The face of Joubert syndrome: a study of dysmorphology and anthropometry

Joubert syndrome (JS) is an autosomal recessive disorder characterized by cerebellar vermis hypoplasia, hypotonia, developmental delay, apnea/hypernea and ophthalmologic abnormalities. Since its description, most attention has focused on hindbrain malformations and the hallmark molar tooth sign (MTS) when visualized on axial magnetic resonance imaging (MRI). Few reports have described a characteristic clinical phenotype of JS and a large cohort of patients has not undergone dysmorphology examinations. In addition, very little is known about other conditions which share some of the clinical and radiological features of JS, including, Arima, Senior-Löken, Dekaban, COACH, and Varadi (OFD VI) syndromes. The purpose of this study was to document the morphologic characteristics of Joubert syndrome based upon detailed dysmorphology and anthropometric examinations in a large cohort of JS individuals to determine whether JS is associated with a specific pattern of malformation. Dysmorphology findings included long face, frontal prominence, bitemporal narrowing, ptosis, prominent nasal bridge and tip, prognathism, eyebrow abnormalities, trapezoid shaped mouth, lower lip eversion, and thick ear lobes. Anthropometric analyses showed several significant differences in measurements including bizygomatic, frontal, nasal, and mandibular dimensions. When compared to controls, younger JS patients had significantly increased facial widths whereas older patients had longer mandibular arc lengths. These data indicate that JS lacks a clear, specific recognizable pattern of malformation, despite being associated with several dysmorphic facial characteristics and distinct anthropometric facial patterns, which change with age. Variability and overlap of features in JS and other hindbrain syndromes makes clinical diagnosis difficult and probably reflects genetic heterogeneity within the cohort of patients with the MTS.