Two patients with EP300 mutations and facial dysmorphism different from the classic Rubinstein-Taybi syndrome

Rubinstein-Taybi syndrome (RTS) is characterized by mental retardation, broad thumbs and great toes and a recognizable craniofacial phenotype. Causative mutations have been described in the CREBBP and EP300 genes. Here we present a 19-year-old woman and an unrelated 3-year-old boy, both with broad thumbs and halluces, but with facial aspects distinct from those of typical RTS. The woman had a marked learning disability, but no mental retardation. We identified a de novo c.7100delC mutation in EP300 (which predicts p.P2366RfsX35) in the woman and an apparently de novo c.638delG mutation in the boy, which predicts p.G213EfsX6. Mutations in EP300 are a known but rare cause of RTS. Only five ot…