PROTOCOL ENTRY CRITERIA:

--Disease Characteristics-- Mild or moderate generalized myasthenia gravis Grade 2 or 3 myasthenia gravis according to a modified Osserman groups system Ocular myasthenia gravis alone or myasthenia gravis in crisis not eligible Must have elevated acetylcholine receptor antibody titer No evidence of thymoma on chest CT or MRI No immunoglobulin-A deficiency less than 5 mg/dL Group 1: Patients who have not received other immunosuppressive therapy in the past, including intravenous immunoglobulin Group 2: Patients considered steroid-dependent

Considered steroid-dependent if demonstrated improvement following initiation of corticosteroid therapy but continue to have generalized weakness on examination despite receiving 20 mg of prednisone (or equivalent) every other day and experience unacceptable symptoms on lower doses Prednisone and other immunosuppressive drug doses must not have changed within last 4 weeks May have had other immunosuppressive medication (azathioprine, cyclosporine, cyclophosphamide) or have received plasma exchange if these treatments were not initiated in the 2 months prior to study enrollment Must be receiving immunosuppressive medication for at least 3 months prior to study

--Prior/Concurrent Therapy-- Endocrine therapy: Corticosteroid must be maintained at a constant dose during study Surgery: No thymectomy in the last 3 months Other: No plasmapheresis in the last 2 months --Patient Characteristics-- Age: 15 and over Weight: No greater than 80% above ideal body weight Hepatic: SGOT, SGPT, and alkaline phosphatase no greater than 1.5 times upper limit of normal (ULN) Renal: BUN no greater than ULN Creatinine no great than ULN Neurology: No history of relevant chronic degenerative, psychiatric, or neurologic disorder, other than myasthenia gravis, that can produce weakness or fatigue No altered consciousness, dementia, or abnormal mental status Pulmonary: Forced vital capacity at least 50% of predicted Not at high risk for aspiration Other: No active thyroid gland dysfunction as manifested by abnormal thyroid function tests or the need for current thyroid replacement Normal thyroid function tests required No other major relevant chronic or debilitating illnesses within 6 months of study Not pregnant or nursing Adequate contraception required of all fertile patients