U1 Small Nuclear Ribonucleoprotein Autoantibodies Reflect the Disruption of the Blood–Nerve Barrier in Guillain–Barré Syndrome

We recently identified the U1 small nuclear ribonucleoprotein (U1-snRNP) antibodies in patients with Guillain–Barré syndrome (GBS), which is associated with the breakdown of the blood–nerve barrier (BNB). The objective of this study was to clarify the clinical significance of U1-snRNP antibodies in patients with GBS and its variants. We measured U1-snRNP antibodies using an enzyme-linked immunosorbent assay from the serum samples of patients with GBS (n = 106), Miller Fisher syndrome (MFS) (n = 24), and MFS/GBS overlap syndrome (MFS/GBS, n = 8). We compared the clinical characteristics of U1-snRNP positive and U1-snRNP negative GBS patients (n = 106). The cerebrospinal fluid (CSF)/serum albumin quotient (QALB)/QALBLIM calculated as(age/15) + 4) was calculated. The prevalence of U1-snRNP antibody positivity was 39% (41/106) in GBS, 0% (0/24) in MFS, and 50% (4/8) in MFS/GBS. The rate of U1-snRNP antibody positivity in the GBS and MFS/GBS groups was significantly higher than that in the MFS group. Levels of CSF proteins and QALB/QALBLIM were higher in U1-snRNP antibody-positive GBS than in U1-snRNP antibody-negative GBS among all GBS patients, as well as GBS patients with a preceding Campylobacter jejuni infection or AIDP. In conclusion, the U1-snRNP antibody-positive GBS group had a more severe breakdown of the BNB in U1-snRNP antibody-positive GBS patients than in U1-snRNP-negative GBS patients. The presence of U1-snRNP antibodies may be a clinical biomarker for predicting the progression of MFS to MFS/GBS.