Effectiveness of Rituximab in Pediatric OMS Patients.

Inclusion Criteria:

* written consent from parents
* have symptomatic OMS
* have CSF B-cell expansion (\>1% B-cells)
* adequate renal function as indicated by normal BUN \[10-25 mg/dL\] and creatinine \[0.4-1.2 mg/dL\]
* adequate liver function, as indicated by up to 2x normal AST \[0-35 U/L\] and ALT \[0-35 U/L\].
* men and women of reproductive potential must agree to use an acceptable method of birth control during treatment and for twelve months after completion of treatment

Exclusion Criteria:

* treatment with any investigational agent within 4 weeks of screening or 5 half-lives of the investigational drug (which ever is longer)
* receipt of a live vaccine within 4 weeks prior to enrollment
* previous treatment with Rituximab
* prior antibody therapy (does not include IVIg) within past 6 months
* history of severe allergic or anaphylactic reactions to humanized or murine monoclonal antibodies
* history of HIV (patients considered high risk will be screened)
* history of hepatitis B and/or hepatitis C (patients considered high risk will be screened)
* history of recurrent significant infection or history of recurrent bacterial infections
* known active bacterial, viral fungal mycobacterial, or other infection (including tuberculosis or atypical mycobacterial disease, but excluding fungal infections of nail beds) or any major episode of infection requiring hospitalization or treatment with i.v. antibiotics within 4 weeks of screening or oral antibiotics within 2 weeks prior to screening
* pregnancy (a negative serum pregnancy test should be performed for all women of childbearing potential within 7 days of treatment)
* significant cardiac (symptomatic arrhythmias or symptomatic structural heart disease) or pulmonary disease (including obstructive pulmonary disease)
* concomitant chemotherapy
* hemoglobin: \>13.5 gm/dL or \<10.0 gm/dL
* platelets: \<100,000/mm or \>500,000/mm K/cumm