Microdeletions of 3p21.31 characterized by developmental delay, distinctive features, elevated serum creatine kinase levels, and white matter involvement.

Interstitial deletions of chromosome 3 are rare, and only one patient with a microdeletion of 3p21.31 has been reported to date. We identified two additional cases of patients with microdeletions of 3p21.31. The characteristic clinical features of developmental delay and distinctive facial features (including arched eyebrows, hypertelorism, epicanthus, and micrognathia) were seen both in the previously reported patient and in the two newly identified patients. In these two new cases, additional features, including elevated serum creatine kinase levels and characteristic neuroradiological features with white matter involvement, were seen. These features had not been described in the previous case in which the patient was examined during infancy, suggesting an age-dependent mechanism. The shortest region of overlap among the three deletions narrowed down the candidate genes that may be responsible for the common neurological features to the bassoon (presynaptic cytomatrix protein) gene (BSN), which has an important function in neuronal synapses. In this study, we confirmed common phenotypic features in the patients with microdeletions of 3p21.31 and identified additional features that have not been reported previously. Because the constellation of such characteristic features is quite unique, clinical manifestations of the patients with microdeletions of 3p21.31 would be clinically recognizable as a contiguous gene deletion syndrome.