The PPP2R5D (Protein Phosphatase 2 Regulatory Subunit B’ Delta)-related disorder, also known as Houge–Janssens syndrome 1 (OMIM #616355) or Jordan’s syndrome, is an autosomal, dominant (AD) condition with onset in early childhood characterized by moderate-to-severe developmental delays. This evidence concerns the gene PPP2R5D and Alzheimer disease.