On the other hand, CSF:serum ratio for C4a was increased in MS patients compared to HC, but CSF C4a levels showed moderate correlation with CSF IgG (r = 0.53, p = 0.01) while not with CSF albumin, suggesting C4a CSF was more likely the result of intrathecal synthesis (80). The gene discussed is C4A; the disease is myeloid sarcoma.