Serdar Balcı

Pulmonary Infections

Serdar BALCI, MD

Innate defenses in lung

Entrapment in the mucous blanket

Removal by means of the mucociliary elevator

Phagocytosis by alveolar macrophages

Phagocytosis and killing by neutrophils recruited by macrophage factors

Serum complement may enter the alveoli and be activated by the alternative pathway to provide the opsonin C3b, which enhances phagocytosis

Draining lymph nodes initiate immune responses

Robbins Basic Pathology

Adaptive immunity

Robbins Basic Pathology

Predisposing factors for infection


Any infection in the lung

Acute, fulminant clinical disease

Chronic disease with a more protracted course

Inflammation types in Pneumonia

Acute bacterial pneumonias Bronchopneumonia

A patchy distribution of inflammation

Involves more than one lobe

Initial infection of the bronchi and bronchioles

Extension into the adjacent alveoli

Robbins Basic Pathology


Patchy consolidation around small bronchi and bronchioles

Autopsy Pathology: A Manual and Atlas

necrotizing bronchopneumonia confluent gray areas

Autopsy Pathology: A Manual and Atlas

Lobar pneumonia

Contiguous air spaces of part or all of a lobe

Homogeneously filled with an exudate

Visualized on radiographs as a lobar or segmental consolidation

Streptococcus pneumoniae 90%

Robbins Basic Pathology

Gray hepatization stage

Gray-brown, dry, and firm

Right middle and lower lobes in this case

Autopsy Pathology: A Manual and Atlas


Robbins Basic Pathology

Community-Acquired Acute Pneumonias


Infection follows a viral upper respiratory tract infection

S. pneumoniae most common cause

Streptococcus pneumoniae


Heavy, red, and boggy

Vascular congestion

Proteinaceous fluid, scattered neutrophils, and many bacteria in the alveoli

Within a few days red hepatization

Liver-like consistency

The alveolar spaces are packed with neutrophils, red cells, and fibrin

Lobar pneumonia in the stage of red hepatization, the entire right lower lobe is inflamed, hyperemic, and consolidated

Autopsy Pathology: A Manual and Atlas

Robbins Basic Pathology

Gray hepatization

Lung is dry, gray, and firm

Red cells are lysed, while the fibrinosuppurative exudate persists within the alveoli

Robbins Basic Pathology

Gross view of lobar pneumonia with gray hepatization

The lower lobe is uniformly consolidated

Robbins Basic Pathology

Robbins Basic Pathology

S. pneumoniae complications

Robbins Basic Pathology

Community-Acquired Atypical Pneumonias

Acute febrile respiratory disease

Patchy inflammatory changes in the lungs

Confined to the alveolar septa and pulmonary interstitium

Mycoplasma pneumoniae most common


Whole lobes bilaterally or unilaterally

Red-blue, congested

Inflammatory reaction is largely confined within the walls of the alveoli

Septa are widened and edematous

Mononuclear inflammatory infiltrate of lymphocytes, histiocytes, and, occasionally, plasma cells

Alveolar spaces in atypical pneumonias are remarkably free of cellular exudate

Viral pneumonia

Thickened alveolar walls infiltrated with lymphocytes and some plasma cells, spilling over into alveolar spaces.

Focal alveolar edema

Early fibrosis at upper right

Robbins Basic Pathology

Robbins Basic Pathology

Hospital-Acquired Pneumonias

Acquired in the course of a hospital stay

Severe underlying disease


Prolonged antibiotic regimens

Mechanical ventilation

Robbins Basic Pathology

Aspiration Pneumonia

Robbins Basic Pathology

Lung abscess

Necrotizing bronchopneumoni

Multiple abscess cavities

S. aureus

Autopsy Pathology: A Manual and Atlas

Lung abscess complications

Lung abscess

Robbins Basic Pathology

Chronic pneumonia

Histoplasmosis, Coccidioidomycosis, Blastomycosis

Endemic in the Ohio and central Mississippi River valleys

Warm, moist soil, growth of the mycelial form, which produces infectious spores

Robbins Basic Pathology

Disseminated coccidioidomycosis causing miliary-like lesions, diffuse alveolar damage, and cyst formation

Autopsy Pathology: A Manual and Atlas

C. Immitis

Thick-walled, nonbudding spherules, 20 to 60 µm in diameter, often filled with small endospores

Endemic in the southwestern and far western regions of the United States

Robbins Basic Pathology

B. dermatitidis : round to oval and larger than Histoplasma (5 to 25 µm in diameter); reproduce by characteristic broad-based budding

Robbins Basic Pathology

Robbins Basic Pathology

Robbins Basic Pathology

Pneumonia in the Immunocompromised Host



Gigantism of both the entire cell and its nucleus

Nucleus is an enlarged inclusion surrounded by a clear halo (“owl’s eye”)

Organizing diffuse alveolar damage in cytomegalovirus pneumonia

Autopsy Pathology: A Manual and Atlas

Patchy necrosis related to Herpes simplex virus pneumonia

Autopsy Pathology: A Manual and Atlas

Robbins Basic Pathology

P. jiroveci

Everyone exposed to Pneumocystis during the first few years of life

Most the infection remains latent

Reactivation in immunocompromised

Necrotizing and cavitating infection with Pneumocystis carinii in a child with congenital AIDS

Autopsy Pathology: A Manual and Atlas

“cotton candy” exudate

septa are thickened by edema and a minimal mononuclear infiltrate

Robbins Basic Pathology

__ intracystic bodies but without budding in alveolar exudate__

Robbins Basic Pathology


Robbins Basic Pathology


Invasive aspergillosis causing necrotizing pneumonia and diffuse alveolar damage

Autopsy Pathology: A Manual and Atlas

Robbins Basic Pathology

Robbins Basic Pathology


Rhizopus and Mucor

Nondistinctive, suppurative, sometimes granulomatous reaction with a predilection for invading blood vessel walls, causing vascular necrosis and infarction

Localized necrotizing infection related to zygomycosis (mucormycosis)

Autopsy Pathology: A Manual and Atlas


Acquired by inhalation from the soil or from bird droppings

Localizes in the lungs and then disseminates to other sites, particularly the meninges

Robbins Basic Pathology

Pulmonary Disease in HIV

Neoplastic lesions occur with increased frequency and must be excluded

Kaposi sarcoma

Non-Hodgkin lymphoma

Primary lung cancer