Paget Disease (Osteitis Deformans) 

This unique bone disease is characterized by repetitive episodes of exaggerated, regional osteoclastic activity (osteolytic stage), followed by exuberant bone formation (mixed osteoclastic-osteoblastic stage), and finally by exhaustion of cellular activity (osteosclerotic stage). The net effect of this process is a gain in bone mass; however, the newly formed bone is disordered and lacks strength. Paget disease usually does not occur until mid-adulthood but becomes progressively more common thereafter. The pathognomonic histologic feature is a mosaic pattern of lamellar bone (likened to a jigsaw puzzle) due to prominent cement lines that haphazardly fuse units of lamellar bone. (Fig. 12-5) The axial skeleton and proximal femur are involved in the majority of cases. In patients with extensive disease, hypervascularity of the marrow spaces can result in high-output congestive heart failure. Cranial nerves impingement also occurs and can lead to head ache and auditory disturbances. Rarely Paget disease is complicated by bone sarcoma (usually osteogenic). 

Autopsy

Autopsy is examination of the dead body to identify the cause of death. This can be for forensic or clinical purposes.

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,

Smallpox (variola)
 - vesicles are well synchronized (same stage of development) and cover the skin and mucous membranes.
 - vesicles rupture and leave pock marks with permanent scarring.

 LUNG ABSCESS  Lung abscess is a localised area of necrosis of lung tissue with suppuration.

 It is of 2 types:

 - Primary lung abscess that develops in an otherwise normal lung. The commonest cause is aspiration of infected material.

 - Secondary lung abscess that develops as a complication of some other disease of the lung or from another site

ETIOPATHOGENESIS.

 The microorganisms commonly isolated from the lungs in lung abscess are streptococci, staphylococci and various gram-negative organisms. These are introduced into the lungs from one of the following mechanisms:

 1.   Aspiration of infected foreign material.

 2. Preceding bacterial infection.

 3.  Bronchial obstruction.

 4. Septic embolism.

 5. Miscellaneous (i) Infection in pulmonary infarcts, (ii) Amoebic abscesses, (iii) Trauma to the lungs. (iv) Direct extension from a suppurative focus.

Abscesses may be of variable size from a few millimeters to large cavities, 5 to 6 cm in diameter. The cavity often contains exudate. An acute lung abscess is initially surrounded by acute pneumonia and has poorly-defined ragged wall. With passage of time, the abscess becomes chronic and develops fibrous wall.

Microscopic Examination

The characteristic feature is the destruction of lung parenchyma with suppurative exudate in the lung cavity. The cavity is initially surrounded by acute inflammation in the wall but later there is replacement by exudate of lymphocytes, plasma cells and macrophages. In more chronic cases, there is considerable fibroblastic proliferation forming a fibrocollagenic wall.

Megaloblastic anaemia

Metabolism: B12(cyanocobalamin) is a coenzyme in DNA synthesis and for maintenance of nervous system. Daily requirement 2 micro grams. Absorption in terminal ileum in the presence gastric intrinsic factor. It is stored in liver mainly-

Folic acid (Pteroylglutamic acid) is needed for DNA synthesis.. Daily requirement 100 micro grams. Absorption in duodenum  and jejunum

Causes of deficiency .-

- Nutritional deficiency-
- Malabsorption syndrome.
- Pernicious anaemia (B12).
- Gastrectomy (B12).
- Fish tapeworm infestation (B12).
- Pregnancy and puerperium (Folic acid mainly).
- Myeloproliferative disorders (Folic acid).
- Malignancies (Folic acid).
- Drug induced (Folic-acid)

Features:

(i) Megaloblastic anaemia.
(ii) Glossitis.
(iii) Subacute combined degeneration (in B12deficiency).

Blood picture :

- Macrocytic normochromic anaemia.
- Anisocytosis and poikilocytosis with Howell-Jolly bodies and  basophilic stippling.
- Occasional megalo blasts may be-seen.
- Neutropenia with hypersegmented neutrophills and macropolycytes.
- Thrombocytopenia.
- Increased MVC and MCH with normal or decreased MCHC.

Bone marrow:

- Megaloblasts are seen. They are larger with a more open stippled chromatin. The nuclear maturation lags behind. the cytoplasmic maturation. Maturation arrest is seen (more of early forms).
- Immature cells of granulocyte series are also larger.
 -Giant stab forms (giant metamyelocytes).