• Evaluate symptomatic, physiologic and radiographic effects of therapy [ Time Frame: 6-months ] [ Designated as safety issue: No ]
  

• Evaluate the overall tolerability of therapy and the requirement for therapeutic whole-lung lavage [ Time Frame: 6-months ] [ Designated as safety issue: No ]
  

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