Presentation1 Pneumonia

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Pulmonary Pathology

PNEUMONIA-(TOPIC OVERVIEW)

Is anInflammatoryCondition of thelung Affecting Primarily the microscopic Air Sacs Known asAlveoli

it is usually caused by airborne infection with virusesorbacteriaand less commonly other microorganisms, certain drugsand other conditions such as autoimmune diseases, also less common by Fungi and parasites.The term`pneumoniais sometimes more broadly applied to any condition resulting in Inflammationof the lungs; however, this inflammation is more accurately referred to aspneumonitis

Pneumonia can be classified base on the degree of damage/lesion caused:

Segmental / lobular pneumonia (it involves one segment of a lobe)B. Lobara (it involves an entire lobe, one/more lobes)C. Bronhopneumonia (uni/bilateral disseminated foci of pneumonia) D. Interstitial (it involves the interstitium- alveolar walls, peribronchial and perivascular space)

Bacterial PneumoniaBacteria are the most common cause ofcommnity-acquired pneumonia(CAP)(CAP), withStreptococcus pneumonia, Streptococcus Pneumoniaeisolated in nearly 50% of casesOther commonly isolated bacteria include:Haemophilus influenzain 20%,Chalamydophila pneumonia 13%, and Mycoplasma pneumoniae in 3% of cases;Staphyloccoccus aureus;Moraxella catarrhails; Legionella pnemophila and Gram-negative bacilliVIAL PNEUMONIAIn adults, viruses account for approximately a third[6] and in children for about 15% of pneumonia cases.[22] Commonly implicated agents include: rhinoviruses, coronaviruses,influenza virus, respiratory syncytial virus (RSV), adenovirus, and parainfluenza.[6][23] Herpes simplex virus rarely causes pneumonia,

Lobar pneumonia

Lobar pneumonia is a form of pneumonia that affects a large and continuous area of the lobe of a lung.It is one of the two anatomic, classifications of pneumonia.must commonly involving pneumococcusLobar pneumonia of the middle lobe

shows the location of the lungs and airways in the body. This figure also shows pneumonia affecting the lower lobe of the left lung.Lobar pneumoniaStagesLobar pneumonia usually has an acute progression. Classically, the disease has four stages:

Congestion in the first 24 hours: This stage is characterized histologically by vascular engorgement, intra-alveolar fluid, small numbers of neutrophils, often numerous bacteria. Grossly, the lung is heavy and hyperemic.(prehepatization)

Red hepatization or consolidation : Vascular congestion persists, with extravasation of red cells into

alveolar spaces, along with increased numbers of neutrophils and fibrin.This appearance has been likened to that of the liver, hence the term "hepatization".

Grey hepatization : Red cells disintegrate, with persistence of the neutrophils and fibrin. The alveoli still appear consolidated, but grossly the color is paler and the cut surface is drier.

Resolution (complete recovery):The exudate is digested by enzymatic activity, and cleared by macrophages or by cough mechanism

Lobar pneumonia, gross:The lower half of the specimen shows consolidation of an entire lobe.The picture is an example of the phase of Gray hepatization, whereby the inflammatory exudate is becoming organized and the gross appearance simulates that of the liver.

Lobar pneumonia (low power) (High Power)The alveolar spaces are diffusely filled by neutrophils and neutrophilic debris

Evolution: Pneumonia may be complicated through transition to abcess (hepatisation yellow), organization and fibrosis (carnification) or the occurrence of septic metastases frequently to the aortic valve.

Microscopy: It is found in the alveoli presence of fibrinous exudate partially lysed (homogeneous filling the alveoli and is giving to the lung parenchyma the liver-like consistency) and a significant amount of PMN granulocytes and macrophages in various stages of decay, mixed with desquamated pneumocytes and RBCs. The general appearance isthe leukocyte alveolitis :1.Alveolar septa are retained, 2.thickened by capillary congestion,and small bronchi 3.exudate containing serofibrinos debris mixed with PMNs.