NEET MDS Lessons
General Pathology
STOMACH
Congenital malformations
1. Pyloric stenosis
Clinical features. Projectile vomiting 3-4 weeks after birth associated with a palpable "olive" mass in the epigastric region is observed.
Pathology shows hypertrophy of the muscularis of the pylorus and failure to relax.
2. Diaphragmatic hernias are due to weakness in or absence of parts of the diaphragm, allowing herniation of the abdominal contents into the thorax.
Inflammation
1. Acute gastritis (erosive)
Etiology. Alcohol, aspirin and other NSAIDs, smoking, shock, steroids, and uremia may all cause disruption of the mucosal barrier, leading to inflammation.
Clinical features. Patients experience heartburn, epigastric pain, nausea, vomiting, hematemesis, and even melena.
2. Chronic gastritis (nonerosive) may lead to atrophic mucosa with lymphocytic infiltration.
Types
(1) Fundal (Type A) gastritis is often autoimmune in origin. It is the type associated with pernicious anemia and, therefore, achlorhydria and intrinsic factor deficiency.
(2) Antral (Type B) gastritis is most commonly caused by Helicobacter pylori and is the most common form of chronic gastritis in the U.S. H. pylori is also responsible for proximal duodenitis in regions of gastric metaplasia.
Clinical features. The patient may be asymptomatic or suffer epigastric pain, nausea, vomiting, and bleeding. Gastritis may predispose to peptic ulcer disease, probably related to H. pylori infection.
3. Peptic ulcers
Peptic ulcers are usually chronic, isolated ulcers observed in areas bathed by pepsin and HCI; they are the result of mucosal breakdown
Common locations are the proximal duodenum, the stomach, and the esophagus, often in areas of Barrett's esophagus.
Etiology. There are several important etiologic factors.
Duodenal ulcers occur predominantly in patients with excess acid secretion, while gastric ulcers usually occur in patients with lower than average acid secretion.
Other predisposing conditions include smoking, cirrhosis, pancreatitis, hyperparathyroidism, and H. pylori infection. Aspirin, steroids, and NSAlDs are known to be assoicated with peptic ulcer disease. Next to H. pylori colonization, aspirin or NSAID ingestion is the most common cause of peptic ulcer.
Clinical features. Patients experience episodic epigastric pain. Duodenal and most gastric ulcers are relieved by food or antacids. Approximately one-fifth of gastric ulcer patients get no relief from eating or experience pain again within 30 minutes.
Pathology. Benign peptic ulcers are well-circumscribed lesions with a loss of the mucosa, underlying scarring, and sharp walls.
Complications include hemorrhage, perforation, obstruction, and pain. Duodenal ulcers do not become malignant .Gastric ulcers do so only rarely; those found to be ma1ignant likely originated as a cancer that ulcerated.
Diagnosis is made by upper gastrointestinal Series , endoscopy, and biopsy to rule out malignancy or to demonstrate the presence of H. pylori.
4. Stress ulcers
are superficial mucosal ulcers of the stomach or duodenum or both. Stress may be induced by burns, sepsis shock, trauma, or increased intracranial pressure.
Tumors
1. Benign
a. Leiomyoma, often multiple, is the most common benign neoplasm of the stomach. Clinical features include bleeding, pain, and iron deficiency anemia.
b. Gastric polyps are due to proliferation of the mucosal epithelium.
2. Malignant tumors
a. Carcinoma
Etiology. Primary factors include genetic predisposition and diet; other factors include hypochlorhydria, pernicious anemia, atrophic gastritis, adenomatous polyps, and exposure to nitrosamines. H. pylori are also implicated.
Clinical features. Stomach cancer is usually asymptomatic until late, then presents with anorexia, weight loss, anemia, epigastric pain, and melena. Virchow's node is a common site of metastasis.
Pathology. Symptomatic late gastric carcinoma may be expanding or infiltrative. In both cases the prognosis is poor (approximately 10% 5-year survival), and metastases are frequently present at the time of diagnosis.
Adenocarcinomas are most common.
b. Gastrointestinal lymphomas may be primary In the gastrointestinal tract as solitary masses.
c. Sarcoma is a rare, large, ulcerating mass that extends into the lumen.
d. Metastatic carcinoma. Krukenberg's tumor is an ovaria metastasis from a gastric carcinoma.
e. Kaposi's sarcoma. The stomach is the most commonly involved GI organ in Kaposi's sarcoma. It primarily occurs in homosexual men, appearing as hemorrhagic polypoid, umbilicated nodular lesions, typically in a submucosal location. It rarely causes symptoms
Bronchitis
Bronchitis is an obstructive pulmonary disease characterized by inflammation of the bronchi of the lungs
Signs and symptoms
persistent cough that produces sputum
shortness of breath (dyspnea) on exertion
hypercapnia
insufficient oxygenation of the blood hypoxemia leading to cynosis
Severe chronic bronchitis will commonly lead to cor pulmonale and heart failure.
Pathology
an increase in the number of goblet cells with mucus blocking the airway clusters of pigmented alveolar macrophages
the presence of inflammatory cells (e.g. neutrophils) scarring (fibrosis) of the walls of the bronchioles
Diagnosis
- decreased intensity of breath sounds (rhonchi) and extended expiration.
- a sputum culture has pathogenic microorganisms
- a chest x-ray that reveals hyperinflation and increased bronchovascular markings
- a pulmonary function test that shows an increase in the lung's residual volume and a decreased vital capacity
Pathophysiology
- The initiating event in developing bronchitis appears to be chronic irritation due to inhalation of certain chemicals
- earliest clinical feature of bronchitis is increased secretion of mucus by submucousal glands of the trachea and bronchi
- Damage caused by irritation of the airways leads to inflammation and infiltration of the lung tissue by neutrophils
- The neutrophils release substances that promote mucousal hypersecretion
- As bronchitis persists to become chronic bronchitis, a substantial increase in the number of goblet cells in the small airways is seen
- The role of infection in the pathogenesis of chronic bronchitis appears to be secondary.
Treatment
Quit smoking, Oxygen therapy, bronchodilator drugs
Prognosis
Pulmonary hypertension, cor pulmonale, and chronic respiratory failure are possible complications of chronic bronchitis
In severe chronic bronchitis is poor
Summary
Hepatitis A → ssRNA → Picornavirus → Oral–anal
Hepatitis B → dsDNA → Hepadnavirus → Sexual contact , Blood (needles), Perinatal
Hepatitis C → ssRNA → Flavivirus → Sexual contact , Blood (needles)
Hepatitis D → ssRNA → Deltavirus → Sexual contact, Blood (needles)
Hepatitis E → ssRNA → Calicivirus → Oral–anal
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).
POLYCYTHEMIA
It is an increase in number of RC per unit volume of blood (Hb more than 1.9.5 gms% and 18 gms% for women)
Causes :
True polycythemia.
- Idiopathic Polythemia vera.
- Secondary to :
o Hypoxia of high altitude , heart disease, chronic lung disease etc.
o Erythopoietin oversecretion as in renal diseases , tumours of liver, kidney and adrenal etc.
o Compensatory in haemogIobinopathies
- Relative polycythemia due to reduction in plasma volume as in dehydration or in redistribution off fluids
Polycythemia vera: It is a myeloprolifeative disorder, usually terminating in myelosclerosis.
Features: are due to hypervolaemic circulation and tendency to tbrombosis and haemorrhage
-Headaches, dizziness and cardiovascular accidents.
-Hypertension.
-Peripheral vascular thrombosis.
-GIT bleeding. retinal haemorrhage.
-Gout.
-Pruritus.
Blood Finding
-Increased Hb. PCV and RBC count.
-Leucocytosis with high alkaline phosphatase.
-Platelets increased.
Marrow picture Hypercellular with increase in precursors of all series
Course Chronic course ending in myelosclerosis or acute leukaemia.
Joint pathology
1. Rheumatoid arthritis
a. Cause is autoimmune in nature.
b. More common in women aged 20 to 50.
c. Characterized by inflammation of the synovial membrane. Granulation tissue, known as pannus, will form in the synovium and expand over the articular cartilage. This causes the destruction of the underlying cartilage and results in fibrotic changes and ankylosis.
Scarring, contracture, and deformity of the joints may occur.
d. Clinical symptoms include swollen joints. It can affect any joint in the body.
2. Osteoarthritis
a. Most common arthritis.
b. Cause is unknown.
c. Higher incidence in women, usually after age 50.
d. Characterized by degeneration of the articular cartilage and the formation of osteophytes (bony spurs) at the margins of affected areas.
Clinical signs and symptoms include:
(1) Stiff and painful joints affecting joints in the hand (phalangeal joints) and weight-bearing joints.
(2) Heberden’s nodes—nodules at the distal interphalangeal joint.
(3) Bocard’s nodes—nodules at the proximal interphalangeal joint.
Leukaemias
Uncontrolled proliferation of leukocyte precursors (may be with associated red cell and platelet series proliferation).
Factors which may playa causal role are.
- Viral
- Radiation.
- Genetic.
Classification
1. Acule leukaemia:
a. Lymphocytic (lymphoblastic).
b. Myelocytic and promyelocytic (myeloblastic).
c. Monocytic.
d. Myelomonocytic.
e. Undifferentiated (Stem cell).
2. Chronic leukaemia:
a. Lymphocytic
b. Myelocytic
3. Miscellaneous:
a. Erythroleukaemia (De Guglielmo's disease).
b. Eosinophilic leukaemia.
c. Megakaryocytic leukaemia.