(Science: oncology, tumour) An immunologic disorder of unknown cause where there is proliferation of histiocytes (a type of cell in the immune system) in the bloodstream. The disorder is characterised by inflammation of the bronchioles and small pulmonary vessels that leads to fibrosis and destruction of alveolar cell walls. Cigarette smoking is considered a risk factor. Individuals with this disorder are also at increased risk for spontaneous pneumothorax.
symptoms include cough, chest pains, shortness of breath, fever, weight loss and malaise. Bronchoscopy with biopsy confirms the diagnosis. Childhood forms exist and cause more systemic symptoms and findings such as failure to thrive, weight loss, fevers, irritability, rash and bone pains. Treatment is with corticosteroids.