What is lymphocytic interstitial pneumonia (LIP)?
LIP is a lymphoproliferative response in the chest, often in children with human immunodeficiency virus (HIV) infection. On chest radiography, a diffuse reticulonodular pattern with central predominance may be seen along with bilateral hilar lymphadenopathy, although peribronchiolar thickening alone or a normal appearance may also be encountered. On CT, multiple perilymphatic interstitial micronodules are typically visualized. This pattern is more common in children whereas in adults, thin-walled air-filled cysts and pulmonary ground glass opacities are more often encountered.