Sickle Cell Disease

Sickle cell anemia is a autosomal recessive genetic disorder. It affects the BETA GLOBIN gene on the CHROMOSOME 16. In sickle cell anemia, the hemoglobin abnormality consists of a point mutation in the beta chain gene for hemoglobin; the resulting abnormal gene product is denoted HbS. If you are heterozygous for the HbS gene you will have what is called sickle trait, which is asymptomatic .

 If you are homozygous for the HbS gene  you will get sickle cell disease, which is symptomatic in most patients.
 The problem with HbS is that as it releases oxygen, it polymerizes and aggregates with other HbS molecules, making the red cell stiff and distorted. These distorted, sickle-shaped red cells are fragile so the patient can end up with a hemolytic anemia.
This can occur as pure disease (homozygous) or trait (heterozygous) or with other haemoglobinopathies. It is common. in Negroes. It is due to Hb-s  which is much less soluble than Hb-A  hence deoxygenation insoluble form  sickling of RBC.

This causes:
•    Removal by RE system. 
•    Blockage of microvessels causing  ischaemia.
 

Cells Of  The Exudate

Granulocytes (Neutrophils, eosinophils, and basophils)

Monocytes (and tissue macrophages)

Lymphocytes

Neutrophils (polymorphs).

Characteristics

(1) Cell of acute inflammation.

(2) Actively motile.

(3) Phagocytic.

(4) Respond to chemotactic agents like.

Complement products.

Bacterial products.

Tissue breakdown

Lysosomal enzymes of other polymorphs

Functions

(1) Phagocytosis and intracellular digestion of bacteria.

(2) Exocytosis of lysosomal enzymes to digest dead tissue as the first step in the process of repair.

Eosinophils

Characteristics

(I) Cell of allergjc and immunologic inflammation.

(2) Motile and phagocytic but less so than a neutrophil.

(3) Response to chemotaxis similar to neutrophil. In addition, it is also responsive to antigens and antigen-antibody complexes.

(4) Steroids cause depletion of eosinophils.

Functions

(1) Contain most of the lysosomal enzymes that polymorphs have

(2) control of Histamine release and degradation in inflammation

Basophils (and mast cells)

Characteristics

(1) Contain coarse metachromatic granules.

(2) Contain, histamine and proteolytic enzymes

Functions

Histamine: release which causes some of the changes of inflammation and allergic

reactions. .

Monocytes .

Blood monocytes form a component of. the mononuclear phagocytic system (MPS), the other being tissue macrophages The tissue macrophages may be :

(a) Fixed phagocytic. cells:

• Kuffer cell of liver.
• Sinusoidal lining cells of spleen and lymph nodes.
• Pleural and peritoneal macrophages
• Alveolar macrophages.
• Microglial cells.

(b) Wandering macrophages or tissue histiocytes.

The tissue histiocytes are derived from blood monocytes.

Characteristics

.(1)Seen in inflammation of some duration, as they -outlive polymorphs.

(2) Actively phagocytic and motile.

(3) Fuse readily to from giant cells in certain situations.

Function

(1) Phagocytosis.

(2) Lysosomal enzyme secretion.

(3) Site of synthesis of some components of complement.

(4) Antigen handling and processing before presenting it to the Immune  competent cell.

(5) Secretion of lysosyme and interferon.

Giant cells can be

(A) Physiological

Syncytiotrophoblast, megakatyocytes, striated muscle, osteoclast.

(B) Pathological:

Foreign body: in the presence of particulate foreign matter like talc, suture material etc. and in certain infections_e g fungal.

Langhan's type: a variant of foreign body giant cell seen in tuberculosis.

Touton type in lipid rich situations like Xanthomas, lipid granulomas etc.

(iv) Aschoff cell in rheumatic carditis.

(v) Tumour gjant cells e.g. Reid-Sternberg cell in Hodgkin's Lymphoma, giant cells in any malignancy.

Lymphocytes and Plasma cells

These are the small mononuclear cell comprising the immune system

They are less motile than_macrophages and  neutrophils and are seen in chronic inflammation and immune based diseases.

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. .
 

STREPTOCOCCAL INFECTIONS

Most streptococci are normal flora of oropharynx

Group A streptococci:  Str. pyogenes

Group B streptococci:  Str. agalactiae

Str. pneumoniae

Strep viridans group

Group D: Enterococcus (lately Strep. Fecalis and E. fecium), causes urinary tract infections,

Chemical Mediators In Inflammation

Can be classified as :

A. Neurogenic

Also called the Triple Response of Lewis. It involves neurogenic vasodilatation of arterioles due to antidromic axon reflex arc. The constituents of the response are:

1. arteriolar vasoconstriction followed by

2. arteriolar vasodilatation

3. swelling

B. Chemical

1. Amines: Histamine and 5 hydroxytryptamine. Released  from platelets and mast cells.

Actions: Immediate and short lived.

Dilatation of arterioles.

Increased capillary premeability.

Kinins: Bradykinin and kallidin These are present in inactive from and are  activated by kinin forming proteases

Actions:

Arteriolar dilatation.

Increased vascular permeability

Pain

Kinin forming proteases Plasmin and Kallikrein. Present as inactive precursors.

Cleavage products of complement C₃a und C₅a are called anaphylatoxins

Actions:

Histamine release from mast cells

Chemotaxis (also C₅₆₇ )

Enhance phagocytosis.

 Polymorph components

Cationic: proteins which cause

Increased permeability

Histamine release.

Chemotaxis of monocytes

Neutral proteases which:

Cleave C3 and C5 to active form

Convert Kininogen to Kinin

Increase permeability.

Acid proteases which liberate leucokinins

Slow reacting. substance of anaphylaxis: (SRS-A) is a lipid released from mast cell.

Action --Increases vascular permeability

Prostaglandins: E1 + E2 _.

Platelets are rich source

Action:

Platelets are a rich source.

Vasodilatation.

Increased permeability.

Pain.

VIII. Miscellaneous: like

Tissue lactic acid.

 Bacterial toxins.

Connective tissue diseases
Marfan’s syndrome
a. Genetic transmission: autosomal dominant.
b. Characterized by a defective microfibril glycoprotein, fibrillin.
c. Clinical findings include tall stature, joints that can be hyperextended, and cardiovascular defects, including mitral valve prolapse and dilation of the ascending aorta.

Ehlers-Danlos syndrome
a. Genetic transmission: autosomal dominant or recessive.
b. This group of diseases is characterized by defects in collagen.
c. Clinical findings include hypermobile joints and highly stretchable skin. The skin also bruises easily. Oral findings include Gorlin’s sign and possible temporomandibular joint (TMJ) subluxation. 
The oral mucosa may also appear more fragile and vulnerable to trauma.