In the whole MS group and in PMS patients, GFAP correlated with NfL in CSF (Spearman rho = 0.3 and 0.5, p = 0.007 and 0.003, respectively) and serum (Spearman rho = 0.4 for both, p < 0.001 and = 0.01, respectively). The gene discussed is GFAP; the disease is premenstrual tension.