Williams syndrome (WS) results from the micro deletion of contiguous genes at chromosome 7q11.23 [1].

This genome part includes several genes [2] like ELN (ELastiN), encoding the tissue structural protein elastin [3], and Gtf2i (General Transcription Factor II-I), encoding a multifunctional phosphoprotein with roles in transcription and signal transduction [4]. This results in a multisystem disorder involving the cardiovascular [5], connective tissue and central nervous system. The incidence of typical forms is 1:20,000 people [6]. The clinical description associates a supravalvular aortic stenosis and/or a steno¬sis of the branches of pulmonary arteries, a psychomotor retardation and a facial dysmor¬phism [7,8]. An association with neonatal hypercalcaemia has also been reported [9]. The facial dysmorphism is characterised by an elfin facies syndrome: stellate pattern of the irises [10], broad forehead, periorbital fullness, high and rounded cheeks, pointed chin, flattened nasal bridge and upturned nose, long philtrum and wide and everted lower lip [11]. The most frequent orofacial alteration is malocclusion (94%) [12]. In addition to the psychomotor retardation, these patients have a disharmonious IQ (intelligence quotient) profile and are scoing better in verbal tests [13]; they are hypersocial and have major anxiety [14,15]. They also have musical abilities [16,17]. Cardiovascular abnormalities are common in WS [18]; most of them are arterial stenosis. Forty-five to 75% of WS patients suffer from supravalvular aortic stenosis and/or pulmonary arteries stenosis. Eighty percent of WS patients have cardiac abnormalities (aortic, mitral and/or tricuspid valve abnormalities, ventricular hypertrophy), they also have coronary artery abnormalities [19]. Systemic arteriopathy in other vessels of the body occur in 20% of cases, preferentially affecting the thoracic aorta (which can be associated with renal artery stenosis), but other sites are also possible (neck, limbs abdominal aorta…). Most of the cardiovascular abnormalities are found in the first year of life [11]. They also can suffer from endocrine dysfunction [20,21], pulmonary emphysema [2], ophthalmologic manifestation [22,23] or epilepsy [24].