We studied the relationship between descending pain modulation (ie, CPM), corticospinal excitability, and brain-derived neurotrophic factor (BDNF) as a marker of neuroplasticity, in MPS.3 In this cross-sectional study, we investigated the relationship between cortical excitability and BDNF levels in 33 women with chronic MPS who responded (n = 10, age: 48 ± 9 years) and did not respond (n = 23, age: 43 ± 15 years) to CPM. Here, BDNF is linked to mucopolysaccharidosis.