6'Med Genet 1995;32:68-71

Pallister-Killian syndrome: normal karyotype inprenatal chorionic villi, in postnatallymphocytes, and in slowly growing epidermalcells, but mosaic tetrasomy 12p in skinfibroblasts

D Horn, F Majewski, B Hildebrandt, H Korner

AbstractWe report on two patients with Pallister-Kilman syndrome: an 18 month old maleinfant followed since the neonatal periodand a 4 year old boy. Prenatal diagnosisby chorionic villi sampling (CVS) in thefirst case showed a normal karyotype with-out mosaicism. Chromosome analysis onperipheral lymphocytes of the newbornalso showed a normal karyotype. The clin-ical diagnosis of Pallister-Killian syn-drome was made after the first year of lifebecause of the typical facial dysmorphismand other characteristic clinical features,such as frontotemporal alopecia, de-pigmented area of the skin, sensorineuralhearing loss, and severe psychomotor re-tardation. Chromosome analysis fromskin fibroblasts now showed an iso-chromosome 12p mosaicism. The originof the extra chromosome was confirmedby in situ hybridisation using a chro-mosome 12 specific library. In the secondcase chromosomal analysis from peri-pheral lymphocytes at the age of 19 monthsshowed a normal karyotype 46,XY. Fol-lowing the clinical diagnosis of Pallister-Killian syndrome a superficial skin biopsywas performed which showed very poorand slow growth of cells and a normalkaryotype. Because of the typical symp-toms a larger and deeper skin biopsy wasperformed from which there was rapidgrowth of fibroblasts. Now the diagnosiswas established on the basis ofthe presenceof an i(12p) extra chromosome in 69% ofthe metaphases.

(JMed Genet 1995;32:68-71)

Pallister-Killian syndrome is caused by te-trasomy 12p mosaicism. The isochromosome12p is rarely found in cultured lymphocytes inthe newborn, but mainly in skin fibroblasts orbone marrow cells. In younger children thissyndrome is characterised by typical cranio-facial dysmorphic features, including fronto-temporal alopecia, sparse eyebrows, hyper-telorism, flat nasal bridge and a shortened nose,large mouth with downturned corners, severemental retardation, pigmentary anomalies ofthe skin, brachydactyly, and the occurrence

of diaphragmatic defects and congenital heartdefects.' Older children with Pallister-Killiansyndrome present a different phenotype withnormal distribution of hair, macroglossia, pro-gnathism, seizures, and profound mental re-tardation.2 Prenatal diagnosis of tetrasomy 12pby CVS and amniocentesis has been doc-umented in several cases.3 8 The iso-chromosome 12p in amniotic cells andchorionic cells in most of these cases was ob-served in all or nearly all cells.

Case reportsCASE 1 (BERLIN)Prenatal diagnosis by CVS, requested by a 45year old German mother and her 48 year oldGerman husband, showed a normal karyotype,46,XY. The family history was unremarkable.Pregnancy was complicated by poly-hydramnios. Spontaneous delivery occurred inthe 36th week of pregnancy. Birth weight was2870 g, length 49 cm, and OFC 36 cm. Dys-morphic features noted were a prominent me-topic suture, short palpebral fissures, a shortnose with depressed bridge and antevertednares, simple and elongated philtrum, a largemouth, bifid uvula, receding chin, and dorsallyrotated ears (fig lA, B). A short neck withexcessive nuchal skin, widely spaced nipples,and undescended testes were noted. The upperand lower limbs and the hands and feet wereshort. Ulnar deviation of all fingers (fig 1C)and simian creases were observed as well as aventricular septal defect. Radiological ex-amination showed brachydactyly and dis-location of the heads of the radii. Chromosomeanalysis on peripheral lymphocytes showed anormal karyotype, 46,XY.At 10 months of age the boy was 71 cm long

(1Oth centile), weighed 8 kg (1Oth centile), andhad an OFC of43 cm (<3rd centile) (fig 2). Theocciput and face were now flat. Temporofrontalalopecia, depigmentation over the right eye-brow, a shallow upper orbital ridge, hy-pertelorism, and ptosis were obvious. Themouth was large with downturned corners(fig 2A, B). No teeth had emerged. Oph-thalmological examination showed nystagmusand exophoria. The ulnar deviation of the fin-gers with the exception of the index finger hadresolved. Profound motor and mental re-

Institute of MedicalGenetics, School ofMedicine (Charite),Humboldt University,Luisenstrasse 13,D-10098, Berlin,GermanyD HornH Korner

Institute of HumanGenetics andAnthropology,Heinrich-HeineUniversity,Dusseldorf, GermanyF MajewskiB Hildebrandt

Correspondence to:Dr Horn.Received 11 April 1994Revised version accepted forpublication 11 August 1994

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Pallister-Killian syndrome

A e f B C

Figure 1 Case 1 as newborn showing (A) short palpebral fissures, short nose, simple philtrum, large mouth, short neck,(B) small mandible, low set, dysplastic ears, alopecia of the forehead, (C) ulnar deviation of all fingers and simian crease.

tardation, generalised muscular hypotonia, andsensorineural hearing loss were noted. CerebralCT scan showed slight dilatation of the vent-ricles.

CYTOGENETIC INVESTIGATIONSSeventeen cells from the direct preparation andeight cells from cultured chorionic villi wereexamined. G banded chromosomes had a nor-mal male karyotype. Additionally, a ret-rospective investigation of 28 mitoses of thechorionic cell samples showed no evidence ofchromosomally abnormal cells. The strikingphenotype of the newborn led us to perform acytogenetic investigation of peripheral bloodlymphocytes. G banded chromosome studiesof 100 mitoses showed a normal karyotype.At the age of 18 months a skin biopsy wasperformed and was cultured in Amniomax me-dium. Karyotyping of fibroblasts showed thepresence of an isochromosome 12p in 85% of100 mitoses (fig 3A). The origin of the extrachromosome was confirmed by in situ hy-bridisation using a chromosome 12 specificlibrary (fig 3B).

B

Figure 2 Case 1 at the age of 1 year showing (A) high frontal hairline, prominentmetopic suture, depigmentation over the right eyebrow, ptosis, hypertelorism, short nosewith upturned nares, large mouth with downturned corners, and (B) temporofrontalalopecia and flat occiput.

CASE 2 (DtSSELDORF)This was the third child of healthy, unrelatedparents. Spontaneous birth occurred at 38weeks of gestation. Birth weight was 4220 g,length 54 cm, and OFC 37 cm. The boy hadalopecia of the forehead, reduced spontaneousmovements, and retarded motor and speechdevelopment. He sat at 3-5 years. At the ageof 4 years he could not speak, was unable tostand, and had no contact with his parents orother persons. We saw the boy first at the ageof 19 months, and noted a prominent glabella,marked alopecia of the forehead, and smalldepigmented areas in this region, a shortenednose, long upper lip, broad mouth, multiplefrenula at the upper alveolar ridge, large anddeep set ears, loose skin with three furtherdepigmented spots, muscular hypotonia, nofixation, and marked developmental delay.Chromosome analysis on lymphocytes

showed a normal male karyotype and we madethe tentative diagosis of Opitz trigonocephalysyndrome. When looking at the slides 20months later, we corrected our diagnosis toPallister-Killian syndrome. At re-examinationat the age of 3 years 4 months the boy was stillseverely retarded, with no further motor orspeech development. His length was 99 cm, hisweight 17 kg, and his OFC 52 cm (fig 4). Weinformed the parents of our diagnosis, butchromosomal analysis from epidermal cellsfailed to show the expected extra chromosome.Since growth of the epidermal cells was veryslow and poor and the facial aspect and thedegree of mental retardation correspondedclosely to the Pallister-Killian syndrome, weperformed a second skin biopsy when the pa-tient was 4 years old. Since this skin biopsywas deeper than the first one, there was fastand ample growth of fibroblasts.At the age of 4 years, height (102-5 cm),

weight (175 kg), and OFC (52-5 cm) werenormal. The scalp hair was now thick and curly,the frontal alopecia was less striking than atthe first examination, the nose was short, thephiltrum long, the mouth wide, and the earslarge. The enlarged tongue protruded and pro-gnathism developed which becomes more pro-nounced in adult patients.2

A i:

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Horn, Majewski, Hildebrandt, Korner

Case 1A

B

Case 2

Figure 3 Case 1. (A) G banded and graphic partial karyotype of case 1 and case 2 from skin fibroblasts. (B) Note isochromosome 12p. In situhybridisation with chromosome 12 specific library showed the presence of two normnal chromosomes 12 and the isochromosome 12p.

CYTOGENETIC INVESTIGATIONS

Chromosome analysis from peripheral lymph-ocytes showed a normal karyotype 46,XY atthe age of 19 months. At the age of 3 years 4months a superficial skin biopsy was performedand was cultured in Chang-D medium. Therewas a very slow growth of epidermal cells; thefirst harvest was done after six weeks and thesecond harvest after seven weeks. Fifty me-

Figure 4 Appearance of case 2 at the age of 3 years 4 months: high forehead withfrontotemporal alopecia, short nose, enlarged tongue, broad mouth, and large ears.

taphases were analysed, and none showed theexpected extra chromosome. At the age of 4years, a second skin biopsy was performed toa greater depth (2 mm in depth and 4 to 5 mmin diameter) and now there was a rapid growthof fibroblasts using the same cultural pro-cedure; after the first passage we now observedan i(12p) extra chromosome in 69% of themetaphases (31/45) (fig 3A).

DiscussionThe Pallister-Killian syndrome is caused by atissue specific mosaic i(12p) extra chromosomemainly in skin fibroblasts or bone marrow cells,and only rarely in lymphocytes of the newborn.Characteristic features are profound motor andmental retardation; most patients have nospeech development. In infancy there is alo-pecia of the forehead and the temporal areas,the forehead is high, the nose short, the upperlip long, and the mouth wide and downturned.The chin is receding. The tongue is enlarged,causing a protruding lower lip and in laterinfancy and adolescence marked prognathism.There may be brachydactyly and congenitalheart defects.Mosaic tetrasomy 12p was reported in seven

cases after amniocentesis which was done be-cause of advanced maternal age or ultrasoundabnormalities.357A high proportion of cells with the iso-

chromosome 12p, which is consistent with the

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Pallister-Killian syndrome

results in postnatal skin fibroblasts, was ob-served in all cases. Prenatal diagnoses ofmosaictetrasomy 12p by CVS were reported bySharland et al4 and Bresson et al.8 In both cases

a similarly high percentage of tetrasomic cellswas detected. In our case 1 with Pallister-Killian syndrome a normal karyotype in directpreparation and in long term culture of chor-ionic tissue was observed. The advanced ma-

ternal age suggests the possibility that theaneuploidy observed later in the patient re-

sulted from a meiotic error with subsequentmitotic loss ofthe isochromosome in some cellsduring embryogenesis. The normal karyotypeofthe cytotrophoblast (direct chromosome pre-

paration or short term incubation of the villi)and of the mesenchymal core of the villi (longterm culture) could be because of very earlyloss of the extra chromosome in some cells or

the fact that only a few chorionic cell clonescould be examined.The non-disjunction and the isochromosome

formation may occur postzygotically after thedifferentiation between cytotrophoblast, me-

senchymal core, and the embryo; this couldexplain the normal chromosome analysis inchorionic villi.The dysmorphism of the face suggestive of

a chromosome aberration led us to perform a

cytogenetic investigation from peripherallymphocytes with normal results in both cases.

In the reported newborn cases with the iso-chromosome 12p the incidence of aberrantmetaphases in blood cultures is very low.'9Results in fetal lymphocytes are very different;the percentage of cells with the extra chro-mosome was 1%, 3%, 5%, and 100%.357

Clinical diagnosis and investigation of skinfibroblasts with the presence of85% tetrasomiccells were done after the proband's first year in

case 1. Aneuploid cells in cultured fibroblastsare initially present in a high percentage. Afterseveral in vitro passages of cultured skin fibro-blasts or other tissue cells, the isochromosomecan be lost, as is shown by our case 2. Thesame observation has been made by some au-thors.'-" It is possible that i(12p) fibroblastshave a slower growth than diploid cells.

In cases with the typical symptoms of Pallis-ter-Killian syndrome skin biopsy should berepeated if cell growth is poor in the first cul-tures. No correlation between the proportion oftetrasomic cells in different tissues investigatedand the severity of the condition is known sofar.

We would like to thank Mrs Karin Lehmann for in situ hy-bridisation studies.

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2 Horneff G, Majewski F, Hildebrand B, Voit T, Lenard HG.Pallister-Killian syndrome in older children and ad-olescents. Pediatr Neurol 1993;9:213-5.

3 Gilgenkrantz S, Droulle P, Schweitzer M, et al. Mosaictetrasomy 12p. Clin Genet 1985;28:495-502.

4 Sharland M, Hill L, Patel R, Patton M. Pallister-Killiansyndrome diagnosed by chorionic villus sampling. PrenatDiagn 1991;11:477-9.

5 Shivashankar L, Whitney E, Colmorgen G, et al. Prenataldiagnosis of tetrasomy 47,XY,+i (12p) confirmed by insitu hybridization. Prenat Diagn 1988;8:85-91.

6 Soukup S, Neidich K. Prenatal diagnosis of Pallister-Killiansyndrome. Am J Med Genet 1990;35:526-8.

7 Tejada MI, Uribarren A, Briones P, Vilaseca MA. A furtherprenatal diagnosis of mosaic tetrasomy 12p (Pallister-Killian syndrome). Prenat Diagn 1992;12:529-34.

8 Bresson JL, Arbez-Gindre F, Peltie J, Gouget A. Pallister-Killian mosaic tetrasomy 12p syndrome. Another pre-natally diagnosed case. Prenat Diagn 1991;11:271-5.

9 Wenger SL, Steele MW, Yu W-D. Risk effect of maternalage in Pallister i(l2p) syndrome. Clin Genet 1988;34:181-4.

10 Peltomaki P, Knuutila S, Ritvanen A, Kaitila I, de la ChapelleA. Pallister-Killian syndrome: cytogenetic and molecularstudies. Clin Genet 1987;31:399-405.

11 Thornburg Reeser SL, Wenger SL. Failure of PHA-stim-ulated i(12p) lymphocytes to divide in Pallister-Killiansyndrome. Am J7 Med Genet 1992;42:815-9.

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