Case Report: Anti-cavin-4-positive immune-mediated rippling muscle disease co-occurring with isolated ocular myasthenia gravis.

Immune-mediated rippling muscle disease (iRMD) is a rare autoimmune myopathy characterized by mechanically triggered, wave-like skeletal muscle contractions. Its coexistence with myasthenia gravis (MG) has been described, but detailed clinicopathological and longitudinal characterization of anti-cavin-4-positive iRMD coexisting with isolated ocular MG remains limited. Here, we report a 35-year-old man who developed painless, water-like rippling movements of the right thigh in 2023, followed by occasional palpitations and mild creatine kinase elevation in 2024. In July 2025, he developed fluctuating right ptosis without diplopia, bulbar symptoms, or limb weakness. Serology showed anti-acetylcholine receptor antibody positivity and high-titer anti-cavin-4 antibodies. Electromyography revealed mild myogenic changes with electrically silent rippling activity. Muscle biopsy showed mild myopathic changes and mosaic caveolin-3 expression. Chest CT showed no thymic hyperplasia or thymoma, and cardiac evaluation showed no structural heart disease or clinically significant arrhythmia. These findings supported anti-cavin-4-positive iRMD coexisting with isolated AChR-positive ocular MG. At follow-up, the patient reported reduced rippling activity, preserved limb strength, and persistent mild fatigue-related ptosis. Among the cases identified in our search, this was the youngest documented case with isolated ocular MG and the first anti-cavin-4-positive ocular-MG case with muscle-biopsy documentation. The case extends the documented age and mild-severity spectrum of iRMD associated with MG or AChR antibody positivity.