Diagnostic Challenges in Seronegative Myasthenia Gravis: A 27-Year-Old Patient Case
A 27-year-old woman with progressive fatigue, exercise intolerance, and fluctuating left eyelid ptosis has highlighted the diagnostic uncertainty inherent to suspected seronegative myasthenia gravis, cureus.com reported. Medical specialists established a working diagnosis of probable SNMG based on a distinct clinical phenotype and positive bedside testing, despite initial conventional antibody tests and single-fiber electromyography returning normal results. The patient presented with symptoms that worsened toward the end of the day and improved with rest, initially prompting normal routine laboratory work and cranial imaging. Subsequent neurological assessment introduced an ice-pack test, which produced a clear improvement in her eyelid ptosis. Thoracic imaging ruled out thymoma, and single-fiber electromyography of the orbicularis oculi muscle showed no objective electrophysiological confirmation of the autoimmune disorder.
Patient develops progressive symptoms after immunosuppressive therapy
Following the initial diagnostic uncertainty, physicians initiated a trial of pyridostigmine, which yielded only limited symptomatic relief. Due to the persistent and characteristic fluctuating phenotype alongside the positive ice-pack test and the exclusion of alternative diagnoses, clinicians established a working diagnosis of probable seronegative myasthenia gravis and started immunosuppressive therapy.
Over the subsequent two years, the patient experienced a generalization of her symptoms. She developed progressive limb fatigability, difficulty climbing stairs, intermittent dysphagia, and substantial functional limitations. The case shows the diagnostic limitations in suspected SNMG cases, where negative antibody and neurophysiological findings require careful longitudinal clinical reassessment rather than an automatic exclusion of the disease.
Frequently Asked Questions About Seronegative Myasthenia Gravis
What is seronegative myasthenia gravis?
Seronegative myasthenia gravis is a variant of the autoimmune neuromuscular disorder where patients display characteristic muscle weakness and fatigability, but conventional blood tests fail to detect disease-associated antibodies like AChR or MuSK.
Why are initial neurophysiological tests sometimes normal in ocular myasthenia gravis?
Repetitive nerve stimulation often has a lower diagnostic yield in ocular presentations compared to generalized disease, while single-fiber electromyography results can vary depending on disease severity and the specific muscle studied.
What role does the ice-pack test play in diagnosis?
The ice-pack test provides supportive bedside evidence when applied to patients experiencing eyelid ptosis, though physicians cannot use it in isolation to establish a definitive diagnosis.