Prader—Willi syndrome in a child: a clinical case with a multidisciplinary approach

Prader—Willi syndrome (PWS) is a rare genetic disorder classified among imprinting­related conditions and results from the loss of expression of paternally inherited genes in the 15q11­-q13 chromosomal region. The most common mechanism is a de novo paternal deletion of 5—6 Mb in the 15q11-q13 region, observed in approximately 60 % of cases. The prevalence of PWS is approximately 1 in 15,000 to 30,000 live births, irrespective of sex or ethnicity. PWS is a multisystem disorder characterized by a range of age-dependent clinical features. The course of the syndrome is typically divided into two clinical stages: the first is marked by delayed physical development, while the second is associated with hyperphagia and the onset of obesity.Prenatal features include reduced fetal movements (88 %), breech presentation, and preterm birth. Other fetal characteristics include small size for gestational age (65 %) and an increased head-to-abdomen circumference ratio (43 %). Polyhydramnios (34 %) is also observed, likely reflecting impaired coordination of sucking and swallowing, which typically develops after 36 weeks of gestation in healthy fetuses. In the neonatal period, the predominant features include muscular hypotonia, poor sucking reflex, and feeding difficulties. During early childhood, further hallmark features typically emerge, such as short stature, hypogonadism, delayed psychomotor development, and progressive hyperphagia, which — if left unaddressed — leads to severe obesity. Behavioral issues are frequently observed, including obsessive-­compulsive traits, temper outbursts, and compulsive skin picking. Cognitive development usually ranges from mild to moderate intellectual disability.Despite the well­-described clinical picture, the phenotype of PWS can be variable, complicating early diagnosis. This clinical case presents a child with classical but late­recognized manifestations of PWS, highlighting the importance of an interdisciplinary approach and a high index of clinical suspicion among pediatricians, pediatric endocrinologists and geneticists.