Researchers Present Relationship Between aPAP-related Pulmonary Fibrosis, ANCA-associated Systemic Vasculitis

In a study entitled “Development of microscopic polyangiitis-related pulmonary fibrosis in a patient with autoimmune pulmonary alveolar proteinosis” published in BMC Pulmonary Medicine the authors report the first evidence of a relationship between ANCA-associated systemic vasculitis and aPAP-related pulmonary fibrosis.

Autoimmune pulmonary alveolar proteinosis (aPAP) is a rare lung disease which is caused by the presence of a self-directed antibody against a cytokine, a component released by immune cells called granulocyte-macrophage colony stimulating factor (GM-CSF). This disease is normally accompanied by an accumulation of surfactant lipids and proteins in the alveolar space within the lungs, thereby affecting pulmonary homeostasis.

The clinical course of aPAP is variable and in most severe cases, the patients can present with pulmonary fibrosis, a condition characterized by an excessive scar formation in the lung tissue. Until now, the relationship between this autoimmune disease (aPAP) and pulmonary fibrosis was not fully understood.

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The evidence for such pathogenetic relation came from this one case study. The patient, a 75-year-old Japanese man, was diagnosed with aPAP. However, no specific treatment was applied for his condition during a period of 3 years. During this period, the researchers found a significant increase of anti-neutrophil cytoplasmic antibody (ANCA). This antibody is widely used as a specific marker for a condition called ANCA-associated systemic vaculitis, which can destroy the blood vessels by inflammation. Notably, pulmonary fibrosis is a common complication in ANCA-associated systemic vaculitis, due to alveolar capillarities that is characterized by alveolar hemorrhage and is usually difficult to diagnose, but ultimately leads to fibrosis. This report is the first establishing an association between ANCA-related pulmonary fibrosis and aPAP. The authors provide data suggesting an intricate relationship between the pulmonary fibrosis developed during a normal aPAP condition and the presence ANCA-related systemic vaculitis.

Finally, the researchers highlight the need to further investigate the link between these two major conditions in order to improve our understanding and possible treatment of this life-threatening complication in aPAP patients.