NEFL and multiple sclerosis: These findings in peripheral neuropathies are aligned with strong evidence demonstrating increased concentrations of NFL in several central nervous system conditions, including ALS,6,57 Alzheimer Disease,6,58 multiple sclerosis,6,8 and traumatic brain injury.7,59 NFL’s functional role in axonal growth and stability and its high expression in neuronal tissue60 (eFigure 2 in Supplement 1) make it a robust neuronal biomarker.61 Our data corroborate using NFL as a blood-based biomarker not only for central but also for peripheral neuropathies.