NEET MDS Lessons
General Pathology
EMBOLISM
Definition: transportation of an abnormal mass of an abnormal mass of undissolved material from one part of circulation to another. The mass transported is called embolus.
Types
I .Thrombi and clots.
2. Gas or air.
3. Fat
4.Amniotic fluid.
5.Tumour
Thromboembolism
This is the commonest type of embolus and may be formed of the primary thrombus or more often of propagated clot region which is loosely attached.
Emboli from venous thrombi can result In impaction in the pulmonary arteries and result in sudden death.
Embolism from cardiac or arterial thrombi results in systemic embolism causing infraction and gangrene.
Gaseous
This occurs when gas is introduced into the circulation:
• Accidental opening of large veins during surgery.
• Mismanaged transfusion. .
As air is readily absorbed into blood only sudden introduction or large quantities of air produces effects
Caisson’s Disease bubbling of nitrogen from the blood during sudden decompression as seen during deep sea diving.
Fat Embolism
Causes
• Fractures especially of long bones and multiple
• Crush injuries.
Sites of impaction:
o Lungs.
o Systemic: causing -
→ petechial skin haemorrhages.
→ Embolism to brain leading to coma and death.
→ Conjunctival and retinal haemorrhages
Tumor Embolism.
Invasion of vascular channe1.s is a feature of malignant neoplasms and this leads to:
• Metastatic deposits,
• DlC
Biliary cirrhosis(16%)
It is due diffuse chronic cholestaisis (obstruction of the biliary flow) leading to damage and scarring all over the liver. Two types are known
1. Primary biliary cirrhosis and
2. Secondary biliary cirrhosis.
Primary biliary cirrhosis
It is destructive chronic inflammation of intrahepatic bile ductules and small ducts leading to micronodular cirrhosis.
-Typically affects middle aged women.
- Patients present with fatigue, pruritis and eventually, jaundice.
Cause:- Autoimmune. Patients have autoantibodies directed against mitochondrial enzymes (AMA).
Pathology:-
Liver is enlarged, dark green in color (cholestaisis). Cirrhosis is micronodular.
M/E :-
- Early, portal tracts show lymphocytes and plasma cell infiltrate the bile ducts and destroy them.
- Granulomatous inflammation surrounding the damaged and inflamed bile ducts is the hallmark of (PBC).
- Cholestatic changes such as bile ductular proliferation, periportal Mallory’s hyaline and increased copper in periportal hepatocytes.
- In the end stage disease, micro nodular cirrhosis occurs and the inflammatory changes subside
Secondary biliary cirrhosis:-
It is extra hepatic (surgical) cholestaisis due to prolonged extra hepatic major bile duct obstruction.
Causes - Obstruction of hepatic or common bile duct by:
- Congenital biliary atresia.
- Pressure by enlarged LN or tumor * Biliary stones.
- Carcinoma of the bile duct, ampulla of Vater or pancreatic head
Effects of obstruction:-
Complete obstruction leads to back pressure all over the biliary tract
- damage by inspessated bile
- inflammation and scarring.
Incomplete obstruction leads to acute suppurative cholangitis and cholangiolitis.
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.
Glomerulonephritis
Characterized by inflammation of the glomerulus.
Clinical manifestations:
Nephrotic syndrome (nephrosis) → Most often caused by glomerulonephritis.
Laboratory findings:
(i) Proteinuria (albuminuria) and lipiduria—proteins and lipids are present in urine.
(ii) Hypoalbuminemia—decreased serum albumin due to albuminuria.
(iii) Hyperlipidemia—especially an increase in plasma levels of low-density lipoproteins and cholesterol.
Symptoms
severe edema, resulting from a decrease in colloid osmotic pressure due to a decrease in serum albumin.
Nevus
1. Commonly known as moles.
2. A benign, pigmented tumor of melanocytes, found deep within connective tissue.
3. Types of skin nevi:
a. Junctional nevus—found in the epidermis.
It is the only type of nevus that may be considered to be premalignant.
b. Compound nevus—found in both the epidermis and underlying dermis.
c. Intraepidermal nevus—found in the dermis.
Alcoholic (nutritional, Laennec’s) cirrhosis
Pathology
Liver is at first enlarged (fatty change), then return to normal size and lastly, it becomes slightly reduced in size (1.2 kg or more).
- Cirrhosis is micronodular then macronodular then mixed.
M/E
Hepatocytes:- show fatty change that decreases progressively. Few hepatocytes show increased intracytoplasmic haemochromatosis.
b. Fibrous septa:- Regular margins between it and regenerating nodules.
-Moderate lymphocytic infiltrate.
– Slight bile ductular proliferation.
Prognosis:- It Progresses slowly over few years.
Bacterial endocarditis
Endocarditis is an infection of the endocardium of the heart, most often affecting the heart valves.
A. Acute endocarditis
1. Most commonly caused by Staphylococcus aureus.
2. It occurs most frequently in intravenous drug users, where it usually affects the tricuspid valve.
B. Subacute endocarditis
1. Most commonly caused by less virulent organisms, such as intraoral Streptococcus viridans that can be introduced systemically via dental procedures.
2. Pathogenesis: occurs when a thrombus or vegetation forms on a previously damaged or congenitally abnormal valve. These vegetations contain bacteria and inflammatory cells. Complications can arise if the thrombus embolizes, causing septic infarcts.
Other complications include valvular dysfunction or abscess formation.
3. Symptoms can remain hidden for months.
4. Valves affected (listed most to least common):
a. Mitral valve (most frequent).
b. Aortic valve.
c. Tricuspid (except in IV drug users, where the tricuspid valve is most often affected).