📖 General Pathology

Respiratory Viral Diseases

Respiratory viral infections cause acute local and systemic illnesses. The common cold, influenza, pharyngitis, laryngitis (including croup), and tracheobronchitis are common.

An acute, usually afebrile, viral infection of the respiratory tract, with inflammation in any or all airways, including the nose, paranasal sinuses, throat, larynx, and sometimes the trachea and bronchi.

Etiology and Epidemiology

Picornaviruses, especially rhinoviruses and certain echoviruses and coxsackieviruses, cause the common cold. About 30 to 50% of all colds are caused by one of the > 100 serotypes of rhinoviruses.

Symptoms and Signs

Clinical symptoms and signs are nonspecific.

After an incubation period of 24 to 72 h, onset is abrupt, with a burning sensation in the nose or throat, followed by sneezing, rhinorrhea, and malaise.

Characteristically, fever is not present, particularly with a rhinovirus or coronavirus. Pharyngitis usually develops early; laryngitis and tracheobronchitis vary by person and causative agent. Nasal secretions are watery and profuse during the first days, but become more mucoid and purulent.

Cough is usually mild but often lasts into the 2nd wk.

Parkinson’s disease
a. Characterized by the degeneration of neurons in the basal ganglia, specifically the substantia nigra and striatum.
b. Histologic findings in affected neurons include Lewy bodies.
c. Clinically, the disease affects involuntary and voluntary movements. Tremors are common. Symptoms include pin-rolling tremors, slowness of movements, muscular rigidity, and shuffling gait.

Growth and spread of tumours

Growth in excess of normal is a feature of all tumours but extension to tissue away from the site of origin is a feature of malignant tumours.

Modes of spread of malignant tumours

- local, invasion. This is a feature of all malignant tumors and  takes place along tissue spaces and facial planes
    o    Lymphatic spread. Most often seen in carcinomas. This can be in the form of 
    o    Lymphatic permeation:  Where the cells extend along the lymphatics as a  solid core 
    o    Lymphatic embolisation: Where a group of tumour cells break off and get carried to the draining mode

-Vascular spread :  This is a common and early mode of spread for sarcomas but certain carcinomas like renal cell carcinoma and chorio carcinoma have a predilection to early vascular spread.

Vascular spread is most often due .to invasion of venous channels and can be by permeation or embolisation.

Lungs, liver, bones and brain are the common sites for vascular metastasis but
different tumours have different organ preference for metastasis, e.g. : Bronchogenic carcinoma often spreads to liver and adrenals.

-Body cavities and natural passages
    o    Gastrointestinal carcinomas spread to ovaries (Krukenberg’s tomour)