A Challenging Case of Influenza H1N1 Pneumonia and Pulmonary Alveolar Protienosis, Comprehensive Discussion of Disease-Disease Relationship in Terms of Causality, Cross-Reactivity, Outcome and Effect of Treatment

Abstract

Pulmonary alveolar proteinosis (PAP) is a rare lung disease characterized by the accumulation of amorphous lipoproteinaceous material in the distal air spaces due to defective surfactant clearance by alveolar macrophages. This leads to impaired gas exchange and arterial hypoxemia of varying degrees. Although autoimmune type of PAP is thought to be idiopathic, this focused report highlights the possible relationship between viral pneumonia and autoimmune PAP (APAP) in terms of causation, superinfection and effect of treatments. We report a newly diagnosed case of APAP with a possible viral causation “trigger” for the confirmed serum anti-granulocyte macrophage-colony stimulating factor (GM-CSF) antibody. To the best of our knowledge, this is the first report that describe and discuss this issue. The patient is a 38-year- old, ex-smoker woman who had had a progressively worsening dyspnea and a persistent, productive cough for more than 4 months. It was thought to be a community acquired pneumonia (CAP) case and was treated with multiple antibiotics which yielded no improvement in her condition. Physical examination revealed mild hypoxemia and minimal bilateral fine crepitations despite marked alveolar filling on chest X-ray (CXR). She underwent a bronchoscopic procedure that revealed PAP. The case also describes an acute flare up of the condition during the course of the disease caused by a confirmed H1N1 influenza infection. APAP should be considered in the differential diagnosis of recurrent pneumonia not responding to treatment. In this case report we suggest the possible role of viral causation “trigger” or cross-reactivity of GM-CSF antibodies that lead to APAP. We also describe the provided management, the response to the antiviral therapy and the diagnostic and management challenges that was encountered during the follow up.