Microaspiration
Aliya N. Husain, MD
Ilyssa O. Gordon, MD, PhD
Key Facts
Terminology
Microscopic aspiration of gastric contents usually associated with symptoms of GERD
Clinical Issues
GERD is common in lung transplant patients
May be asymptomatic or present with
Repeated episodes of ACR
Symptoms of GERD
Microscopic Pathology
Exogenous lipoid pneumonia
Single or multiple large fat vacuoles within macrophages
Multinucleated giant cells within alveoli or interstitium ± foreign material
Top Differential Diagnoses
Rejection: ACR or chronic airway rejection
Artifact: Air bubbles in tissue
 Histologic changes of microaspiration can be very subtle and easily missed, as shown here. Within the alveolar spaces, there are 2 multinucleated giant cells with large vacuoles  . |
 Not all vacuoles are due to aspiration of lipid material. The holes shown here  are likely to be air artifacts. They are not intracellular and can be easily mistaken for exogenous lipoid pneumonia. |
TERMINOLOGY
Synonyms
Exogenous lipoid pneumonia
Definitions
Microscopic aspiration of gastric contents usually associated with symptoms of gastroesophageal reflux disease (GERD)
ETIOLOGY/PATHOGENESIS
Multifactorial Predisposition to GERD
Diminished cough reflex
Transection of bronchial nerves during transplant operation
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