Significantly higher total tau concentration was measured in MS patients with higher lesion load in brain MRI (≥9 versus <9 lesions; 168.33 pg/mL, IQR 111.67–222.32 and 73.33 pg/mL, IQR -32.13–139.29-, p = 0.021). The gene discussed is MAPT; the disease is myeloid sarcoma.