obsolete pneumonia true A pneumonitis that is characterized by an inflammatory illness of the lung resulting from a variety of causes including infection with bacteria, viruses, fungi, or parasites, and chemical or physical injury to the lungs. Its cause may also be officially described as idiopathic, that is, unknown, when infectious causes have been excluded. doid/symp duplicate - reviewed 10/2022 & determined to be a disease SYMP:0019168 symptoms