Rubinstein-Taybi syndrome: objective evaluation of craniofacial structure

Rubinstein-Taybi syndrome (RTS) is a rare multiple congenital anomaly syndrome comprising mental and growth retardation, broad thumbs and great toes, and an unusual face. The classical facial appearance is well-established, striking and easy to recognize. It includes downslant of the palpebral fissures, epicanthic folds, ptosis, strabismus, highly arched palate, simple ears and a small mouth. The nose is distinctive with a beaked appearance, broad fleshy bridge, deviated septum and short low columella. Previous studies have documented considerable change in this facial phenotype with time. In this study, we evaluated 31 individuals with RTS from Great Britain and The Netherlands. They range in age from 1 to 39 years. Detailed craniofacial measurements were obtained on each subject and composite pattern profiles were compiled. There was remarkable concordance of patterns at all ages from infancy to adulthood. Microcephaly was present consistently. The head was relatively round with head width equal to head length. There was narrowness at the skull base with relative broadening of the minimal frontal diameter and lower facial width. The mouth was small and ears were broad and short. Eyes were wide-spaced in comparison to upper facial width and head circumference. The child under 4 years demonstrated some differences. Width and depth of the upper face exceeded that of the lower face, whereas with increasing age, mandibular dimensions were closer to normal than their maxillary counterparts. Despite these differences, the similarity of the profiles of all age groups seems to belie the phenotypic changes that can be appreciated subjectively. This suggests that major components of the change in appearance are those which have not been assessed in this study, such as palpebral fissure slant, deviation of the nasal bridge, presence of epicanthal folds or ptosis; or for which norms are not available, for example, beaking of the nose, and low nasal septum.