Myasthenia gravis is an autoimmune disorder characterized by muscle weakness due to impaired neuromuscular transmission. While antibodies against the acetylcholine receptor and muscle-specific kinase are commonly used for diagnosis, a subset of patients remains seronegative, necessitating alternative biomarkers. Low-density lipoprotein receptor-related Protein 4 antibodies have emerged as a potential diagnostic marker in seronegative myasthenia gravis cases. However, misleading positive results have obscured diagnosis and management. This study explores the clinical relevance of low-density lipoprotein receptor-related Protein 4 antibodies in myasthenia gravis through four patient case studies. Patients presenting with concern for myasthenia gravis underwent a comprehensive diagnostic evaluation, including antibody testing for acetylcholine receptor, muscle-specific kinase, and low-density lipoprotein receptor-related Protein 4. Volitional single-fiber electromyography was also performed. All tests were employed per standardized laboratory protocols. All four patients were initially evaluated for suspected myasthenia gravis; however, despite positive low-density lipoprotein receptor-related Protein 4 antibody results, comprehensive clinical and electrophysiological evaluation ultimately excluded the diagnosis of myasthenia gravis. These cases underscore the limitations of low-density lipoprotein receptor-related Protein 4 antibody testing.
Kinnard et al. (Thu,) studied this question.