Neurodegeneration with brain iron accumulation (NBIA) is a genetically heterogeneous disorder characterized by progressive iron accumulation in the basal ganglia and other regions of the brain, resulting in extrapyramidal movements, such as parkinsonism and dystonia. Age at onset, severity, and cognitive involvement are variable. NBIA1, or pantothenate kinase-associated neurodegeneration (PKAN), has been classified clinically as 'classic,' 'atypical,' or 'intermediate.' In the classic form, patients present within the first decade of life with rapidly progressing disease and loss of ambulation approximately 15 years later. In the atypical form, patients have onset in the second decade with slow progression and maintain independent ambulation after 15 years. In the intermediate form, patients have early onset and slow progression or later onset and rapid progression. Patients with early onset tend to develop pigmentary retinopathy, whereas those with later onset tend to have speech disorders and psychiatric features. Most patients have the 'eye of the tiger' sign on brain MRI, although that finding is not pathognomonic for PANK2 mutations. [From OMIM]