Neurodegeneration with brain iron accumulation.

Neurodegenerative disorders with brain iron accumulation (NBIA) are a clinically and genetically heterogeneous group of conditions in which there is neurodegeneration accompanied by elevated levels of brain iron. NBIA is frequently of genetic etiology, but may be secondary to an acquired systemic or neurological disease. Mutations in the ferritin light chain cause an adult-onset autosomal-dominant choreiform movement disorder termed neuroferritinopathy. Homozygous mutations in the ceruloplasmin gene cause aceruloplasminemia, which is characterized by the triad of diabetes, retinopathy, and a neurological disorder in mid adulthood. Mutations in pantothenate kinase 2 (PANK2) and phospholipase A2 (PLA2G6) cause recessive, childhood-onset extrapyramidal disorders termed pantothenate kinase-associated neurodegeneration (PKAN) and infantile neuroaxonal dystrophy (INAD), respectively. There is considerable phenotypic overlap between these conditions. The most useful investigation in suspected NBIA is brain magnetic resonance imaging, which can identify pathological iron deposition and distinguish between genotypes. Iron depletion therapy has been demonstrated to be successful in aceruloplasminemia, but not neuroferritinopathy, PKAN, or INAD. The presentation of NBIA overlaps with the more common adult movement disorders and pediatric neurometabolic conditions, and a high index of suspicion is required to make a correct diagnosis.