ELP1 and neurodegenerative disease: FD is a congenital neurodegenerative disease caused by a point mutation in IkB kinase complex-associated protein (IKBKAP), which results in variable and tissue-specific skipping of exon 20 in the IKBKAP gene and reduces the yield of the functional IKAP protein, a scaffold protein involved in neurogenesis, neuronal survival, and peripheral tissue innervation [140].