OCLN and Friedreich ataxia: Molecularly, the inflammatory cytokine IL-6 is upregulated in FRDA circulation, a pathway which in neurodegeneration is linked to decreased protein expression of occludin and cadherin (an adherens junction protein), causing BBB breakdown (Cohen et al., 2013; Alsaffar et al., 2018; Khan et al., 2021; Yang et al., 2022).