The mean CSF BAFF concentration, which was elevated in untreated OMS and OIND, correlated with OMS severity category (P = 0.006), and reduction by adrenocorticotropic hormone or corticotropin (ACTH) (−61%) or corticosteroids (−38%) was seen at each level of severity. Here, POMC is linked to opsoclonus-myoclonus syndrome.