Eosinophilic crystalline pneumonia, an age-related lesion in mice.

Eosinophilic crystalline pneumonia (ECP), also known as acidophilic macrophage pneumonia (AMP), is a common intrapulmonary lesion that increases in prevalence with age in mice, especially those on a C57BL/6 and 129Sv background. Gross changes may be evident in severe cases as lobar to diffuse red to brown foci throughout the lungs, which fail to collapse. Definitive diagnosis is by histopathology, which shows the accumulation of brightly eosinophilic crystals within macrophages or free within lumens of alveolar spaces and conducting airways. Granulocytes, multinucleated giant cells, and epithelial hyalinosis may also be present in affected areas of the lung. The disease may represent a cause of morbidity and mortality when other disease processes interfere with clearance, leading to the accumulation of crystals and crystal laden macrophages in airways, resulting in dyspnea. Other anatomic locations may be affected by epithelial hyalinosis and/or crystals as part of the syndrome, including respiratory tract, stomach, gall bladder, bile duct, and pancreatic duct.