The purpose of this study is to determine whether the use of rituximab is effective in treating pulmonary alveolar proteinosis by leading to an improvement in lung function and disease status.

The goal of this study is to conduct a prospective, open-label 6-month trial of rituximab in patients who present with symptomatic primary or idiopathic PAP. A total of 10 subjects with primary PAP will be enrolled over 12 months at East Carolina University. Patients over age 18 with a clinical diagnosis of moderate symptomatic idiopathic PAP, established by appropriate clinical history, radiographic and physiologic findings, presence of circulating anti-GM-CSF antibody, and confirmatory findings on bronchoscopy with bronchoalveolar lavage and/or open-lung biopsy will be recruited. Patients with newly diagnosed PAP or established disease may be considered for this study.

Inclusion Criteria:

• Diagnosis of primary PAP (new or chronic) with presence of anti-GM-CSF antibody
• Moderately symptomatic disease with PaO2 <70 on room air and on less than 6 L/min oxygen
• Able to give written informed consent and comply with the requirements of the study
• Adequate renal and liver function
• Negative serum pregnancy test (for women of child bearing age) and on acceptable birth control during and after study completion

Exclusion Criteria:

• Severe PAP and requires in-patient care and more urgent therapy with bilateral whole lung lavage
• Treatment with any investigational agent within 4 weeks of screening
• History of severe allergic or anaphylactic reactions to humanized or murine monoclonal antibodies
• History of HIV, recurrent significant infection or recurrent bacterial infections
• Known active bacterial, viral, fungal, mycobacterial, or other infection
• Ongoing use of high dose steroids (>10mg/day) or unstable steroid dose
• Significant cardiac or pulmonary disease or blood disorder