Herlyn-Werner-Wunderlich and Prader-Willi syndromes: more than a coincidence?

A neonate with a prenatal diagnosis of left renal agenesis was born at 33 weeks gestation. A postnatal abdominal ultrasound confirmed the absence of the left kidney and revealed two non-divergent hemiuteri, consistent with the diagnosis of Herlyn-Werner-Wunderlich syndrome. During admission, significant axial hypotonia was noted, warranting additional investigations. Brain ultrasounds and MRI were normal, as were a preliminary metabolic study and comparative genomic hybridisation array. DNA methylation testing confirmed the diagnosis of Prader-Willi syndrome. The baby was discharged after 70 days, breast feeding and with modest hypotonia improvement.