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Diagnostic Challenges of LRP4 Antibody Testing in Myasthenia Gravis: A Case Series of Four LRP4 Positive Cases With Uncertain Diagnostic Significance

Kinnard KR, Khalid E

Case reports in neurological medicine, 2026

Abstract

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.

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Evidence Hub reads this as a case series, done in people. Its evidence level is 5 of 5 (Very low · case / narrative / animal / in vitro / in silico). Case reports, narrative reviews, and animal, cell or computer-model studies give the weakest evidence for human health.

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