He was first referred at the age of 9K years (fig 1A) for school difficulties secondary to mild mental retardation (IQ of 50), MCA with ectomorphic habitus (height 147 cm (. P97), weight 25.7 kg (P3) and a normal occipito-frontal circumference of 54.2 cm). He has characteristic dysmorphic features including high forehead, fine hair, telecanthus, antimongoloıd palpebral fissures, large ears, broad and high nasal root with prominent tip, high palate with nasal speech, everted lower lip, long fingers, pectus excavatum, kyphoscoliosis (. 20u), congenital heart defect consisting of a bicuspid aortic valve with mild aortic valve insufficiency without stenosis and a prolapsed mitral valve with a first grade mitral insufficiency. He underwent surgery with good post-surgical haemodynamic results.

He has no symptoms of AD. Brain magnetic resonance imaging (MRI) was normal at the age of 30 months. A high resolution G-banded karyotype was normal 46, XY. At the age of 13 years, he had a height of 170 cm (P97) and was delayed for one school year. Marfan syndrome was suspected but no mutations in the FBN1 gene were detected, and there was no deletion of the ELN gene with the Williams-Beuren syndrome FISH probe Oncor WSCR (Oncor, Gaithersburg, Maryland, USA). Now at the age of 16 years, his height is 184.5 cm (P97) for a weight of 44 kg (, P3)(fig 1B, C). Endocrinological screening showed an increased follicle stimulating hormone (FSH) concentration (24.1 IU/l) with a normal luteinising hormone (LH)(5.2 IU/l) and a testosterone concentration at the lower range (310 ng/dl). Bone age was in accordance with the chronological age. The clinical features are summarised in table 1.