Abstract
BACKGROUND: Prader-Willi Syndrome (PWS) is a multisystemic disorder characterized by dysmorphic facies, hypotonia, developmental delay, cognitive impairment, hypogonadism, and obesity. It is caused by the absence of expression of paternally derived genes on chromosome 15. Here, we report the diagnostic journey of a case with severe neonatal hypotonia. CASE REPORT: A neonatal patient was referred for the prediagnosis of spinal muscular atrophy (SMA). During the SMA Multiplex Ligation-dependent Probe Amplification (MLPA) analysis, a diminished signal of a reference probe on the 15q11.2 was revealed. Later, it was confirmed that she had a deletion confined to 15q11.2-q13.1, with a methylation pattern compatible with PWS. CONCLUSION: Since hypotonia might be the only finding in newborns with PWS, this case was presented to emphasize the importance of a comprehensive approach to such patients.