Skeletal muscle antibodies in thymoma patients without myasthenia gravis

Advances in the treatment of myasthenia gravis

Myasthenia gravis (MG) should be classified according to antibody status (acetylcholine, MuSK, LRP4, titin), thymus (hyperplasia, neoplasia, atrophy), age at debut (< or >50 years), symptom localization (generalized, ocular) and severity. With optimal treatment, the prognosis is good in terms of daily functions, quality of life and survival. Symptomatic treatment with acetylcholine esterase is usually combined with immunosuppression. A combination of prednisolone and azathioprine remains the first choice alternative, whereas rituximab is a promising second choice drug for severe generalized MG. Thymectomy is recommended for early-onset, generalized MG and for thymoma MG. In acute exacerbations including MG crisis, intravenous immunoglobulin and plasma exchange have good and similar effects. MG in young females needs therapeutic considerations regarding potential pregnancy.

Characterization of acetylcholine receptor antibodies in a patient with primary biliary cirrhosis

Antibodies against the acetylcholine receptor were found in a patient with primary biliary cirrhosis. The patient had no clinical or electrophysiological evidence of disturbed neuromuscular function. The antibodies were of both IgG and IgM isotype. Following passive transfer, these antibodies showed the same capacity to bind in vivo to mouse muscle receptors as immunoglobulins from patients with myasthenia gravis. The affinity of the antibodies was high and comparable to that found in myasthenia gravis patients.

Neuromuscular disorders and thymoma

We describe a patient who had asymmetrical atrophy of limb muscles and myasthenic weakness of neck, facial, and bulbar muscles. Electrophysiological tests indicated myasthenia gravis of facial muscles and changes consistent with an asymmetrical motor neuropathy as a cause of the muscle atrophy. Both conditions occurred as complications of a locally invasive thymoma, and both failed to improve after surgery and radiation but substantially improved with subsequent treatment by corticosteroids, azathioprine, and plasmapheresis. Review of the literature disclosed that several neuromuscular conditions may be associated with thymoma, the commonest being myasthenia gravis. Muscle atrophy may occur in 10% of patients who have myasthenia gravis, whether associated with or without thymoma. Its mechanism is debated, and further studies are needed, but observations in our patient suggest the atrophy is due to a motor neuropathy. Primary treatment of the thymoma by surgery, irradiation if the tumor is invasive, and immunosuppressive therapy for neuromuscular complications offers a relatively good prognosis for this group of patients.