PRADER-WILLI-LIKE PHENOTYPE IN FRAGILE-X SYNDROME

A 3-year-old boy was referred to the pediatric department because of u nexplained extreme obesity. Height and occipitofrontal circumference w ere just above the 90th centile. Endocrine studies failed to show any significant abnormality. Motor and speech development were generally d elayed. On clinical-cytogenetic-molecular grounds, Prader-Willi syndro me was excluded. Fragile X syndrome was diagnosed by the presence of t he classical FMR-1 mutation and confirmed by cytogenetic studies, reve aling 20% fragile X positive cells. We compare the clinical features i n the present patient with the nine reported patients with fra(X) synd rome and extreme obesity. In pathogenesis, hypothalamic dysregulation is hypothesized. In differential diagnosis of Prader-Willi syndrome, f ragile X has to be considered, especially when laboratory workup for P rader-Willi syndrome is negative. Clinical behavior can be of help.