Bibliographie

1. G. MOUTHEMY, M. KHOURY, M. DOCO-FENZY, M. ADAFER and C. LAJARRIGE, A case of Angelman syndrome in the first year of life.

The diagnosis of Angelman syndrome has seldom been made in infancy because the typical craniofacial dysmorphism and the typical outbursts of unprovoked laughter are not fully developed before the second and third year of life. Other features such as mental retardation or absence of language, though invariably present, are less obvious in the first year of life. We describe three children in whom consecutive electroencephalographic (EEG) studies show very large amplitude slow activity at 2-3/s, often rhythmic, usually occurring in prolonged runs and often more prominent posteriorly, sometimes with spikes or sharp-wave activity, and invariably associated with a diffuse rhythmic activity at 4-6/ s of 200 microvolts. The changes were present as early as six months of life. They preceded development of seizure and occurred much earlier than the craniofacial dysmorphology. It is concluded that methodical use of EEG in the elucidation of children with developmental disorder and knowledge of the characteristic EEG picture may help to identify patients with Angelman syndrome at an early age and before the clinical features become obvious.

Uniparental disomy (UPD) is often the result of an aneuploid event masquerading under the features of diploidy. As such, it may never be recognized, being at 2 opposite phenotypic poles, harmless to the bearer, or, if harmful, eventually responsible for uncharacteristic although perhaps serious conditions. UPD can also be associated with problems such as recessiveness or mosaicism. This article considers the chances of unmasking UPD, in the course of CVS or AC prenatal diagnosis, by reviewing the main cytogenetic signals and major familial or personal antecedents raising its suspicion. Once suspected, the lead toward UPD may or may not be followed through appropriate molecular studies. UPD for either maternal or paternal chromosomes 13, 21 and 22 may not have consistent, common deleterious effects, while other identified UPD's are too rare to call. Unconditionally, main, consistent or near consistent damages to the phenotype have been traced to specific chromosome pairs such as 15 mat (Prader-Willi syndrome), 15 pat (Angelman syndrome), 11 pat (Wiedemann-Beck with syndrome), 14 mat and pat (multiple cogenital and developmental anomalies [MCDA]-several rather constant) and 7 mat (Russel-Silver [RS] and Growth-failure [GF]). The above problems all stem from an alteration of the normal, developmentally important genomic imprinting processes and most of them may recognize several etiopathogenic paths, other than UPD, none of which abides by straight Mendelian rules. In this very area, therefore, a new, non-traditional type of inheritance is confronting genetic counselling. In this paper, for want of appropriate semantic language, the neologism "likon" (or "laikon") is coined to make reference to the hemizygously expressed sequences of the genomic parts imprinted in the somatic tissues. Broadening the definition, the word is then applied to the 4 possible epigenotypes of imprinted domains, which depend on the parental sex-of-origin: germinally "resting" (R), or "acting" (A), to be made somatically silent, that is to say "unexpressed" (U), or transcribed and "expressed" (E), thus abbreviated as EA, ER, UA and UR. Entire pedigrees may then be analyzed accordingly in health and in disease. Examples are presented herewith.

With improvements in culturing and banding techniques, amniotic fluid studies now achieve a level of resolution at which the Prader-Willi syndrome (PWS) and Angelman syndrome (AS) region may be questioned. Chromosome 15 heteromorphisms, detected with Q- and R-banding and used in conjunction with PWS/AS region-specific probes, can confirm a chromosome deletion and establish origin to predict the clinical outcome. We report four de novo cases of an abnormal-appearing chromosome 15 in amniotic fluid samples referred for advanced maternal age or a history of a previous chromosomally abnormal child. The chromosomes were characterized using G-, Q-, and R-banding, as well as isotopic and fluorescent in situ hybridization of DNA probes specific for the proximal chromosome 15 long arm. In two cases, one chromosome 15 homolog showed a consistent deletion of the ONCOR PWS/AS region A and B. In the other two cases, one of which involved an inversion with one breakpoint in the PWS/AS region, all of the proximal chromosome 15 long arm DNA probes used in the in situ hybridization were present on both homologs. Clinical follow-up was not available on these samples, as in all cases the parents chose to terminate the pregnancies. These cases demonstrate the ability to prenatally diagnose chromosome 15 abnormalities associated with PWS/AS. In addition, they highlight the need for a better understanding of this region for accurate prenatal diagnosis.

We report two patients who were less than two years old that were diagnosed as having Angelman syndrome. Cytogenetic confirmation of the disease was performed. We emphasize clinical and electroencephalographic features in infants that allow an early diagnosis of this syndrome and allow for prompt genetic counseling.

The diagnosis of Angelman syndrome (AS) has seldom been made in infants because the previously described characteristic manifestations usually are not apparent until after age 2 years. We describe 4 AS patients, one of whom has oculocutaneous albinism, who were less than 2 years old when first evaluated. All 4 have deletions of the region q11.2-q13 of chromosome 15. In the 3 cases in which parents were available for study the deleted chromosome 15 was maternally derived, as determined by cytological markers. All of the patients presented with severe to profound global developmental delay and postnatal-onset microcephaly; they had seizures, hypotonia, hyperreflexia, and hyperkinesis. All were hypopigmented as compared to their relatives. Each had eye abnormalities; all had choroidal pigment hypoplasia. None were initially described as having an abnormal appearance. We believe that AS is far more common than previously thought and present these 4 children to emphasize the manifestations that may be helpful in making the diagnosis in the young patient. We also emphasize the hypopigmentation that patients with AS frequently have, including what we think is the first reported case of albinism and AS.

Angelman syndrome usually has been considered to be rare and sporadic. However, recent reports suggest a sibling recurrence risk of just under 25 per cent, so early diagnosis is very important. The authors report Angelman syndrome in a child of seven months. The early features of this syndrome (jerky movements, EEG characteristics, chromosomal abnormalities in half the cases) should make it possible to diagnose or suspect the syndrome in the first year of life.

The authors report an 11-month-old patient with the clinical features of Angelman syndrome and a 15q11 x 2-12 chromosomal deletion, thus demonstrating that the clinical features may be present in infancy and so allow early diagnosis. The features included pronounced postnatal growth failure, delayed dentition and ossification of growth centers. Low amniotic fluid alpha-fetoprotein was noted at 16 weeks of gestation. Head MRI showed only generalized atrophy. Some affected patients have a genetic marker similar to the chromosomal deletion associated with Prader-Willi syndrome. The importance of awareness of the clinical symptoms of Angelman syndrome is discussed.