Isolated Bilateral Triceps Weakness in Myasthenia Gravis

Area of Science:

• Neurology
• Immunology

Background:

• Myasthenia gravis (MG) is an autoimmune disorder affecting neuromuscular junctions, typically causing ocular, facial, or neck muscle weakness.
• Selective or dominant triceps muscle weakness is an uncommon manifestation of MG.

Observation:

• A 45-year-old male patient presented with initial diplopia and ptosis, later developing bilateral triceps weakness.
• The patient had a history of thymectomy and was on pyridostigmine and prednisone treatment.
• Repetitive nerve stimulation confirmed decremental responses in the triceps muscles.

Findings:

• The case illustrates a rare form of myasthenia gravis characterized by predominant triceps muscle weakness.
• Acetylcholine receptor antibodies were positive, confirming the autoimmune etiology.
• The development of triceps weakness occurred despite established MG treatment and a decade of stability.

Implications:

• Recognizing this rare MG presentation can prevent diagnostic delays and unnecessary investigations.
• Prompt identification facilitates targeted treatment strategies for improved patient outcomes.
• This case expands the understanding of clinical variability in myasthenia gravis.