Le syndrome de Prader-Willi (SPW) est une maladie génétique d’empreinte aboutissant à l’absence d’expression des gènes de la région du chromosome 15q11.q13 d’origine paternelle. Sa prévalence est estimée entre 1/10 000 à 1/25 000 naissances. Il se manifeste initialement par une hypotonie néonatale associée à des troubles de l’oralité et un hypogonadisme. Dans un second temps, on observe un retard de développement, des troubles du comportement avec hyperphagie et obésité importante. Le diagnostic, évoqué sur des critères cliniques, est confirmé par les analyses génétiques. Il est possible en anténatal, évoqué devant un hydramnios avec fœtus petit pour l’âge gestationnel, immobilisme fœtal et malposition des doigts. Nous rapportons une série de 5 nouveau-nés présentant un SPW. L’objectif principal était d’étudier les signes d’appel anténatals et périnatals du SPW. La prévalence dans notre population est de 1/7937 naissances. Le SPW avait été évoqué sur des critères cliniques : hypotonie sévère, troubles de l’oralité, dysmorphie et anomalies des organes génitaux. Quatre enfants étaient nés à terme avec un poids de naissance proche du 10^e percentile pour 2 enfants, inférieur au 3^e percentile pour 2 avec un périmètre crânien normal. Quatre enfants présentaient une malposition des doigts. Les analyses génétiques avaient montré une délétion sur le chromosome 15 paternel pour 3 enfants, une unidisomie maternelle pour 2 enfants. Le SPW doit être recherché devant une hypotonie néonatale sévère, ce d’autant que s’y associent dysmorphie, hypogonadisme, malposition des doigts et histoire anténatale évocatrice. Le diagnostic précoce, voire anténatal, permet une meilleure prise en charge pluridisciplinaire de l’enfant et de sa famille.

Prader-Willi syndrome (PWS) is a fingerprint disease caused by the loss of paternally inherited chromosome 15q11.2–q13. In several populations studied, prevalence is estimated to be from 1/10,000 to 1/25,000 births. The disease initially manifests by neonatal hypotonia associated with orality disorders. Secondly, hyperphagia appears with significant obesity and hypogonadism. Motor milestones and language development are delayed, and all individuals have variable degrees of cognitive disability during childhood. Frequently, the most prominent features do not become evident until the later childhood stage, which can lead to underdiagnosis or late diagnosis in early childhood. Because of the long-term implications of this syndrome, it is important to recognize its features as soon as possible so that early counseling of parents and the affected child is possible. The diagnosis is suspected on clinical grounds and confirmed by genetic analysis. Prenatal diagnosis is possible and can be considered in polyhydramnios, decreased fetal active movements, malpresentation, oddly positioned hands and feet, and abnormal fetal heart rhythm. Since PWS can also lead to complications in both pregnancy and labor, proper prenatal diagnosis can also help optimize perinatal care for affected children. We report a series of five newborns for whom PWS was diagnosed in the neonatal period over 6 years. During this period, no prenatal signs of PWS were detected. The incidence in our population was 1/7937 births. The disease was diagnosed on clinical criteria: severe hypotonia, failure to thrive with poor sucking, and dysmorphic and abnormalities of the genitalia. Polyhydramnios was observed in only one case. The delivery was normal for only one patient. All except one were term newborns. There were three males and two females. We noted abnormal fetal heart rate for 80 % of the patients. The birth weight was close to the 10th percentile for two patients, less than the 3rd percentile for two others. All individuals had eutrophic cranial perimeter and four presented peculiar position of fingers. Genetic analyses found a deletion of the paternal chromosome 15 in three patients (60 %) and maternal uniparental disomy for the two others (40 %). The distribution by sex, weight, cranial perimeter, and mutations are those reported in the literature. PWS should be sought in cases of severe neonatal hypotonia, most particularly if it combines dysmorphism, hypogonadism, malposition of the fingers, and suggestive prenatal history. An early diagnosis provides better multidisciplinary care for the patient and family. We have no explanation for the higher incidence of the disease than in the general population. It is possible that this incidence is only fortuitous, but further studies would help to identify potential risk factors for the disease.