Clinical features of <scp>LRP4</scp>/agrin‐antibody–positive myasthenia gravis: A multicenter study

<jats:title>Abstract</jats:title><jats:sec><jats:title>Introduction</jats:title><jats:p>Our aim in this study was to identify the prevalence and clinical characteristics of LRP4/agrin‐antibody–positive double‐seronegative myasthenia gravis (DNMG).</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>DNMG patients at 16 sites in the United States were tested for LRP4 and agrin antibodies, and the clinical data were collected.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Of 181 DNMG patients, 27 (14.9%) were positive for either low‐density lipoprotein receptor–related protein 4 (LRP4) or agrin antibodies. Twenty‐three DNMG patients (12.7%) were positive for both antibodies. More antibody‐positive patients presented with generalized symptoms (69%) compared with antibody‐negative patients (43%) (<jats:italic>P</jats:italic> ≤ .02). Antibody‐positive patients’ maximum classification on the Myasthenia Gravis Foundation of America (MGFA) scale was significantly higher than that for antibody‐negative patients (<jats:italic>P</jats:italic> ≤ .005). Seventy percent of antibody‐positive patients were classified as MGFA class III, IV, or V compared with 39% of antibody‐negative patients. Most LRP4‐ and agrin‐antibody–positive patients (24 of 27, 89%) developed generalized myathenia gravis (MG), but with standard MG treatment 81.5% (22 of 27) improved to MGFA class I or II during a mean follow‐up of 11 years.</jats:p></jats:sec><jats:sec><jats:title>Discussion</jats:title><jats:p>Antibody‐positive patients had more severe clinical disease than antibody‐negative patients. Most DNMG patients responded to standard therapy regardless of antibody status.</jats:p></jats:sec>