Low-Density Lipoprotein Receptor-Related Protein 4-Positive Myasthenia Gravis in a Double-Seronegative, Electromyography-Negative Patient.

We describe a patient with ocular myasthenia gravis, where single-fiber electromyography and testing for acetylcholine receptor and muscle-specific kinase antibodies were negative. However, antibodies to low-density lipoprotein receptor-related protein 4 (LRP4) were positive, and this prompted appropriate management. We recommend that testing for LRP4 antibodies be considered when the clinical suspicion for myasthenia gravis is high despite negative conventional diagnostic tests.