pneumonia

Inflammation of the lung parenchyma characterized by consolidation of the affected part, the alveolar air spaces being filled with exudate, inflammatory cells, and fibrin. Most cases are due to infection by bacteria or viruses, a few to inhalation of chemicals or trauma to the chest wall, and a small minority to rickettsiae, fungi, and yeasts. Distribution may be lobar, segmental, or lobular; when lobular and in associated with bronchitis, it is termed bronchopneumonia. SEE ALSO: pneumonitis. [G. fr. pneumon, lung, + -ia, condition]

- acute interstitial p. a severe and usually fatal form of p. occurring primarily in infants; usually considered a form of hypersensitivity pneumonitis.

- alcoholic p. p. occurring in patient with alcoholism, usually after a period of intoxication with stupor, resulting in aspiration.

- anaerobic p. p. caused by bacteria usually originating in the mouth, especially in the presence of periodontal disease; cavitation common.

- apex p., apical p. p. of the apex or apices.

- aspiration p. bronchopneumonia resulting from the inhalation of foreign material, usually food particles or vomit, into the bronchi; p. developing secondary to the presence in the airways of fluid, blood, saliva, or gastric contents. SYN: deglutition p..

- atypical p. p. caused by a nonbacterial pathogen, classically caused by Mycoplasma pneumoniae, but generally used to refer to any nonbacterial p. with mild systemic symptoms, including viral. See primary atypical p..

- bacterial p. infection of the lung with any of a large variety of bacteria, especially Streptococcus pneumoniae (pneumococcus).

- bilious p. p. following aspiration of gastric contents containing bile.

- bronchial p. SYN: bronchopneumonia.

- caseous p. a form of severe pulmonary tuberculosis in which tubercles are not prominent, but with a diffuse extensive cellular infiltration that undergoes caseation affecting large areas of lung.

- central p. a form of p. in which exudation is confined for a time to the central portion of a lobe or the hilar region. SYN: core p..

- chemical p. p. caused by inhalation of toxic gas, such as the war gases phosgene or chlorine; exudation into alveoli causes the lungs to be edematous and hemorrhagic; large amounts of fluid that fill the air passages block gaseous exchange; recovery occurs, permanent damage of the lungs remains, and recurrent pulmonary infections are common.

- chronic p. vague or indefinite term for long-standing inflammation of pulmonary tissue of any etiology.

- chronic eosinophilic p. a disease characterized by night sweats, exertional dyspnea, occasional wheezing, and peripheral eosinophilia. X-rays show peripheral, nonsegmental pulmonary infiltrates that can be nodular with cavitation. Responds to treatment with corticosteroids. SYN: Carrington disease.

- community-acquired p. p. caused by any organism found regularly outside the hospital; common organisms include Streptoccum pneumoniae, Haemophilus influenza, Mycoplasma, as opposed to hospital-acquired or nosocomical p..

- congenital p. p. in the newborn, infection being contracted prenatally.

- core p. SYN: central p..

- deglutition p. SYN: aspiration p..

- desquamative p. relatively rare form of p. with homogeneous filling of alveolar air spaces with macrophages and a few type II epithelial lining cells, some alveolar septal infiltration with inflammatory and connective tissue cells; usually idiopathic, but some cases have been reported in association with drugs or underlying systemic connective tissue disease; rarely progresses to end-stage lung disease.

- desquamative interstitial p. (D.I.P.) diffuse proliferation of alveolar epithelial cells, which desquamate into the air sacs and become filled with macrophages, accompanied by interstitial cellular infiltration and fibrosis; gradual onset of dyspnea and nonproductive cough occurs.

- p. dissecans SYN: p. interlobularis purulenta.

- double p. lobar p. involving both lungs.

- embolic p. infarction following embolization of a pulmonary artery or arteries.

- eosinophilic p. SYN: Loeffler syndrome I. SYN: eosinophilic pneumonopathy.

- fibrous p. a process affecting pulmonary tissue and leading to deposition of collagen, either interstitially or in alveolar sacs.

- Friedländer p. a form of p. caused by infection with Klebsiella pneumoniae (Friedländer bacillus), characteristically severe and lobar in distribution.

- Friedländer bacillus p. p. caused by Klebsiella pneumoniae, the Friedländer bacillus.

- gangrenous p. gangrene of the lungs.

- giant cell p. a rare complication of measles, with the postmortem finding of multinucleated giant cells lining alveoli. SYN: Hecht p., interstitial p..

- Hecht p. SYN: giant cell p..

- hospital-acquired p. p. in a patient in a hospital, or hospital-like setting, such as a rehabilitation facility. Often caused by Gram-negative or staphylococcal organisms. SYN: nosocomial p..

- hypostatic p. p. resulting from infection developing in the dependent portions of the lungs due to decreased ventilation of those areas, with resulting failure to drain bronchial secretions; occurs primarily in the aged or those debilitated by disease who lie in the same position for long periods.

- influenza p. p. complicating influenza.

- influenzal virus p. serious, often fatal form of p. caused by a virus of the influenzal type; occurs in epidemics and pandemics.

- p. interlobularis purulenta p. in which the lobules of the lung are separated by collections of purulent exudate. SYN: p. dissecans.

- interstitial p. SYN: giant cell p..

- interstitial plasma cell p. SYN: Pneumocystis carinii p..

- intrauterine p. fetal p. contracted in utero and manifesting itself in the early neonatal period.

- lipid p., lipoid p. pulmonary condition marked by inflammatory and fibrotic changes in the lungs due to the inhalation of various oily or fatty substances, particularly liquid petrolatum, or resulting from accumulation in the lungs of endogenous lipid material, either cholesterol from obstructive pneumonitis or following fracture of a bone; phagocytes containing lipid are usually present. SYN: oil p..

- lobar p. p. affecting one or more lobes, or part of a lobe, of the lung in which the consolidation is virtually homogeneous; often due to infection by Streptococcus pneumoniae; sputum is scanty and usually of a rusty tint from altered blood.

- lymphocytic interstitial p. (LIP) SYN: lymphocytic interstitial pneumonitis.

- lymphoid interstitial p. (LIP) SYN: lymphocytic interstitial pneumonitis.

- p. malleosa (ma-le′o-sa) p. associated with glanders.

- metastatic p. a purulent inflammation in the lungs due to infected emboli.

- migratory p. a form of p. in which successive areas of the lung are affected; may occur in bronchopulmonary aspergillosis. SYN: wandering p..

- nosocomial p. SYN: hospital-acquired p..

- obstructive p. infection of lung resulting from obstruction of airway, by narrowing resulting from previous disease process, persistent bronchospasm, or thick secretions or by aspiration of a foreign body.

- oil p. SYN: lipid p..

- Pittsburgh p. a variant of Legionnaires disease caused by Legionella micdadei.

- plague p. SYN: pneumonic plague.

- pleuritic p. p. associated with inflammation of the overlying pleura. SYN: pneumonopleuritis.

- Pneumocystis carinii p. (PCP) p. resulting from infection with Pneumocystis carinii, frequently seen in the immunologically compromised, such as persons with AIDS, or steroid-treated individuals, the elderly, or premature or debilitated babies during their first 3 months. In AIDS patients the tissue damage is usually restricted to the pulmonary parenchyma, whereas in the infantile form of the disease the alveoli are filled with a honeycomb-like or foamy network of acidophilic material, apparently not fibrin and not stainable with silver, within which the organisms, individually or in aggregates, are enmeshed; throughout the alveolar walls and pulmonary septa there is a diffuse infiltration of mononuclear inflammatory cells, chiefly plasma cells and macrophages, as well as a few lymphocytes. Patients may be only slightly febrile (or even afebrile), but are likely to be extremely weak, dyspneic, and cyanotic. This is a major cause of morbidity among patients with AIDS. SYN: interstitial plasma cell p., pneumocystosis.

- postobstructive p. p. occurring distally to a bronchial obstruction.

- primary atypical p. an older term referring to an acute systemic disease with involvement of the lungs, usually caused by Mycoplasma pneumoniae and marked by fever, cough, relatively few physical signs, and scattered densities on x-rays; usually associated with development of cold agglutinins and antibodies to the infectious agent.

- purulent p. p. caused by an organism that produces pus, implying that there can be destruction of lung tissue with permanent changes; usually sputum contains pus. Staphylococci, hemolytic streptococci, under streptococcus, and Friedländer bacillus are typical causes, as opposed to Streptococcus pneumoniae, which is rarely a cause of purulent p..

- rheumatic p. p. rarely occurring in severe acute rheumatic fever, even when the disease was common; consolidation occurs, the lungs being of a rubbery consistency, with fibrin exudate and small hemorrhages, as well as edema from left ventrical failure.

- septic p. SYN: suppurative p..

- staphylococcal p. p., usually caused by Staphylococcus aureus, usually commencing as a bronchopneumonia, and frequently leading to suppuration and destruction of lung tissue.

- streptococcal p. p. due to Streptococcus pyogenes.

- suppurative p. any p. associated with the formation of pus and destruction of pulmonary tissue; abscess formation may occur. SYN: septic p..

- terminal p. p. occurring in the course of some other disease near its fatal termination.

- tularemic p. tularemia with pulmonary lesions.

- typhoid p. p. complicating typhoid fever.

- unresolved p. p. in which the alveolar exudate persists and eventually undergoes fibrosis.

- uremic p. 1. SYN: uremic lung. 2. terminal infective p. occurring in a patient with uremia.

- usual interstitial p. of Liebow (UIP) a progressive inflammatory condition starting with diffuse alveolar damage and resulting in fibrosis and honeycombing over a variable time period; also a common feature of collagen-vascular diseases.

- wandering p. SYN: migratory p..

- woolsorter's p. SYN: pulmonary anthrax.

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pneu·mo·nia n(y)u̇-'mō-nyə n a disease of the lungs that is characterized esp. by inflammation and consolidation of lung tissue followed by resolution, is accompanied by fever, chills, cough, and difficulty in breathing, and is caused chiefly by infection see BRONCHOPNEUMONIA, LOBAR PNEUMONIA, PRIMARY ATYPICAL PNEUMONIA

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n.

inflammation of the lung caused by bacteria, in which the air sacs (alveolitis) become filled with inflammatory cells and the lung becomes solid (see consolidation). The symptoms include those of any infection (fever, malaise, headaches, etc.), together with cough and chest pain. Pneumonias may be classified in different ways.

(1) According to the X-ray appearance. Lobar pneumonia affects whole lobes and is usually caused by Streptococcus pneumoniae, while lobular pneumonia refers to multiple patchy shadows in a localized or segmental area. When these multiple shadows are widespread, the term bronchopneumonia is used. In bronchopneumonia, the infection starts in a number of small bronchi and spreads in a patchy manner into the alveoli.

(2) According to the infecting organism. The most common organism is Streptococcus pneumoniae, but Haemophilus influenzae, Staphylococcus aureus, Legionella pneumophila, and Mycoplasma pneumoniae (among others) may all be responsible for the infection. See also atypical pneumonia, viral pneumonia.

(3) According to the clinical and environmental circumstances under which the pneumonia is acquired. These infections are divided into community-acquired pneumonia, hospital-acquired (nosocomial) pneumonia, and pneumonias occurring in immunocompromised subjects (including those with AIDS). The organisms responsible for community-acquired pneumonia are totally different from those in the other groups.

Appropriate antibiotic therapy, based on the clinical situation and on microbiological studies, will result in complete recovery in the majority of patients.

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pneu·mo·nia (noo-mōnґyə) [Gr. pneumōnia] inflammation of the lungs with consolidation. Human pneumonias are most often categorized according to causative organism (such as amebic p., bacterial p., pneumocystis p., primary atypical p., and viral p.) or location (such as apical p., bronchial p., and lobar p.). See also pneumonitis.