RSK2 gene mutations in Coffin–Lowry syndrome with drop episodes

Coffin–Lowry syndrome is an X-linked mental retardation disorder with dysmorphism caused by mutation of the ribosomal S6 kinase (RSK2) gene. Coffin–Lowry syndrome patients can experience unusual drop episodes whereby an abrupt loss of muscle tone and falling down can be induced by sudden, unexpected tactile or auditory stimuli. We detected a C913T (R305X) mutation in a female Coffin–Lowry syndrome patient with drop episodes. All mutations in our patient and those previously reported in patients with drop episodes result in premature truncation of the RSK2 protein in the N-terminal kinase domain or upstream of this domain