PLA2G6 and pantothenate kinase-associated neurodegeneration: The two core syndromes, accounting for most cases, are the neuroaxonal dystrophies pantothenate kinase-associated neurodegeneration (PKAN, formerly known as Hallervorden-Spatz disease), currently classified as NBIA type 1 and PLA2G6-associated neurodegeneration (PLAN), classified as NBIA type 2.