Patient description: The patient is a 16-year-old girl recently diagnosed with myasthenia gravis, class IIa. She complains of diplopia and weakness affecting in her upper extremities. She had a positive anti-AChR antibody test, and her single fiber electromyography (SFEMG) was positive. She is on acetylcholinesterase inhibitor treatment combined with immunosuppressants. But she still has some symptoms. She does not smoke or use illicit drugs. She is not sexually active, and her menses are regular. Her physical exam and lab studies are not remarkable for any other abnormalities. BP: 110/75 Hgb: 11 g/dl WBC: 8000 /mm3 Plt: 300000 /ml Creatinine: 0.5 mg/dl BUN: 10 mg/dl Beta hcg: negative for pregnancy

Clinical trial eligibility criteria: eligible ages (years): 2.0-21.0,  Unspecified Childhood Solid Tumor, Protocol Specific Patients must have had histologic verification of malignancy at original diagnosis or relapse except in patients with intrinsic brain stem tumors, patients with optic pathway gliomas, and patients with pineal tumors and elevations of serum or cerebrospinal fluid (CSF) alpha-fetoprotein or beta-human chorionic gonadotropin (HCG) Patients must have either measurable or evaluable disease Patient's current disease state must be one for which there is no known curative therapy or therapy proven to prolong survival with an acceptable quality of life Karnofsky >= 50% for patients > 16 years of age and Lansky >= 50 for patients =< 16 years of age; Note: neurologic deficits in patients with central nervous system (CNS) tumors must have been relatively stable for a minimum of 1 week prior to study enrollment; patients who are unable to walk because of paralysis, but who are up in a wheelchair, will be considered ambulatory for the purpose of assessing the performance score Patients must have fully recovered from the acute toxic effects of all prior anti-cancer chemotherapy Myelosuppressive chemotherapy: patients must not have received myelosuppressive therapy within 3 weeks of enrollment onto this study (6 weeks if prior nitrosourea) Hematopoietic growth factors: at least 14 days after the last dose of a long-acting growth factor (e.g. Neulasta) or 7 days for short-acting growth factor; for agents that have known adverse events occurring beyond 7 days after administration, this period must be extended beyond the time during which adverse events are known to occur; the duration of this interval must be discussed with the study chair Biologic (anti-neoplastic agent): at least 7 days after the last of a biologic agent that is not a monoclonal antibody and enrollment on this study; for agents that have known adverse events occurring beyond 7 days after administration, this period must be extended beyond the time during which adverse events are known to occur; the duration of this interval must be discussed with the study chair Immunotherapy: at least 6 weeks since the completion of any type of immunotherapy, e.g. tumor vaccines Monoclonal antibodies: at least 3 half-lives must have elapsed after treatment with a monoclonal antibody and enrollment on this study  Pregnant or breast-feeding women will not be entered on this study; pregnancy tests must be obtained in girls who are post-menarchal; males or females of reproductive potential may not participate unless they have agreed to use an effective contraceptive method Patients receiving chronic systemic corticosteroids are not eligible; patients must have been off systemic corticosteroids for 7 days prior to enrollment Patients who are currently receiving another investigational drug are not eligible Patients who are currently receiving other anti-cancer agents are not eligible Patients who are currently receiving enzyme inducing anticonvulsants are not eligible Patients must not be receiving any of the following potent Cytochrome P450 family 3, subfamily A, polypeptide 4 (CYP3A4) inducers or inhibitors: erythromycin, clarithromycin, ketoconazole, azithromycin, itraconazole, grapefruit juice or St. John's worth Patients who are currently receiving therapeutic anticoagulants (including aspirin, low molecular weight heparin, and others) are not eligible Patients who are currently receiving angiotensin-converting enzyme (ACE) inhibitors are not eligible Patients who are receiving cyclosporine, tacrolimus or other agents to prevent either graft-versus-host disease post bone marrow transplant or organ rejection post-transplant are not eligible for this trial Patients who have an uncontrolled infection are not eligible