Peutz-Jeghers syndrome
1. Lesions appear as small, melanotic, and freckle-like. They can be found on the skin, oral mucosa, lips, feet, and hands. 
2. May also present with intestinal polyps, which may develop into a gastrointestinal carcinoma. 
3. Genetic transmission: autosomal dominant.

Post viral (post hepatitic) cirrhosis (15-20%) 

Cause:- Viral hepatitis (mostly HBV or HCV) 
Acute hepatitis  → chronic hepatitis → cirrhosis.  

Pathology
Liver is shrunken.  Fatty change is absent (except with HCV). Cirrhosis is mixed.

M/E  :-
Hepatocytes-show degeneration, necrosis  as other types of cirrhosis. 
Fibrous septa   -They are thick and immature (more cellular and vascular).
- Irregular margins (piece meal necrosis).
- Heavy lymphocytic infiltrate.

Prognosis:- - More rapid course than alcoholic cirrhosis.Hepatocellular carcinoma is more liable to occur 
 

Histopathological techniques

Histopathological examination studies tissues under the microscope. During this study, the pathologist looks for abnormal structures in the tissue. Tissues for histopathological examination are obtained by biopsy. Biopsy is a tissue sample from a living person to identify the disease. Biopsy can be either incisional or excisional.

Once the tissue is removed from the patient, it has to be immediately fixed by putting it into adequate amount of 10% Formaldehyde (10% formalin) before sending it to the pathologist.

The purpose of fixation is:

1. to prevent autolysis and bacterial decomposition and putrefaction

2. to coagulate the tissue to prevent loss of easily diffusible substances

3. to fortify the tissue against the deleterious effects of the various stages in the preparation of sections and tissue processing.

 4. to leave the tissues in a condition which facilitates differential staining with dyes and other reagents.

Psoriasis
1. Characterized by skin lesions that appear as scaly, white plaques.
2. Caused by rapid proliferation of the epidermis.
3. Autoimmune pathogenesis; exact mechanism is unclear.

Metastatic Tumors 

These are the most common malignant tumor of bone. Certain tumors exhibit a distinct skeletal prediliction. In adults more than 75% of skeletal metastases originate from cancers of the prostate, breast, kidney, and lung. In children, neuroblastoma, Wilms' tumor, osteosarcoma, Ewing sarcoma, and rhabdomyosarcoma are the common sources of bony metastases. Most metastases involve the axial skeleton (vertebral column, pelvis, ribs, skull, sternum), proximal femur, and humerus. The radiologic appearance of metastases can be purely osteolytic, purely osteoblastic, or mixed osteolytic-osteoblastic (majority of cases). In lytic lesions (e.g., kidney& lung), the metastatic cells secrete substances such as prostaglandins, interleukins, etc. that stimulate osteoclastic bone resorption; the tumor cells themselves do not directly resorb bone. Similarly, metastases that elicit a blastic response (e.g., prostate adenocarcinoma) do so by stimulating osteoblastic bone formation.

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,