Novel mutation in ARX associated with early hand preference and a mild phenotype.

The authors report detailed clinical and developmental assessment of 3 brothers who were found to carry a novel mutation in the ARX gene associated with a relatively mild phenotype of static global developmental delay and early hand preference. The decision of when to initiate specialized genetic testing for patients with apparently isolated developmental delay remains controversial, and this report of 3 brothers who presented with early hand preference and transient contralateral weakness may assist clinicians in prioritizing investigations in patients with a similar presentation.