NEET MDS Lessons
General Pathology
Chickenpox (varicella)
- primarily a childhood disease (70%)
- incubation period 14-16 days; highly contagious; infectious 2 days before the vesicles until the last one dries.
- present with generalized, intensely pruritic skin lesions starting as macules vesicles pustules (MVP-most valuable player) usually traveling centrifugally to the face and out to the extremities; unlike smallpox vesicles, chickenpox vesicles appear in varying stages of development as successive crops of lesions appear; intranuclear inclusions similar to HSV.
- pneumonia develops in 1/3 of adults; MCC death in chickenpox.
- association with Reye's syndrome if child takes aspirin.
Varicose Veins
- are abnormally dilated, tortuous veins produced by prolonged increase in intraluminal pressure and loss of vessel wall support.
- The superficial veins of the leg are typically involved
-venous pressures in these sites can be markedly elevated -> venous stasis and pedal edema (simple orthostatic edema)
-Some 10% to 20% of adult males and 25% to 33% of adult females develop lower extremity varicose veins
RISK FACTORS
-> obesity
-> Female gender
-> pregnancy.
-> familial tendency (premature varicosities results from imperfect venous wall development)
Morphology
- wall thinning
- intimal fibrosis in adjacent segments
- spotty medial calcifications (phlebosclerosis)
- Focal intraluminal thrombosis
- venous valve deformities (rolling and shortening)
COMPLICATIONS
- stasis, congestion, edema, pain, and thrombosis
- chronic varicose ulcers
- embolism is very rare.
Fulminant hepatitis
Fulminant hepatitis leads to submassive and massive hepatic necrosis.
a. Etiology. HAV, HBV, HCV, delta virus (HDV) superinfection, HEV, chloroform, carbon tetrachloride, isoniazid, halothane, and other drugs (acetaminophen overdose) all may cause fulminant hepatitis.
b. Clinical features include progressive hepatic dysfunction with a mortality of 25%-90%.
c. Pathology
(1) Grossly, one sees progressive shrinkage of the liver as the parenchyma is destroyed.
Primary vs. secondary disorders - Most nutritional disorders in developed countries are not due to simple dietary deficiencies but are rather a secondary manifestation of an underlying primary condition or disorder.
• Chronic alcoholism
• Pregnancy and lactation
• Renal dialysis
• Eating disorders
• Prolonged use of diuretics
• Malabsorption syndromes
• Neoplasms
• Food fads
• Vegans
• AIDS
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.
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).
Amyotrophic lateral sclerosis (Lou Gehrig’s disease)
a. Characterized by the rapid degeneration of motor neurons in the spinal cord and corticospinal tracts.
b. More common in men in their 50s.
c. Clinically, the disease results in rapidly progressive muscle atrophy due to denervation. Other symptoms include fasciculations, hyperreflexia, spasticity, and pathologic reflexes. Death usually occurs within a few years from onset, usually by respiratory failure or infection.