Researchers at the Icahn School of Medicine at Mount Sinai in New York have identified and described a previously unknown recessive neurodevelopmental disorder (NDD) that appears to be the most prevalent ever discovered. The condition is caused by changes in a small noncoding gene called RNU2-2. It is estimated to affect thousands of individuals in the United States and account for about 10% of all recessive NDD cases with a known genetic cause.

The work was done in collaboration with U.S. collaborators in the Undiagnosed Diseases Network led by colleagues at Stanford University and international collaborators in the United Kingdom, the Netherlands, Belgium, and Italy. The findings, published in the March 30 issue of Nature Genetics, provide long-awaited answers for many families and may inform future drug development.

The team found that the disorder is caused by a near-complete absence of a molecule called U2-2 RNA, which is produced by the RNU2-2 gene. Children with the condition typically inherit one altered copy of the gene from each parent, although sometimes changes arise spontaneously by genetic mutation. While the parents are unaffected, the combined effect on both copies of the gene in their children leads to disrupted brain development in their child.