Pathogenesis (development of disease)
Pneumonia usually results from descending (ascending) infections, but it can also result from aspiration (entry of foreign bodies or fluid into the respiratory tract) and hematogenous (“caused by the blood“) dissemination. In this case, the pathogens usually have several virulence factors (characteristic of a microorganism that determines its pathogenic effect) that enable them to enter the lungs (e.g., inhibition of cilia movement/movement of ciliated hairs). Pneumonia often develops on the ground of impaired immune defense (immunodeficiency). Due to the inflammatory process, lung function is reduced, and a perfusion-ventilation mismatch occurs. Histologically (by fine tissue), four types can be distinguished:
- Bronchopneumonia (progressive form of pneumonia in which the inflammation affects the area surrounding bronchi in a focal form).
- Interstitial pneumonia (form of pneumonia, which does not affect the alveoli (alveoli), but the interstitium (intermediate tissue)).
- Lobar pneumonia (course form of pneumonia, in which the inflammation of the lung tissue affects entire lobes of the lung).
- Miliary pneumonia (course form of pneumonia, with many small infiltrates due to hematogenous pathogen spread and immune deficiency).
Pneumonia can be caused by the following pathogens or causes:
- Atypical pathogens – Chlamydia, Legionella, Mycoplasma, Rickettsia and others lead to atypical pneumonia.
- Bacteria – Coxiella burnetii, Branhamella catarrhalis, Bordetella pertussis, Brucella, Chlamydia pneumoniae, Escherichia coli (E. coli), Francisella tularensis, Haemophilus influenzae, Klebsiella pneumoniae, Legionella, Pneumococcus, Pseudomonas aeruginosa, Staphylococcus (Staphylococcus aureus).
- Viruses – adenoviruses, coronavirus, cytomegalovirus, Epstein-Barr virus (EBV), enteroviruses, Hanta virus, herpes virus type 6B, herpes simplex virus type 1 (HSV-1), herpes simplex virus (HSV) type 2, HIV, influenza A-B virus, LCM virus, measles virus, MERS coronavirus, parainfluenza virus, respiratory syncytial virus (RSV), rubella virus, varicella zoster virus (VZV).
- Fungi – Aspergillus, Blastomyces spp, Candida, Coccidioides, Histoplasma.
- Parasites – Leishmania, Pneumocystis carinii, Toxoplasma gondii.
- Radiatio (radiotherapy)
- Inhalation of gastric contents by aspiration
- Drugs – bleomycin, busulfan, nitrofurantoin and others.
- Metal fumes and dusts
- Irritant gases – e.g. chlorine gas, nitrous gases.
Etiology (causes)
Biographical causes
- Genetic burden
- Genetic disease
- Cystic fibrosis (ZF) – genetic disease with autosomal recessive inheritance characterized by the production of secretions in various organs to be tamed.
- Genetic disease
Behavioral causes
- Nutrition
- Malnutrition, undernutrition.
- Increased intake and increased serum levels of copper, cadmium, lead.
- See prevention with micronutrients
- Consumption of stimulants
- Alcohol
- Tobacco (smoking)
- Bedriddenness
- Aspiration – inhalation of e.g. gastric acid, food residues, foreign bodies.
Disease-related causes
- Allergies
- General immune deficiency – e.g., HIV infection, immunosuppression (including neutropenic patients after chemotherapy, after transplantation, and patients on chronic immunosuppressive therapy for systemic diseases).
- Chronic liver and kidney diseases
- Cardiovascular disease – acute heart failure with back up of blood in the pulmonary circulation (congestive pneumonia).
- Infectious diseases – whooping cough, measles, influenza (flu).
- Pulmonary embolisms
- Lung diseases – chronic obstructive pulmonary disease (COPD), emphysema, bronchiectasis (synonym: bronchiectasis), bronchitis.
- Poor general condition and underweight
- Obstruction of a bronchus – for example, due to bronchial carcinoma.
Medication
- Benzodiazepines
- In patients suffering from Alzheimer’s disease (+28%).
- In the group of sleep-inducing benzodiazepines: increase in pneumonia rate 2.4-fold ; in non-benzodiazepine sleep aids, the so-called Z-substances, and anxiety-relieving benzodiazepines: increase in pneumonia rate 1.6- and 1.5-fold, respectively.
- Glucocorticoids [aspergillosis.]
- Nitrofurantoin → eosinophilic pneumonia (as a side effect).
- Proton pump inhibitors (PPIs; acid blockers): 1.0% of subjects without PPI therapy and 2.4% of subjects with PPI therapy have an increased risk of community-acquired pneumonia (AEP; English CAP = community acquired pneumonia)
- Ustekinumab → “non-infectious” pneumonia.
- Cytostatic drugs
Environmental pollution – intoxications (poisonings).
- Air pollutants: particulate matter
More
- Wearing dentures while sleeping at night; 2.38-fold risk of pneumonia (compared with those who took dentures out of their mouths at night)
Nosocomial pneumonia (hospital-acquired pneumonia, HAP)
Risk factors for infections with multidrug-resistant pathogens (MRE).
