Neonatal hypotonia: don't forget the Prader-Willi syndrome

During the neonatal period the diagnosis of the Prader-Willi syndrome (PWS) is difficult because the syndrome is expressed mainly by severe hypotonia at this age and the typical clinical features of later life are not yet present.

To identify all the PWS clinical markers in severe hypotonic newborns, which could facilitate an early diagnosis of the syndrome.

Twenty-one PWS newborns (14 males and 7 females) with severe hypotonia at birth were evaluated. Paediatricians skilled in syndromology carried out a careful clinical examination. Fluorescent in situ hybridization (FISH) analysis and/or a methylation test was used to confirm the PWS clinical diagnosis.

The clinical diagnosis of PWS was reached at a mean age of 7.4 mo with genetic confirmation at 11 mo of life. In 12 newborns at least 3 craniofacial features were present (57%), suggesting the diagnosis of PWS. Two craniofacial dysmorphic characteristics were described in 6 newborns and only 1 in 3 cases. Cryptorchidism was monolateral in 6 and bilateral in 7 patients; in one newborn both testes were in scrotum. A micropenis was described in one patient and hypoplasia of the labia minora was reported in two females.

Diagnosis by means of dysmorphologic evaluation is difficult in the neonatal period. The presence of severe hypotonia should always induce neonatologists to perform specific genetic tests in order to obtain an early diagnosis of PWS.