We report two families with seven siblings with de Barsy syndrome. Characteristic features include severe mental retardation, hypermobility with athetoid movements, grimacing, muscular hypotonia, laxity of small joints and brisk deep tendon reflexes, progeroid aspect with cutis laxa, atrophy of skin with hyperpigmentation, isolated depigmentations, reduction of subcutaneous fatty tissue, translucent vein pattern, short stature, frontal bossing in the young child, large prominent ears with dysplastic helices and corneal clouding or cataracts. The syndrome probably has autosomal recessive inheritance.