Coexistence of Acute Demyelinating Polyneuropathy and LRP4-Positive Myasthenia Gravis

Guillain-Barré syndrome (GBS) and myasthenia gravis (MG) are rare autoimmune disorders that may share overlapping features such as ophthalmoparesis, limb weakness, and bulbar symptoms, complicating the differential diagnosis. Coexistence of GBS and MG or chronic inflammatory demyelinating polyneuropathy and MG, particularly the low-density lipoprotein receptor-related protein 4 (LRP4) antibody-positive subtypes, is extremely rare. We present such a case to highlight diagnostic challenges.

A 46-year-old man presented with distal weakness, sensory loss, facial diplegia, and dyspnea. Nerve conduction studies revealed demyelinating features, and cerebrospinal fluid analysis showed albuminocytologic dissociation. An acute demyelinating polyneuropathy, most likely GBS, was suspected, and clinical improvement was observed following plasmapheresis. Three weeks later, new symptoms including dysarthria and worsening bulbar weakness emerged. Repetitive nerve stimulation showed a decremental response. LRP4 antibodies were positive, confirming MG. The patient improved with intravenous immunoglobulin, corticosteroids, pyridostigmine, and azathioprine.

This case underscores the rare coexistence of acute demyelinating polyneuropathy and LRP4-positive MG. In acute demyelinating polyneuropathy patients with relapsing or worsening symptoms, coexisting MG should be considered. Comprehensive electrophysiological evaluation and antibody testing, including LRP4, are essential for the accurate diagnosis of both conditions.