Anti-LRP4 autoantibodies in Chinese patients with myasthenia gravis.

INTRODUCTION: We assessed antibodies against low-density lipoprotein receptor-related protein 4 (LRP4-Ab) in a Chinese population with myasthenia gravis (MG).

METHODS: Serum samples from 116 patients and 80 controls were collected. Acetylcholine receptor antibodies(AChR-Ab) and muscle-specific receptor tyrosine kinase antibodies (MuSK-Ab) were tested using an enzyme-linked immune absorption assay, and LRP4-Ab was identified using a cell-based assay. MG patients with neither AChR-Ab nor MuSK-Ab were defined as double-seronegative MG (dSN-MG).

RESULTS: Two of 116 (1.7%) of all patients and 2 of 50 (1%) dSN-MG patients were positive for LRP4-Ab. These 2 patients had ocular MG. Following treatment with acetylcholinesterase inhibitor and prednisone, both achieved full remission.

CONCLUSIONS: This study shows that LRP4-Ab is a pathogenic antibody in MG. LRP4-MG seems to be characterized by mild disease severity and favorable therapeutic effect in contrast with other types of MG. Muscle Nerve 56: 938-942, 2017.