We recently showed that mutations in the snRNA genes RNU4-2 and RNU2-2 are prevalent causes of dominant neurodevelopmental disorders (NDDs). Here, by genetic association, we demonstrate the existence of a recessive form of RNU2-2 syndrome. We inferred a log Bayes factor for a recessive model of association of 18.2. Conditional on that model, 17 rare variants had a posterior probability of pathogenicity >0.8. This conservative threshold identified 18 probands and 5 affected siblings, each carryin