When Powerhouses Fail and Rust Takes Over: Primary Mitochondrial and Lipid Metabolism Failure with Secondary Iron Accumulation and Lipid Peroxidation in Neurodegeneration with Brain Iron Accumulation

Neurodegeneration with brain iron accumulation (NBIA) comprises a genetically heterogeneous group of rare movement disorders characterized by progressive neurodegeneration and selective basal ganglia iron deposition. Recent discoveries have fundamentally reshaped the understanding of NBIA, indicating that defects in coenzyme A metabolism, mitochondrial bioenergetics, lipid remodeling, autophagy-lysosomal pathways, and ferroptosis precede and promote secondary iron dyshomeostasis rather than resulting from primary abnormalities in iron metabolism. This review integrates recent mechanistic and translational evidence (2020-2026) across both common and underrepresented NBIA subtypes, including pantothenate kinase-associated neurodegeneration, phospholipase A2-associated neurodegeneration, COASY protein-associated neurodegeneration, mitochondrial enoyl-CoA reductase protein-associated neurodegeneration, mitochondrial membrane protein-associated neurodegeneration, β-propeller protein-associated neurodegeneration, fatty acid hydroxylase-associated neurodegeneration, neuroferritinopathy, and mitochondrial DNA-associated forms. Unlike previous reviews, this synthesis consolidates findings from patient-derived induced pluripotent stem cell neuronal and glial models, compartment-specific iron localization, advanced neuroimaging biomarkers, and emerging therapeutic strategies within a unified mechanistic framework. Collectively, the evidence supports a paradigm in which mitochondrial dysfunction and lipid metabolic failure initiate disease progression, whereas iron accumulation amplifies oxidative injury and lipid peroxidation, thereby increasing ferroptotic cell death and neuronal degeneration, providing an updated foundation for biomarker discovery, mechanistically informed therapeutic development, and precision medicine approaches in NBIA.