Malignant Diseases of Skin
 
1. Bowen's disease refers to a carcinoma in situ on sun-exposed skin or on the vulva, glans a penis, or oral mucosa which has an association, in some cases, with a visceral malignancy.
2. Skin cancers associated with ultraviolet light damage include basal cell carcinoma, squamous cell carcinoma, and malignant melanoma.
3. A basal cell carcinoma is the MC malignant tumor of the skin and occurs on sunexposed, hair-bearing surfaces.
 - Locally aggressive, infiltrating cancers arising from the basal cell layer of the epidermis and infiltrate the underlying superficial dermis.
 - they do not metastasize
 - BCC are commonly located on the face on the inner aspect of the nose, around the orbit and the upper lip where they appear as raised nodules containing a central crater with a pearly-colored skin surface and vascular channels.
 - microscopically, they have cords of basophilic staining cells originating from the basal cell layer infiltrating the dermis.
 - they commonly recur if they are not totally excised, because they are frequently multifocal. 
- the basal cell nevus syndrome is an autosomal-dominant disorder characterized by the development of basal cell carcinomas early in life with associated abnormalities of bone, skin, nervous system, eyes, and reproductive system. 

CHRONIC INFLAMMATlON

When the inflammatory reaction instead of subsiding after the acute phase (or without entering an acute phase), persists as a smouldering lesion, it is called chronic inflammation. .

Characteristics

• Predominantly mononuclear response.
• Inflamation.and..repair going on simultaneously.
• Usually results in more prominent-scarring.

Causes:

Chronicity may be due to :

- Defective defence mechanisms.

- Persistence of injurious agent.

(a) Certain organisms resist phagocytosis and destruction e.g tubercle bacillus, fungi

(b) insoluble particulate matter e.g., crystals. fibres suture materials.

(c) Constants supply of causative agent as in autoimmune disease where body reacts against its own tissues.

- Defective healing.

Granulomatous inflammation

It is a type of chronic inflammation characterised by localised collections of histiocytes.

These cells are usually accompanied by lymphocytes, fibroblasts and giant cells also.

Granulomas are characteristically seen in diseases like tuberculosis. syphilis, leprosy, sarcoidosis, fungal infections etc. In some of these, the lesion is morphologically distinct  enough to point to the type of underlying disease. These are sometimes called' specific' granulomas. Granulomas can also be elicited by particulate, insoluble foreign material e.g. granuloma, suture granuloma, cholesterol granuloma (organising haemorrhages).

Pernicious anaemia 

The special features are:

• Due to intrinsic factor deficiency
• Gastric atrophy with histamine fast achlorhydria
• Genetic basis (racial distribution and blood group A).
• Seen with auto immune disorders.
• Antibodies to parietal cells and to intrinsic factors are seen

Streptococcal pharyngitis:

A disease of young people, enlarged lymphoid nodules and keratin plugs in the tonsillar pits is seen Complications include retro-pharyngeal abscess (quinsy)

Cellulitis of the deep tissues of the neck is Ludwig's angina

Scarlet fever ("scarlatina") is a strep throat caused by a streptococcus with the gene to make one of the erythrogenic toxins, Patients have a rash with PMNs

Streptococcal skin infections (Impetigo)

Erysipelas is a severe skin infection caused by group A strep; geographic of red, thickened, indurated areas of the skin are characteristic. Unlike staph infections, there is usually little or no tissue necrosis

Post-streptococcal hypersensitivity diseases include rheumatic fever, post-streptococcal glomerulonephritis, and some cases of erythema nodosum

Immunoglobulins. (Ig)

 These are made up of polypeptide chains. Each molecule is constituted by two heavy and two light chains, linked by disulfide (S-S) bonds. The h~ chains are of 5 types, with corresponding, types or  immunoglobulin. IgG (gamma), IgM (mu µ ), IgA(alpha α), IgD(delta ), IgE(epsilon)

Each of these can have light chains of either kappa (k) or lambda type.Each chain has a constant portion (constant for the subtype) land a variable portion (antigen specific).

Enzyme digestion can split the Ig molecule into.2 Fab (antibody binding) fragments and one Fc (crystallisable, complement binding ) fragment.

Characteristics of Immunoglobulin subclasses

I. Ig G:

(i) Predominant portion (80%) of Ig.

(ii) Molecular weight 150, 000

(iii) Sedimentation coefficient of 7S.

(iv) Crosses placental barrier and to extra cellular fluid.

• (v) Mostly neutralising effect. May be complement fixing.

(vi) Half life of 23 days.

2.IgM :

(i) Pentamer of Ig.

(ii) Molecular weight 900, 000

(iii) 19S.

(iv) More effective complement fixation and cells lysis

(v) Earliest to be produced in infections.

(vi) Does not cross placental barrier.

(vii) Halflife of 5 days.

3. Ig A :

• Secretory  antibody. Found in intestinal, respiratory secretions tears, saliva and urine also.
• Secreted  usually as a dinner with secretory piece.
• Mol. weight variable (160,000+)
• 7 S to 14 S.
• Half life of 6 days.

4.Ig D :

• Found in traces.
• 7 S.
• Does not cross placenta.

5. Ig E

• Normally not traceable
• 7-8 S (MoL weight 200,000)
• Cytophilic antibody, responsible for some hypersensitivity states,

Cardiac tamponade
A. Caused by accumulation of fluid in the pericardium. This severe condition can quickly impair ventricular filling and rapidly lead to  decreased cardiac output and death.

1. Signs and symptoms include:
a. Hypotension.
b. Jugular venous distention.
c. Distant heart sounds.