results demonstrated that MLPA on buccal smears is a good and non-invasive method to detect extra copies of 12p and should be considered as the first exam, before a skin biopsy for a fibroblast karyotype is performed.

Pallister-Killian syndrome: a study of 22 British patients

BACKGROUND

Pallister-Killian syndrome is a rare, sporadic condition caused by mosaic tetrasomy of the short arm of chromosome 12 (12p). The main features are intellectual disability, seizures, dysmorphic features and a variety of congenital malformations. Most available information comes from individual case reports. We report the results of a British study into Pallister-Killian syndrome, which is the first to provide comprehensive data on a population-based sample.

METHOD

A detailed phenotypical study was carried out in Great Britain. All individuals with Pallister-Killian syndrome were eligible to participate. Each participant underwent a structured history, developmental assessment and clinical examination. Buccal mucosal samples were analysed by interphase fluorescence in situ hybridization (FISH) and blood samples by array comparative genomic hybridization (CGH). Genotype-phenotype correlations were sought in these tissues and existing skin biopsy reports.

RESULTS

Twenty-two patients with Pallister-Killian syndrome, ranging from 4 months to 31 years were recruited and comprehensive data on each obtained. The birth incidence was 5.1 per million live births. Array CGH only suggested the diagnosis in 15.8% but buccal FISH could have made the diagnosis in 75.0%. There was no genotype-phenotype correlation in any of the tissues studied. This study shows that the high birth weights and profound intellectual disability classically described in Pallister-Killian syndrome are not universal. Mild or moderate intellectual disability was present in 27.6% of this cohort and all birth weights were within 2.67SD of the mean. New features which have not previously been recognised as part of Pallister-Killian syndrome include anhydrosis/hypohydrosis and episodic hyperventilation, suggesting involvement of the autonomic system.

Developmental and behavioral characteristics of individuals with Pallister-Killian syndrome

Pallister-Killian syndrome is a sporadic disorder caused by the presence of mosaic tetrasomy of the short arms of chromosome 12. Case reports of children with Pallister-Killian syndrome have described a range of developmental and behavioral outcomes, but no systematic studies of these outcomes exist. The objective of this study was to describe developmental and behavioral characteristics of individuals with Pallister-Killian syndrome participating in a national meeting of families and their affected children. Sixteen individuals with Pallister-Killian syndrome, ages 16 months to 19 years, were studied using questionnaires and direct interview. Among the 16 patients enrolled in the study, 3 probands were between 16 and 19 months, and had severe developmental delay. Among the rest of the 13 probands older than 24 months, 11 children had a developmental level of less than 8 months age equivalent. They were non-ambulatory, non-verbal, and passive, requiring extensive assistance in daily living. There were two higher functioning children who were ambulatory, and verbal. One of these children met criteria for Autism on the Autism Diagnostic Interview-Revised. Thus, although most individuals with Pallister-Killian syndrome studied showed profound intellectual disability and sensory impairments, individuals with Pallister-Killian syndrome can have mild to moderate intellectual disability. Therefore, in individuals with physical examination findings of Pallister-Killian syndrome, formal diagnostic testing should be considered, even in individuals with mild to moderate intellectual disability. Further studies will be needed to determine if these higher functioning children with Pallister-Killian syndrome are at increased risk for autism.

Novel clinical manifestations in Pallister-Killian syndrome: comprehensive evaluation of 59 affected individuals and review of previously reported cases

Pallister-Killian syndrome is a rare, multi-system developmental diagnosis typically caused by tetrasomy of chromosome 12p that exhibits tissue-limited mosaicism. The spectrum of clinical manifestations in Pallister-Killian syndrome is wide and includes craniofacial anomalies, clefts, ophthalmologic, audiologic, cardiac, musculoskeletal, diaphragmatic, gastrointestinal, genitourinary, and cutaneous anomalies in association with intellectual disability and seizures. Growth parameters are often normal to elevated at birth with deceleration of growth postnatally. No formal estimate of the prevalence of Pallister-Killian syndrome has been made. Here, we report the clinical findings in 59 individuals with Pallister-Killian syndrome who were ascertained at Pallister-Killian syndrome Foundation family meetings held in the summers of 2006, 2008, 2009, and 2010. In addition, the clinical findings of 152 cases reported in the medical literature were reviewed and compared to the cohort examined here. Several novel clinical characteristics were identified through detailed dysmorphology examinations of this cohort and reassertion of a mild developmental variant is described. This report expands the clinical manifestations of Pallister-Killian syndrome and highlights the variable expressivity of this diagnosis with important implications for diagnosis and counseling.

Seizures and EEG patterns in Pallister-Killian syndrome: 13 new Italian patients

BACKGROUND AND OBJECTIVES

Pallister-Killian syndrome (PKS) is a rare genetic disorder caused by a tissue-limited mosaic supernumerary isochromosome 12p. Typical facial dysmorphisms, pigmentary abnormalities, and some major malformations are frequently present. Neurological manifestations include mental retardation, hypotonia, and seizures. Epilepsy incidence ranged from 39 to 59% in a previously reported series. No specific clinical and EEG phenotype has ever been reported to describe seizure features, electroclinical patterns, and response to therapy in PKS.

METHODS

This was a multicentre study conducted on 13 Italian children with PKS, as diagnosed by clinical phenotype and confirmed in cultured fibroblasts. All patients underwent several polygraphic video-EEG recordings and brain magnetic resonance imaging.

RESULTS AND CONCLUSIONS

All the patients presented with epilepsy and seizures that started at a mean age of 19 months. In six cases, epilepsy started with epileptic spasms (ES) combined with focal seizures in another case. In four cases, seizures were focal, and this was followed by ES in two patients. In only two cases, epilepsy started with myoclonic seizures, and spasms were never observed. The study provides further evidence that epilepsy is a part of the phenotype of PKS, although a specific clinical and EEG pattern could not be identified. Our cases show how ES with late- or first-year onset is the most common type of seizure. Despite a variable prognosis in terms of response to therapy, a significant proportion of patients achieved good seizure control.

Tetrasomy 9p mosaicism associated with a normal phenotype in two cases

Tetrasomy 9p is a rare chromosomal syndrome and about 30% of known cases exhibit mosaicism. Approximately 50 of the reported cases with tetrasomy 9p mosaicism show a characteristic facial appearance, growth failure, and developmental delay. However, 3 patients with mosaicism for isochromosome 9p and a normal phenotype have also been reported. We report 2 additional cases of clinically normal young females with tetrasomy 9p mosaicism, one of whom also exhibited X chromosome aneuploidy mosaicism leading to an overall of 6 different cell lines. STR analysis performed on this complex mosaic case indicated that the extra isochromosome was of maternal origin while the X chromosome aneuploidy was of paternal origin, indicating a postzygotic event.

Pallister-Killian syndrome in a girl with mild developmental delay and mosaicism for hexasomy 12p

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.

Pallister-Killian syndrome caused by mosaicism for a supernumerary ring chromosome 12p

Pallister-Killian syndrome (PKS) is a rare but distinctive chromosomal syndrome distinguished by severe intellectual impairment, characteristic facial features, and variable structural anomalies. The characteristic cytogenetic abnormality in PKS is a supernumerary isochromosome 12p that confers mosaic tetrasomy. We describe a female child with PKS in whom tetrasomy 12p resulted from a supernumerary ring chromosome containing two copies of chromosome 12cen --> p13, a novel cytogenetic finding. The ring chromosome exhibited tissue-limited mosaicism, being absent in blood but detected in 38% of buccal mucosa cells and 41% of skin fibroblasts. Our patient demonstrated the typical dysmorphic characteristics of PKS, but her development was relatively advanced in comparison to children with isochromosome PKS. Her milder developmental phenotype may be attributable to differences in the mosaic distribution or the genomic content of the ring chromosome compared to mosaic isochromosome 12p.

Pallister-Killian syndrome: tetrasomy of 12pter→12p11.22 in a boy with an analphoid, inverted duplicated marker chromosome

Supernumerary marker chromosomes (SMCs) without detectable alphoid DNA are predicted to have a neocentromere and have been referred to as mitotically stable neocentromere marker chromosomes (NMCs). Here we report the molecular cytogenetic characterization of a new case of Pallister-Killian syndrome (PKS) in a boy with an analphoid, inverted duplicated NMC derived from 12pter-->12p11.22 in his fibroblasts by using high-resolution comparative genetic hybridization (HR-CGH), multiplex fluorescent in situ hybridization (FISH) and bacterial artificial chromosome (BAC)-FISH mapping analyses with various alpha-satellite DNA probes, subtelomere probes and BAC-DNA probes. Precise identification of SMCs and NMCs is of essential importance in genetic counseling. HR-CGH is a more informative and often a faster way of precisely identifying the origin of SMCs. This case is the third report of PKS with an NMC containing an inverted duplication of partial 12p with available clinical data. These observations may help to determine the critical region for PKS and the mechanisms leading to the origin of the NMC derived from 12pter-->12p11.22 - a region that appears to be susceptible to the formation of neocentromeres. The use of subtelomeric probe PCP12p in buccal cells appears superior to the use of the centromere probe D12Z3 for the diagnosis of the PKS.

Retrospective Diagnosis of Pallister-Killian Syndrome by CGH Array

OBJECTIVE AND METHODS

We report a girl presenting with a polymalformation syndrome. Despite a normal karyotype on peripheral lymphocytes and the unavailability of cultured fibroblasts, a tetrasomy 12p was identified on pulmonary DNA extracted from a postmortem biopsy, by use of comparative genomic hybridization (CGH) and confirmed by CGH array. The clinical picture of our patient was consistent, but not specific of the diagnosis of Pallister-Killian syndrome. She presented with the association of antenatal polyhydramnios, craniofacial dysmorphic features, skeletal abnormalities, and a congenital cardiopathy.

CONCLUSION

We discuss the usefulness of CGH and CGH array in prenatal and constitutional cytogenetics.

Pallister-Killian syndrome: Multiband FISH of tetrasomy 12p

Two patients with mosaicism for tetrasomy 12p are described. One was diagnosed at the age of 14 years with severe mental retardation and other dysmorphologic findings and abnormal skin pigmentation. Chromosome analysis of a blood sample showed a normal female karyotype. A skin biopsy specimen showed mosaicism for a marker chromosome. The other patient was diagnosed prenatally, from a chorionic villus sample, but only in the direct preparation. Mosaicism for a marker chromosome was demonstrated. The ultrasound examination revealed no abnormalities. Multicolor and multiband fluorescence in situ hybridization analyses showed that the marker chromosome was derived from chromosome 12p, which confirmed the diagnosis of Pallister-Killian syndrome in both patients. To our knowledge, this is the first report of the use of these fluorescence in situ hybridization techniques in Pallister-Killian syndrome whereby the nature of the marker chromosome could be confirmed to be derived from chromosome 12p.

Pallister-Killian syndrome (PKS): clinical case report

Pallister-Killian Syndrome is a rare dysmorphic condition characterized by specific clinical manifestations and tetrasomy 12p. This paper focuses on the general and orofacial clinical manifestations.

High cognitive functioning and behavioral phenotype in 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.