RAB23 mutation in a large family from Comoros Islands with Carpenter syndrome

We report here on a RAB23 mutation (c.86dupA) present in the homozygote state in four relatives of Comorian origin with Carpenter syndrome. All children presented with acrocephaly and polysyndactyly. However, intrafamilial variability was observed with variable severity of craniosynostosis ranging from cloverleaf skull to predominant involvement of the metopic ridge. All children also presented with a combination of brachydactyly with agenesis of the middle phalanges, syndactyly, broad thumbs, and postaxial polydactyly (2/4) in the hands, and preaxial polydactyly (3) and syndactyly (4) in the toes. Mental development was normal in all four children but the eldest one presented with impaired motor development as a result of orthopedic complications. Brain imaging showed hydrocephalus in 2/4 and additional features included genu valgum (2/4), abnormal genitalia (3/4), corneal anomaly (2/4), umbilical hernia (1/4), severe cyphoscoliosis (1), patent ductus arteriosus (1/4), and accessory spleen (1). In contrast to previous reports, growth was below average except for one patient and the eldest one became moderately overweight with time. We conclude from the report of this large unique family with four affected children that Carpenter syndrome is a genetically homogenous but a clinically variable condition.