Interstitial pneumonia (infiltrating lung disease) in Langerhans cell histiocytosis. Axial computed tomography (CT) scan through the lungs (dark blue) of a 28-year-old male patient with Langerhans cell histiocytosis, showing interstitial pneumonia. Langerhans cell histiocytosis is a disease in which proliferations of Langerhans cells, abnormal cells deriving from bone marrow, collect in the organs provoking inflammation. In this case the condition developed in the lungs producing interstitial pneumonia, inflammation in the tissue around the alveoli (air sacs) of the lungs, with formation of nodules and thick walled cysts.