Valvular disease
A. Generally, there are three types:
1. Stenosis—fibrotic, stiff, and thickened valves, resulting in reduced blood flow through the valve.

2. Regurgitation or valvular insufficiency— valves are unable to close completely, allowing blood to regurgitate.

3. Prolapse—“floppy” valves; may occur with or without regurgitation. The most common valvular defect.

DIPHTHERIA

An acute, contagious disease caused by Corynebacterium diphtheriae, characterized by the formation of a fibrinous pseudomembrane, usually on the respiratory mucosa, and by myocardial and neural tissue damage secondary to an exotoxin.

Cutaneous diphtheria (infection of the skin) can occur when any disruption of the integument is colonized by C. diphtheriae. Lacerations, abrasions, ulcers, burns, and other wounds are potential reservoirs of the organism. Skin carriage of C. diphtheriae is also a silent reservoir of infection.

Pathology

C. diphtheriae may produce exotoxins lethal to the adjacent host cells. Occasionally, the primary site is the skin or mucosa elsewhere. The exotoxin, carried by the blood, also damages cells in distant organs, creating pathologic lesions in the respiratory passages, oropharynx, myocardium, nervous system, and kidneys.

The myocardium may show fatty degeneration or fibrosis. Degenerative changes in cranial or peripheral nerves occur chiefly in the motor fibers

In severe cases, anterior horn cells and anterior and posterior nerve roots may show damage proportional to the duration of infection before antitoxin is given. The kidneys may show a reversible interstitial nephritis with extensive cellular infiltration.

The diphtheria bacillus first destroys a layer of superficial epithelium, usually in patches, and the resulting exudate coagulates to form a grayish pseudomembrane containing bacteria, fibrin, leukocytes, and necrotic epithelial cells. However, the areas of bacterial multiplication and toxin absorption are wider and deeper than indicated by the size of the membrane formed in the wake of the spreading infection.

Pathology

The branch of medicine dealing with the essential nature of disease, especially changes in body tissues aorgans that cause or are caused by disease. Pathology is the structural and functional manifestations of disease.

Anatomic pathology  the anatomical study of changes in the function, structure, or appearance of organs or tissues,including postmortem examinations and the study of biopsy specimens.

Cellular pathology  - Cytopathology is a diagnostic technique that examines cells from various body sites to determine the cause or the nature of disease.

Clinical pathology  pathology applied to the solution of clinical problems, especially the use of laboratory 

methods inclinical diagnosis.

Comparative pathology  that which considers human disease processes in comparison with those of other 

animals.

Oral pathology  that treating of conditions causing or resulting from morbid anatomic or functional changes in thestructures of the mouth.

Surgical pathology  the pathology of disease processes that are surgically accessible for diagnosis or treatment.

TOXOPLASMOSIS

Infection with Toxoplasma gondii, causing a spectrum of manifestations ranging from asymptomatic benign lymphadenopathy to life-threatening CNS disease, chorioretinitis, and mental retardation.

Symptomatic infections may present in several ways

Acute toxoplasmosis may mimic infectious mononucleosis with lymphadenopathy, fever, malaise, myalgia, hepatosplenomegaly, and pharyngitis. Atypical lymphocytosis, mild anemia, leukopenia, and slightly abnormal liver function tests are common. The syndrome may persist for weeks or months but is almost always self-limited.

A severe disseminated form characterized by pneumonitis, myocarditis, meningoencephalitis, polymyositis, diffuse maculopapular rash, high fevers, chills, and prostration. Acute fulminating disease is uncommon.

Congenital toxoplasmosis usually results from a primary (and often asymptomatic) acute infection acquired by the mother during pregnancy. The risk of transplacental infection increases from 15% to 30 to 60% for maternal infections acquired in the 1st, 2nd, or 3rd trimester of gestation, respectively

HYPERPLASIA
It is the increase in the size of an organ or tissue due to increase in the number of its constituent cells. This is seen in organs made up of labile and stable cells.

Causes
I. Increased demand:
- Bone marrow in hypoxia and haemolytic states.
- Thyroid gland in puberty

2. Persistant Trauma:
- Acanthosis of the epidermis in chronic inflammations and in warts.
- Hyperplasia of oral mucosa due tooth and denture trauma.
- Mucosa at the edges of a gastric ulcer.

3. Endocrine target organ:
- Pregnancy hyperplasia of breast.
- Prostatic hyperplasia.

4. Compensatory:

Hyperplasia of kidney when the other kidney has been removed.

5. Idiopathic:
Endocrine organs like thyroid, adrenals, pituitary etc. can undergo hyperplasia with no detectable stimulus. .
 

POLYCYTHEMIA

 It is an increase in number of RC per unit volume of blood (Hb more than 1.9.5 gms% and 18 gms% for women)
 
Causes :

True polycythemia.
- Idiopathic Polythemia vera.

- Secondary to :

    o    Hypoxia of high altitude , heart disease, chronic lung disease etc.
    o    Erythopoietin  oversecretion as in renal diseases , tumours of liver, kidney and adrenal etc.
    o    Compensatory in haemogIobinopathies
    
- Relative polycythemia due to reduction in plasma volume as in dehydration or in redistribution off fluids

Polycythemia vera: It is a myeloprolifeative disorder, usually terminating in myelosclerosis.

Features: are due to hypervolaemic circulation and tendency to tbrombosis and haemorrhage 

    -Headaches, dizziness and cardiovascular accidents.
    -Hypertension.
    -Peripheral vascular thrombosis.
    -GIT bleeding. retinal haemorrhage.
    -Gout.
    -Pruritus.

Blood Finding

-Increased Hb. PCV and RBC count.
-Leucocytosis with high alkaline  phosphatase.
-Platelets increased.

Marrow picture Hypercellular with  increase in precursors of all series 
Course Chronic course ending in myelosclerosis or acute  leukaemia.