Williams Syndrome

Williams Syndrome

Williams syndrome is characterised by supravalvar aortic stenosis, elfin facies with low nasal bridge and hypercalcemia with hypercalciuria. Learning disability is often associated. Peripheral pulmonary stenosis is also an association. In supravalvar aortic stenosis, the right upper limb blood pressure can be more than that in left upper limb (anisopsphygmia) because the jet is directed towards the brachiocephalic artery. This is known as Coanda effect.

Coanda effect is the tendency of a jet stream to adhere to a wall, usually causing higher blood pressure in the right upper limb in supravalvar aortic stenosis. In a series of 56 patients, 48 had unequal blood pressure in the upper extrermities. The average difference was 18 mm Hg. Although 11 of 20 patients with valvar aortic stenosis had some asymmetry, the average difference was only 3.5 mm Hg [1].

Williams syndrome is due to a microdeletion on chromosome 7, which can be confirmed by fluorescence-in-situ hybridization (FISH) or multiplex ligation probe amplification (MLPA). A series of 11 patients have been reported by Subapriya Kandasamy and associates [2]. Cardiac anomalies were detected in 5 out 9 patients who underwent echocardiography. The defects noted were aortic stenosis, pulmonary stenosis, ventricular septal defect and mitral valve prolapse.

References

1. J W French, W G Guntheroth. An Explanation of Asymmetric Upper Extremity Blood Pressures in Supravalvular Aortic Stenosis: The Coanda Effect. Circulation. 1970 Jul;42(1):31-6.
2. Subapriya Kandasamy, Deepti Saxena, Yougal Kishore, Shubha R Phadke. Williams Syndrome: A Case Series. Indian Pediatr. 2014 May;51(5):411-2.