Autoimmune pulmonary alveolar proteinosis

Other Names: PAP; Pulmonary alveolar lipoproteinosis acquired; PAP acquired; Pulmonary alveolar proteinosis autoimmune; Pulmonary alveolar proteinosis acquired; Acquired pulmonary alveolar proteinosis

Autoimmune pulmonary alveolar proteinosis (aPAP) is a rare autoimmune lung disorder. It is the most common form (90% of the cases) of pulmonary alveolar proteinosis (PAP). Most cases affect adults between the ages of 20-50 years.

Cause

Autoimmune PAP is caused by an immune system malfunction, due to IgG antibodies that block the granulocyte-Macrophage Colony Stimulating Factor (GM-CSF) effect. GM-CSF is a protein that regulates clearance of surfactant (a mix of protein and fat) by alveolar macrophages. The surfactant pile up in the air sacs of the lungs (alveoli), and eventually lead to an inability to breath. Other PAP forms include congenital PAP, a very rare form that occurs in some newborns, caused by disorders of surfactant production; hereditary PAP, where people are born with genetic mutations that destroy the function of the proteins (receptors) on alveolar macrophages that interact with GM-CSF; and, secondary PAP, which occur in people with another disease or dust exposure.

Signs and symptoms

Some people may not show symptoms, while others may have progressive difficulty breathing and shortness of breath upon exertion. Other signs and symptoms may include a dry, chronic cough; fatigue; weight loss; chest pain; and a general feeling of ill health. In rare cases, coughing up of blood, rounding and swelling of the tips of the fingers, and cyanosis may be present.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Intraalveolar phospholipid accumulation

30%-79% of people have these symptoms

• Abnormal circulating protein level
• Abnormality of the upper respiratory tract(Upper respiratory tract issues)
• Autoimmune antibody positivity
• Clubbing(Clubbing of fingers and toes)
• Cyanosis(Blue discoloration of the skin)
• Decreased DLCO
• Dyspnea(Trouble breathing)
• Foam cells
• Hypoxemia(Low blood oxygen level)
• Increased lactate dehydrogenase level
• Restrictive ventilatory defect(Stiff lung or chest wall causing decreased lung volume)

5%-29% of people have these symptoms

• Cough(Coughing)
• Crackles
• Crazy paving pattern on pulmonary HRCT

1%-4% of people have these symptoms

• Anti-granulocyte-macrophage colony stimulating factor antibody positivity
• Brain abscess
• Chest pain
• Fatigue(Tired)
• Fever
• Hemoptysis(Coughing up blood)
• Inspiratory crackles
• Lung abscess
• Weight loss

Diagnosis

The health care provider will listen to the lungs with a stethoscope and may hear crackles (rales) in the lungs. Often, the physical examination is normal.

The following tests may be done:

• Bronchoscopy with saline wash of the lungs (lavage)
• Chest x-ray
• CT scan of the chest
• Lung function tests
• Open lung biopsy (surgical biopsy)

Treatment

• The treatment of PAP varies from case to case depending upon the form of PAP and the age of an affected individual and severity of the disease. About one-third of individuals with idiopathic PAP (of unknown cause) will improve without treatment (spontaneous remission).
• Patients with moderate or severe respiratory problems due to autoimmune PAP can be treated by a whole lung lavage, a procedure in which one lung is cleansed with a salt solution while the other is pumped with pure oxygen. In some cases, the procedure may need to be performed once; in others it may need to be repeated many times over several years. Generally, one lung is lavaged in the first procedure, followed by lavage of the opposite lung one to two weeks later.
• A treatment using recombinant granulocyte macrophage-colony stimulating factor(GM-CSF) given by nose, or with a subcutaneous injection is not approved for use in autoimmune PAP yet, but soon may be an effective option.
• Lung transplantation has been used to treat adults with PAP as a last resort. According to the medical literature, in some cases, PAP has recurred in adults who have received lung transplantation.
• Treatment options for patients with secondary and hereditary PAP are less clear and depend in part on the specific cause. In secondary PAP, removal and avoidance of the causative agent (e.g., silica exposure) or treatment of the underlying disorder may improve symptoms. For neonates with severe congenital PAP, lung transplantation is the only treatment that appears to improve outcome.

NIH genetic and rare disease info

• NIH info on Autoimmune pulmonary alveolar proteinosis

Autoimmune pulmonary alveolar proteinosis is a rare disease.

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