Prader-Willi Syndrome: an under-recognized cause of hypotonia?

The “floppy infant” is a well-recognized entity characterized by general­ized hypotonia presenting at birth or in early life. Hypotonia represents a diagnostic challenge because it may be the presentation sign of numerous diseases, as central or peripheral nervous system abnormalities, myopathies, genetic disorders, endocrinopathies, metabolic diseases and acute/chronic illness. Prader-Willi syndrome (PWS) is a complex neurodevelopmental disorder that results from an abnormality in chromosome 15. Diagnosis is often delayed because clinical findings are relatively nonspecific and the dysmorphism is often subtle. We describe three term male newborns admitted in the first day of life for hypotonia and feeding difficulties. Pregnancy and familiar history were unremarkable. Clinical examination revealed marked global hypotonia, few active movements, weak cry, poor suck reflex, micrognathia, cryptorchidism, facial dysmorphic features: almond-shaped eyes with short palpebral fissures, narrow bifrontal diameter and short neck. Laboratory evaluations were normal. Brain ultrasound and magnetic resonance had no alterations. Cardiac and metabolic evaluations were irrelevant. PWS was suspected and genetic evaluation was performed. The methylation analysis specific for PWS confirmed the diagnosis. In the three cases it was observed development milestones delay, with progressive improvement after multidisciplinary approach. At last follow-up visit, all of them walk alone, explore the surrounding environment, understand simple language and say some words. These reports reinforce the idea that PWS should be considered in the presence of newborn hypotonia, and feeding difficulties, even in absence of typical facial features. Detecting PWS at neonatal age is important because it allows early intervention and better management of such infants.