HSD3B7 and myeloid sarcoma: Reduced concentrations of CH25H in the CSF of patients with MS could be activating a feedback mechanism which, in response to reduced oxysterol content, may downregulate the degrading enzyme (HSD3B7) and at the same time upregulate EBI2. However, such speculations require detailed measurements of changes in the oxysterol levels and have not been investigated here.