Thread by @nickmmark

Non-COVID teaching case: A middle aged woman with myelodysplastic syndrome presents with severe dyspnea and hypoxemia requiring intubation. She fails to improve with antibiotics. A chest CT is performed prompting a bronchoscopy. The results of BAL are shown:
#FOAMed #FOAMcc
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What is going on here?
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Pulmonary Alveolar Proteinosis (PAP) is a rare lung disease characterized by accumulation of surfactant-derived lipoproteins in the alveoli. This milky proteinaceous fluid impairs gas exchange and leads to hypoxemia and respiratory failure.
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Radiographically, PAP causes ‘crazy paving’, which is the combination of ground glass and intralobular thickening
PAP is diagnosed by bronchoscopy: bronchioalveolar lavage (BAL) may reveal a milky fluid, and PAS positive macrophages are seen pathologically.
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Healthy lungs constantly produce and reabsorb surfactant.

PAP is caused by a derangement of surfactant homeostasis due to dysfunction of alveolar macrophages (AM).

This can occur due to impaired GM-CSF signaling, preventing proper AM maturation.
➡️link.springer.com/chapter/10.100…
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There are many causes of PAP, which is broadly divided into primary, secondary, or congenital.

Most cases involve ineffective GM-CSF signaling, which may be due to auto-antibodies against GM-CSF or a relative deficiency in the setting of malignancy, infection, or inflammation
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In some cases, PAP resolves with tx of the underlying cause (e.g. treat infection, cancer, etc).

Because PAP involves abnormal GM-CSF signaling, several other therapeutic strategies can be used: inhibit B-cells, remove auto-Ab, supplement GM-CSF, etc
➡️nature.com/articles/s4157…
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In severe cases, whole lung lavage (WLL) is necessary: Ventilate one lung with a double lumen ETT while the other lung is repeatedly lavaged with saline.

*DOZENS of LITERS* may be required to clear proteinaceous fluid from the lung.

For a details see ncbi.nlm.nih.gov/pmc/articles/P…
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🥡Points:
-Pulmonary alveolar proteinosis (PAP) is a rare cause of respiratory failure caused by AM dysfxn
-chest CT shows ‘crazy paving’ & BAL shows milky PAS+ fluid
-there are many causes; most involve impaired GM-CSF signaling
-severe cases are treated w/ whole lung lavage
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