Arq Neuropsiquiat r 2002;60(4):1011-1014
A FURTHER CASE OF A PRADER-WILLI SYNDROM E
PHENOTYPE IN A PATIENT WITH ANGELM AN
SYNDROM E M OLECULAR DEFECT
Greice Andreot t i De M olf et t a
1, Temis M aria Felix
2, M ariluce Riegel
2,
Vict or Evangelist a de Faria Ferraz
1, João M ont eiro de Pina Net o
1ABSTRACT - Angelman syndrome (AS) and Prader-Willi syndrome (PWS) are dist inct human neurogenet ic disorders; how ever, a clinical overlap bet w een AS and PWS has been ident ified. We report on a furt her case of a pat ient show ing t he PWS phenot ype w it h t he AS molecular defect . Despit e t he PWS phenot ype, t he DNA m et hylat ion analysis of SNRPN revealed an AS pat t ern. Cyt ogenet ic and FISH analysis show ed norm al chromosomes 15 and microsatellite analysis show ed heterozygous loci inside and outside the 15q11-13 region. The presence of t hese at ypical cases could be more frequent t han previously expect ed and w e reinforce t hat t he DNA met hylat ion analysis is import ant for t he correct diagnosis of severe ment al deficiency, congenit al hypot onia and obesit y.
KEY WORDS: Angelman syndrome, Prader-Willi syndrome, imprint ing defect .
Outro caso de fenótipo da síndrome de Prader-Willi em um paciente com defeito molecular da síndrome de Angelman
RESUM O - A síndrome de Angelman (SA) e a síndrome de Prader-Willi (SPW) são doenças neurogenét icas dist int as; ent ret ant o, já foi observada sobreposição clínica ent re essas duas pat ologias. Descrevemos mais um caso de um pacient e apresent ando o fenót ipo da SPW e exames moleculares compat íveis com a SA. Apesar do fenót ipo da SPW, o t est e da met ilação do DNA no gene SNRPN revelou padrão compat ível com a SA. A análise cit ogenét ica e análise por FISH most raram ambos os cromossomos 15 normais e a análise de polimorfismo de microssat élit e most rou het erozigozidade para marcadores dent ro e fora da região 15q11-13. A presença dest es casos at ípicos pode ser mais freqüent e que o esperado e salient amos que a análise da met ilação do DNA é import ant e para o diagnóst ico corret o de deficiência ment al, hipot onia congênit a e obesidade.
PALAVRAS-CHAVE: síndrome de Angelman, síndrome de Prader-Willi, defeit o no cent ro de imprint ing.
1Genet ics Depart ment , School of M edicine from Ribeirão Pret o, Universit y of São Paulo (USP), Ribeirão Pret o SP, Brazil; 2M edical Genet ics Service, Hospit al de Clinicas de Port o Alegre, Port o Alegre RS, Brazil. This st udy w as support ed by grant s from FAPESP (98/02378-9). Received 9 M arch 2002, received in final form 17 June 2002. Accept ed 25 June 2002.
Dr. Greice Andreot t i De M olf et t a - Depart ament o de Genét ica, Faculdade de M edicina de Ribeirão Pret o USP - Avenida Bandeirant es 3900 - 14049-900 Ribeirão Pret o SP - Brasil. E-mail: gamolf @rge.f mrp.usp.br
Angelman syndrome (AS) and Prader-Willi syn-drome (PWS) are dist inct human neurogenet ic disor-ders involving t he im print ing m echanism at t he 15q11-13 region. The predominant genet ic defect s in PWS are 15q11-13 delet ions of pat ernal origin and mat ernal chromosome 15 uniparent al disomy1,2.
In cont rast , mat ernal delet ions and pat ernal chro-mosome 15 uniparent al disomy are associat ed w it h AS3,4. A small number of pat ient s w it h PWS and AS
w ere found t o have an imprint ing defect . Such an im print ing def ect can be result of an im print ing cent er (IC) mut at ion or occur spont aneously5. M
u-t au-t ions au-t u-t he UBE3A gene account for approximately
5% of AS6,7. How ever, 10-15% of t he AS pat ient s
have an unknow n et iology8.
AS is clinically charact erized by cent ral congenit al hypot onia, severe ment al deficiency, microcephaly w ith occipital flattening, profound speech delay, jerky volunt ary movement s, a happy disposit ion w it h pa-roxysms of laught er and a charact erist ic facial ap-pearance w hich includes a proeminent jaw w ide mo-ut h and midfacial hypoplasia9. PWS is clinically
cha-ract erized by cent ral hypot onia, hyperf agia and obesit y st art ing aft er t he first year of life, delayed neuromot or development al and lat er, ment al defi-ciency, hypogenit alism, hypogonadot rofic hypogo-nadism and some dysmorphisms10.
1012 Arq Neuropsiquiat r 2002;60(4)
molecular diagnosis based on t he analysis of t he dif-ferent ial parent al specific DNA met hylat ion w it hin t he 15q11-13 region w as compat ible w it h AS.
CASE
The pat ient (Fig 1), an adopt ed child at t he first days of life, w as born t o non-consanguineous and presumed healt hy biological parent s. Informed consent for publi-cat ion w as obt ained from t he adopt ed parent s. Aft er a normal pregnancy t he pat ient w as delivered by caesarian section at full term, w ith a birth w eight of 2950 g (betw een 50-75 cent ile). He present ed w it h neonat al hypot onia but feeding problems w ere not not ed in t he new born period. His development al progress w as delayed. He w alked at 2 years and did not develop any speech unt il 4 years; now he is able t o speak some w ords. He now at t ends a school for children w it h severe learning difficult ies. At t he age of 1 year and 6 mont hs he had one episode of seizures and has been on carbamazepine w it h good cont rol. He had an abnormal EEG and a normal M RI. Aft er t he molecular result a sleep EEG w as performed and show ed t he t ypical slow w ave burst s.
When he w as examined at t he age of 6 years and 4 mont hs his head circumference w as 51.7 cm (50t h cent ile), height 115 cm (bet w een 25-50 cent ile) and w eight 35000 g (above t he 97 cent ile).
The cyt ogenet ic analysis w it h GTG-banding revealed a normal 46,XY karyot ype. Fluorescence in sit u hybridisat ion (FISH) using probes for SNRPN and D15S21 loci (Vysis), w hich map inside t he chromosomal region 15q11-13 and a cont rol probe for t he PM L locus (Vysis) w hich maps t o 15q22, a commom large delet ion of 15q11-13 could be excluded (Fig 2). M et hylat ion analysis at t he SNRPN exon 1 carried out by Sout hern blot analysis revealed an
ab-Fig 2. A) FISH analysis show ing normal pat t ern by bot h chromosomes 15; B) Sout hern blot analysis using t he SNRPN exon 1 probe and genomic DNA digest ed w it h XbaI and Not I. Lane 1: normal cont rol, Lane 2: AS cont rol, Lane 3: PWS cont rol, Lane 4: pat ient ; C) Pat ient microsat ellit es analysis. Lane 1: D15S113, Lane 2: D15S11, Lane 3: GABRB3, Lane 4: D15S123, Lane 5: D15S125, Lane 6: D15S131, Lane 7: FEZ.
Fig 1. Patient at the age of 6 years and 4 months. (photo published w it h parent s consent ).
normal met hylat ion pat t ern w it h t he presence of a 0.9kb pat ernal band and t he absence of t he 4.2kb mat ernal band (Fig 2). M icrosat ellit es analysis of t he pat ient show ed t he presence of t w o bands using markers for t he 15q11-13 region and m arkers w hich m ap out side t he 15q11-13 region (Fig 2). DNA of t he parent s could not be st udied because t he child is adopt ed. Quant it at ive Sout hern blot analysis for t he IC region show ed a normal dosage in t he pat ient ’ s DNA and t heref ore an IC delet ion could be excluded (dat a not show n).
DISCUSSION
To our know ledge, 11 phenot ypically at ypical AS pat ient s have been report ed11-15. Three pat ient s11-13
Arq Neuropsiquiat r 2002;60(4) 1013
GTG banding t echnique revelead a delet ion in t he 15q11-13 region in t w o of t hese cases. The t hird one had a pat ernal UPD(15) due a 45,XY,t (15q15q). Anot her at ypical AS pat ient14 show ed early onset of
obesit y, muscular hypot onia and ment al deficiency leading t o t he clinical suspicion of SPW. This pat ient had a pat ernal UPD(15) case due a mosaic 47,XX, + mar/48,XX,+ 2mar. In addit ion, seven AS pat ient s15
first suspect ed t o have PWS show ed early onset of obesit y, muscular hypot onia and ment al deficiency. All t hese pat ient s w ere found t o have an imprint ing defect w it h no det ect able IC delet ion.
Our pat ient is quit e similar t o t he seven pat ient s report ed by Gillessen-Kaesbach et al.15. He lacks t he
major signs of AS including movement or balance disorder, inappropriat e happiness and most of t he associat ed clinical feat ures (Table 1). The main PWS typical features in our patient are neonatal hypotonia and hyperfagia w it h obesit y. Alt hough init ially PWS w as suspect ed, a m olecular diagnosis of AS w as made by met hylat ion analysis, w hich det ect s PWS
and AS in t he same t est . Unfort unat ely w e w ere not able t o define t he exact genet ic cause of AS in t his pat ient because t he parent al DNA samples w ere not avaiable. We could only rule out t he presence of a commom large delet ion of t he 15q11-13 as w ell as an IC delet ion, but w ere not able t o det ermine if t he pat ient has a pat ernal UPD or an imprint ing defect . How ever, t he fact t hat our pat ient shares exact ly t he same development al and clinical hist ories show ed w it h t he seven imprint ing defect AS pat ient s w ho display a “ PWS-like” phenot ype15 make us t o believe
t hat our pat ient has an IC molecular defect . Indeed, our pat ient has a normal karyot ype also show n by all t he IC molecular defect pat ient s w hile t he AS in patients w ith a cytogenetical abnormality w as caused by a 15q11-13 delet ion or by pat ernal UPD(15). Ano-t her facAno-t or reinforcing Ano-t he presence of a imprinAno-t ing defect in t his pat ient is t hat he is het erozygous by t he microsat ellit e analysis at t he 15q11-13 region and out side t he 15q11-13 region. Alt hought t his do not allow us t o definit ely rule out t he possibilit y of pat ernal het erodisomy, w e should consider t hat t he
Table1. Clinical f eat ures of Angelman syndrome in t he pat ient on t he present report .
Clinical Charact erist ics +
-Consist ent (100%)
Development al delay, funct ionally severe X
Speech impairment X
M ovement or balance disorder, usually at axia of gait X
Happy behavior X
Frequent (more t han 80%)
Delayed grow t h in head circunference X
Seizures X
Charact erist ic EEG X
Associat ed (20 - 80%)
Flat occiput X
Occipit al groove X
Prot uding t ongue X
Tongue t hrust ing; suck/sw allow ing disorders X
Feeding problems during infancy X
Prognat ia X
Wide mout h, w ide-spaced t eet h X
Frequent drooling X
Excessive chew ing/mout hing behaviors X
St rabismus X
Hypopigment ed skin X
Hyperat ive low er limb deep t endon reflexes X
Uplift ed, flexed arm posit ion X
Incresead sensit ivit y t o heat X
Sleep dist urbance X
At t ract ion t o/fascinat ion w it h w at er X
1014 Arq Neuropsiquiat r 2002;60(4)
majorit y of AS uniparent al disomy cases are pat er-nal isodisomy inst ead of pat erer-nal het erodisomy.
We describe an addit ional case w it h overlapping features of AS and PWS, suggesting that the presence of t hese at yp ical could b e m ore f req uent t han p r evi o u sl y exp ect ed . W i t h r eg ar d t o g en et i c co u n sellin g , clin ician s sh o u ld b e aw are o f t h e exist ence of t his form of at ypical AS. It is import ant t hat new cases be ident if ied as it m ight help t o explain how t he imprint ing mechanism w orks w it hin t he 15q11-13 region. We w ould like t o reinforce t hat t he analysis of t he DNA m et hylat ion w it hin t he 15q11-13 region is an import ant t ool for t he correct diagnosis among children w ho present s w it h severe ment al deficiency, congenit al hypot onia and obesit y.
Acknowledgements - We w ish t o t hank Dr Gabriele Gillessen-Kaesbach and Dr Karin Buit ing f rom Essen, Germany, for t he IC quant it at ive Sout hern blot analysis as w ell as for t heir helpful suggest ions on t he manuscript .
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