ReNU syndrome is a very rare genetic disorder caused by changes in the RNU4-2 gene, which is important for RNA splicing. Disorders in this gene lead to severe impairments in brain development.

Typical symptoms include pronounced hypotonia, significant developmental delays, little or no speech, delayed or absent walking and growth disorders. Epileptic seizures, characteristic facial features and brain changes such as hydrocephalus or reduced development of the corpus callosum are also common.

Diagnosis is difficult as changes in the RNU4-2 gene are often not detected in conventional genetic analyses and special tests are required.