NBIA Syndromes: A Step Forward from the Previous Knowledge

A disturbed iron metabolism may damage brain and trigger disorders known as neurodegeneration with brain iron accumulation (NBIA). NBIAs are rare, inherited disorders in which responsible mutations affect the function of proteins that participate in tissue iron homeostasis. Accumulated iron, which may be recognized as a low signal intensity on T2-weighted MRI images, oftentimes points to a diagnosis. Recent genetic discoveries confirm that NBIA is not a homogenous group of diseases. Fifteen different NBIAs have been described to date; among these, autosomal recessive inheritance was reported in 13, and autosmal dominant and X-linked dominant inheritance in one disease, respectively. Among NBIAs, the most common is pantothenate kinase-associated neurodegeneration (PKAN-NBIA 1) (30%-50% of all NBIA cases), that occurrs as a consequence of the autosomal recessive mutation in PANK2 gene, followed by phospholipase 2-associated neurodegeneration (PLAN, NBIA 2), due to mutation in PLA2G6 gene, and mitochondrial membrane protein-associated neurodegeneration (MPAN) with the underlying C19orf12 mutation [Table 1]. NBIAs are characterized by complex motor presentations from early-onset degeneration and premature fatality to adult-onset parkinsonism and dystonia. Epileptic seizures, pyramidal signs, visual disorders, and cognitive deterioration can develop. NBIAs are often refractory to therapeutical strategies, although certain interventions may provide significant symptomatic relief in selected patients. In this review, we discuss the expanding clinical spectrum of these complex and rare syndromes, their genetic and imaging features, and potential therapeutical targets and strategies.