Parkinson's disease (PD) is a neurodegenerative disorder that may sometimes be caused by deleterious genetic variants. Among them, RAB39B polymorphisms are known as rare causes of early-onset PD associated with intellectual disability (Waisman's syndrome). Here we describe a 45-year-old white male affected by developmental delay, childhood onset intellectual disability, epilepsy, and PD who was treated with subthalamic deep brain stimulation and subcutaneous L-DOPA infusion. Next Generation Sequencing analysis revealed a currently unknown pathogenic hemizygous sequence variant c.463C>T (NM_171998.4) in the RAB39B gene, confirmed also in the proband's mother, affected by late-onset PD. This report expands the number of described RAB39B mutations in individuals with early- and late-onset, X-linked PD.
