The prevalence and characteristics of agrin and low-density lipoprotein-related receptor protein 4 (LRP4) antibody-positive amyotrophic lateral sclerosis (ALS) patients were studied.

We tested 82 ALS patients and 59 controls for agrin and LRP4 antibodies using enzyme-linked immunoassay (ELISA).

We found that 13.8% of ALS patients had agrin antibodies, and 9.8% had LRP4 antibodies. Women with ALS are twice as likely as men to have antibodies. Agrin-positive ALS patients are younger than agrin-negative ALS patients.

Antibodies to agrin and LRP4 are found in ALS patients. It must be determined whether these antibodies are pathogenic. Because antibody-positive patients have upper as well as lower motor neuron findings, the antibodies' effects cannot be explained solely by their actions at the neuromuscular junction. A breakdown in interneuronal signaling may be the cause of ALS. Further research is needed to resolve this question. Muscle Nerve, 2016 Muscle Nerve 55: 430-432, 2017.