Description:Our study identified 23 unique variants in PSMC5, which encodes the AAA-ATPase proteasome subunit PSMC5/Rpt6, causing syndromic Neurodevelopmental Disorder (NDD) in 38 unrelated individuals. PSMC5 loss-of-function resulted in abnormal protein aggregation, profoundly affecting innate immune signaling, mitophagy rate, and lipid metabolism in affected individuals’ samples. These findings deepen our understanding of the molecular mechanisms underlying neurodevelopmental proteasomopathies and link these disorders with neurodegenerative disease research.