Newly characterized forms of neurodegeneration with brain iron accumulation.

Neurodegeneration with brain iron accumulation (NBIA) comprises a group of brain iron deposition syndromes that lead to mixed extrapyramidal features and progressive dementia. Historically, there has not been a clearly identifiable molecular cause for many patients with clinical and radiologic features of NBIA. Recent discoveries have shown that mutations in C19orf12 or WDR45 can lead to NBIA. C19orf12 mutations are inherited in an autosomal recessive manner, and lead to a syndrome similar to that caused by mutations in PANK2 or PLA2G6. In contrast, WDR45 mutations lead to a distinct form of NBIA characterized by spasticity and intellectual disability in childhood followed by the subacute onset of dystonia-parkinsonism in adulthood. WDR45 mutations act in an X-linked dominant manner. Although the function of C19orf12 is largely unknown, WDR45 plays a key role in autophagy. Each of these new forms of NBIA thus leads to a distinct clinical syndrome, and together they implicate new cellular pathways in the pathogenesis of these disorders.