Alexis D. Levine1 and Wendy K. Chung2 1New York Medical College, Valhalla, New York 10595, USA; 2Columbia University, New York, New York 10032, USA Corresponding author: alevine220gmail.com

PPP2 syndrome type R5D, or Jordan's syndrome, is a neurodevelopmental disorder caused by pathogenic missense variants in PPP2R5D, a β-subunit of the Protein Phosphatase 2A (PP2A). The condition is characterized by global developmental delays, seizures, macrocephaly, ophthalmological abnormalities, hypotonia, attention disorder, social and sensory challenges often associated with autism, disordered sleep, and feeding difficulties. Among affected individuals, there is a broad spectrum of severity, and each person only has a subset of all associated symptoms. Some, but not all, of the clinical variability is due to differences in the PPP2R5D genotype. These suggested clinical care guidelines for the evaluation and treatment of individuals with PPP2 syndrome type R5D are based on data from 100 individuals reported in the literature and from an ongoing natural history study. As more data are available, particularly for adults and regarding treatment response, we anticipate that revisions to these guidelines will be made.