Long-term follow-up and successful treatment of pulmonary alveolar proteinosis without hypercholesterolemia with statin therapy: a case report

Pathogenesis-driven treatment of primary pulmonary alveolar proteinosis

Pulmonary alveolar proteinosis (PAP) is a syndrome that results from the accumulation of lipoproteinaceous material in the alveolar space. According to the underlying pathogenetic mechanisms, three different forms have been identified, namely primary, secondary and congenital. Primary PAP is caused by disruption of granulocyte-macrophage colony-stimulating factor (GM-CSF) signalling due to the presence of neutralising autoantibodies (autoimmune PAP) or GM-CSF receptor genetic defects (hereditary PAP), which results in dysfunctional alveolar macrophages with reduced phagocytic clearance of particles, cholesterol and surfactant. The serum level of GM-CSF autoantibody is the only disease-specific biomarker of autoimmune PAP, although it does not correlate with disease severity. In PAP patients with normal serum GM-CSF autoantibody levels, elevated serum GM-CSF levels is highly suspicious for hereditary PAP. Several biomarkers have been correlated with disease severity, although they are not specific for PAP. These include lactate dehydrogenase, cytokeratin 19 fragment 21.1, carcinoembryonic antigen, neuron-specific enolase, surfactant proteins, Krebs von Lungen 6, chitinase-3-like protein 1 and monocyte chemotactic proteins. Finally, increased awareness of the disease mechanisms has led to the development of pathogenesis-based treatments, such as GM-CSF augmentation and cholesterol-targeting therapies.

A case of autoimmune pulmonary alveolar proteinosis responding to oral statin therapy

There is no approved drug treatment for autoimmune pulmonary alveolar proteinosis (APAP), although traditionally requires complex treatments such as whole lung lavage (WLL). We herein report on a 67-year-old man diagnosed with APAP. Treatment with atorvastatin (5 mg daily) resulted in significant improvement in symptoms, lung function, and computed tomography findings, with enhanced oxygenation, although serum anti-GM-CSF antibody levels remained elevated. This case suggests that the remission observed in this case could potentially be attributed to a direct effect of atorvastatin within the pulmonary alveoli. Statins may be considered as one of the treatment options for APAP.

Assessment of Statin Treatment for Pulmonary Alveolar Proteinosis without Hypercholesterolemia: A 12-Month Prospective, Longitudinal, and Observational Study

Background

Pulmonary alveolar proteinosis (PAP) is a rare disorder which is characterized by the accumulation of excessive surfactant lipids and proteins in alveolar macrophages and alveoli. Oral statin therapy has been reported to be a novel therapy for PAP with hypercholesterolemia. We aimed to evaluate the safety and efficacy of oral statin therapy for PAP without hypercholesterolemia.

Methods

In a prospective real-world observational study, 47 PAP patients without hypercholesterolemia were screened. Oral statin was initiated as therapy for these PAP patients with 12 months of follow-up.

Results

Forty PAP patients completed the study. 26 (65%) of 40 PAP patients responded to statin therapy according to the study criteria. Partial pressure of arterial oxygen (PaO2) and percentage of diffusion capacity predicted (DLCO%) significantly increased while disease severity score (DSS) and radiographic abnormalities decreased after 12 months of statin therapy (all p < 0.05). The factors associated with response were higher levels of granulocyte-macrophage colony-stimulating factor (GM-CSF) antibody and baseline total cholesterol/high-density lipoprotein cholesterol (TC/HDL) (p = 0.015 and p = 0.035, respectively). The area under the receiver operating characteristic curve (AUROC) of dose of atorvastatin for predicting the response to statin therapy for PAP was 0.859 (95% CI: 0.738-0.979, p < 0.001). The cutoff dose of atorvastatin was 67.5 mg daily with their corresponding specificity (64.3%) and sensitivity (96.2%). No severe side effects were observed during the study.

Conclusions

In PAP patients without hypercholesterolemia, statin therapy resulted in improvements in arterial blood gas (ABG) measurement, pulmonary function, and radiographic assessment.

A case of autoimmune pulmonary alveolar proteinosis with severe respiratory failure treated with segmental lung lavage and oral statin therapy

Pulmonary alveolar proteinosis (PAP) is a diffuse lung disease characterized by the accumulation of alveolar surfactants due to dysfunction of granulocyte-macrophage colony-stimulating factor-dependent cholesterol clearance. Whole-lung lavage is the current standard of care for PAP, but it can lead to the exacerbation of hypoxia. A medication targeting cholesterol homeostasis is a promising therapy for refractory PAP. We present a case of autoimmune PAP with severe hypoxia that was successfully treated with segmental lung lavage (SLL). Following SLL for disease relapse, statin treatment for dyslipidemia was started. After initiating statin treatment, the patient did not require bronchoalveolar lavage for 10 months.