NEET MDS Lessons
General Pathology
Anemia (Disorder of Hematopoietic System) - Probably the most common effect of nutritional deficiency. Any factor that decreases hematopoiesis can cause an anemia.
A. Iron deficiency - Widely recognized as the most important cause of anemia, It is indicated that ½ of all pregnant women and infants are affected, as are ~13% of all adult women.
1. Dietary factors - Availability of iron from different food sources and mixtures.
2. Malabsorption – One third of patients with inflammatory bowel disease (IBD) have recurrent anemia and 30% or more of patients who have had partial gastrectomy will develop iron deficiency anemia.
3. Blood loss - Menses, gastrointestinal bleeding
4. Increased demand - Pregnancy, growth in children.
5. Congenital - Atransferrinemia
6. Importance of multiple factors.
7. Pathophysiology - Initially iron is mobilized from reticuloendothelial stores and increased intestinal absorption occurs. Total iron stores are depleted, serum iron levels fall. In severe cases in peripheral blood, the red cells become smaller (microcytic) and their hemoglobin content is reduced (hypochromic).
B. Megaloblastic anemias- Characterized by the presence of abnormal WBCs and RBCs. In severe cases, megaloblasts (abnormal red cell precursors) may be present. These anemias are a consequence of disordered DNA synthesis.
1. Folate deficiency - Can be caused by:
a. Dietary deficiency
b. Malabsorption (celiac disease)
c. Increased demand (pregnancy & lactation)
d. Drugs - methotrexate, anticonvulsants, oral contraceptives, alcoholism.
e. Liver disease
2. Cobalamin (vitamin B12) deficiency - Almost always a secondary disorder that can be caused by:
a. Intrinsic factor deficiency (pernicious anemia due to autoimmune destruction of the gastric mucosa)
b. Malabsorption
3. Pyridoxine (vitamin B6) deficiency- most commonly associated with alcoholism.
C. Other factors known to be frequently associated with anemia would include protein-calorie malnutrition, vitamin C deficiency, and pyridoxine deficiency (usually associated with alcoholism).
D. Other anemias not particularly associated with nutritional disease would include hemolytic anemia
(decreased red cell life span) and aplastic anemia (failure of marrow to produce new cells).
Nephrosclerosis
Disease of the renal arteries.
Clinical manifestations:
(1) Benign (arterial) nephrosclerosis → Caused by the formation of atherosclerotic plaques in the renal artery. Results in narrowing of the arterioles.
(2) Malignant nephrosclerosis → Caused by malignant hypertension. Common signs of malignant hypertension include severe hypertension, retinal hemorrhages, and hypertrophy of the left ventricle. Results in inflammatory changes in the vascular walls, which may lead to rupture of the glomerular capillaries.
Microbiological examination
This is a method by which body fluids, excised tissue, etc. are examined by microscopical, cultural and serological techniques to identify micro-organisms Microbiological examination responsible for many diseases.
DYSPLASIA
It is disturbed growth or cells in regard to their size, shape arrangement. In its mild degrees it represents a reversible reaction to chronic inflammation whereas the most severe degrees warrant a labelling of intraepithelial neoplasia. Hence it includes a wide spectrum of changes ranging from a reversible disorientation to 'carcinoma-in-situ'.
Histologically it is characterized by:
o Basal cell hyperplasia.
o Variation in size and shape of cells.
o Disorderly maturation.
o Increased mitotic activity.
o Disorientation of arrangement of cells (loss of polarity)
Dysplasia is commonly seen in:
o Squamous epithelium of cervix.
o Bronchial epithelium in habitual smokers.
o Gastric and colonic mucosa in long standing inflammation
o Oral and vulval leucoplakia
Cytopathologic techniques
Cytopathology is the study of cells from various body sites to determine the cause or nature of disease.
Applications of cytopathology:
- Screening for the early detection of asymptomatic cancer
2. Diagnosis of symptomatic cancer
3. Surveillance of patients treated for cancer
Cytopathologic methods
There are different cytopathologic methods including:
1. Fine-needle aspiration cytology (FNAC) -In FNAC, cells are obtained by aspirating the diseased organ using a very thin needle under negative pressure.
Superficial organs (e.g. thyroid, breast, lymph nodes, skin and soft tissues) can be easily aspirated.
Deep organs, such as the lung, mediastinum, liver, pancreas, kidney, adrenal gland, and retroperitoneum are aspirated with guidance by fluoroscopy, ultrasound or CT scan.
- Exfoliative cytology
Refers to the examination of cells that are shed spontaneously into body fluids or secretions. Examples include sputum, cerebrospinal fluid, urine, effusions in body cavities (pleura, pericardium, peritoneum), nipple discharge and vaginal discharge.
- Abrasive cytology
Refers to methods by which cells are dislodged by various tools from body surfaces (skin, mucous membranes, and serous membranes). E.g. preparation of cervical smears with a spatula or a small brush to detect cancer of the uterine cervix at early stages.
Rheumatic fever
Before antibiotic therapy, this was the most common cause of valvular disease.
1. Usually preceded by a group A streptococci respiratory infection; for example, strep throat.
2. All three layers of the heart may be affected. The pathologic findings include Aschoff bodies, which are areas of focal necrosis surrounded by a dense inflammatory infiltration.
3. Most commonly affects the mitral valve, resulting in mitral valve stenosis, regurgitation, or both.
Erythema nodosum is the MCC of inflammation of subcutaneous fat (panniculitis).
- it may be associated with tuberculosis, leprosy, certain drugs (sulfonamides), and is commonly a harbinger of coccidioidomycosis and sarcoidosis.
- commonly presents on the lower extremities with exquisitely tender, raised erythematous plaques and nodules.
- self-limited disease.