Objective studies of the face of Noonan, Cardio-facio-cutaneous, and Costello syndromes: A comparison of three disorders of the Ras/MAPK signaling pathway

Noonan, Cardio‐facio‐cutaneous, and Costello syndromes are disorders of the Ras/MAPK pathway that share many clinical features. This observational and anthropometric study was conducted to describe the key facial features of each syndrome in order to improve discrimination between the three conditions, particularly in young children where diagnosis is most challenging. Direct measurement of the head and face was used to enhance diagnostic accuracy, and identify the most unusual or specific dimensions. The Noonan syndrome cohort included 123 individuals, aged 6 months to 41 years. There were 20 children and adolescents with Cardio‐facio‐cutaneous syndrome, and 28 individuals with Costello syndrome, aged 1–32 years. The facial phenotypes of these syndromes, particularly Noonan syndrome, are well‐described but objective data have not been published in peer‐reviewed literature. In this study, subjective observations, in the main, were validated by anthropometry with one exception. In individuals with Costello syndrome, mouth width was normal, thus the impression of wide mouth is likely due to full lips or the mouth being viewed in relation to a narrow lower face. When the three conditions were compared objectively, syndrome‐specific pattern profiles showed high concordance in early life. At older ages, Cardio‐facio‐cutaneous syndrome was distinguished by increased width of the mid/lower face, and reduced growth of maxillary and mandibular dimensions was noted in both Noonan and Costello syndromes. Despite substantial similarities in face shape in older individuals with these two conditions, bulbous nasal tip, full lips, and an apparently wide mouth in those with Costello Syndrome facilitate discrimination from Noonan syndrome. © 2016 Wiley Periodicals, Inc.