NEET MDS Lessons
General Pathology
Adult Respiratory Distress Syndrome
A constellation of pathologic and clinical findings initiated by diffuse injury to alveolar capillaries. This syndrome is associated with a multitude of clinical conditions which primarily damage the lung or secondarily as part of a systemic disorder.
Pathogenesis
There are many types of injuries which lead to the ultimate, common pathway, i.e., damage to the alveolar capillary unit. The initial injury most frequently affects the endothelium, less frequently the alveolar epithelium. Injury produces increased vascular permeability, edema, fibrin-exudation (hyaline membranes). Leukocytes (primarily neutrophils) plays a key role in endothelial damage.
Pathology
Heavy, red lungs showing congestion and edema. The alveoli contain fluid and are lined by hyaline membranes.
Pathophysiology
Severe respiratory insufficiency with dyspnea, cyanosis and hypoxemia refractory to oxygen therapy.
Valvular disease
A. Generally, there are three types:
1. Stenosis—fibrotic, stiff, and thickened valves, resulting in reduced blood flow through the valve.
2. Regurgitation or valvular insufficiency— valves are unable to close completely, allowing blood to regurgitate.
3. Prolapse—“floppy” valves; may occur with or without regurgitation. The most common valvular defect.
Keloids
1. Characterized by a progressively enlarging scar.
2. Caused by an abnormal accumulation of collagen at the site of injury.
3. More common in African-Americans.
Sickle Cell Disease
Sickle cell anemia is a autosomal recessive genetic disorder. It affects the BETA GLOBIN gene on the CHROMOSOME 16. In sickle cell anemia, the hemoglobin abnormality consists of a point mutation in the beta chain gene for hemoglobin; the resulting abnormal gene product is denoted HbS. If you are heterozygous for the HbS gene you will have what is called sickle trait, which is asymptomatic .
If you are homozygous for the HbS gene you will get sickle cell disease, which is symptomatic in most patients.
The problem with HbS is that as it releases oxygen, it polymerizes and aggregates with other HbS molecules, making the red cell stiff and distorted. These distorted, sickle-shaped red cells are fragile so the patient can end up with a hemolytic anemia.
This can occur as pure disease (homozygous) or trait (heterozygous) or with other haemoglobinopathies. It is common. in Negroes. It is due to Hb-s which is much less soluble than Hb-A hence deoxygenation insoluble form sickling of RBC.
This causes:
• Removal by RE system.
• Blockage of microvessels causing ischaemia.
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.
Blastomycosis (North American Blastomycosis; Gilchrist's Disease)
A disease caused by inhalation of mold conidia (spores) of Blastomyces dermatitidis, which convert to yeasts and invade the lungs, occasionally spreading hematogenously to the skin or focal sites in other tissues.
Pulmonary blastomycosis tends to occur as individual cases of progressive infection
Symptoms are nonspecific and may include a productive or dry hacking cough, chest pain, dyspnea, fever, chills, and drenching sweats. Pleural effusion occurs occasionally. Some patients have rapidly progressive infections, and adult respiratory distress syndrome may develop.
Glycogen storage diseases (glycogenoses)
1. Genetic transmission: autosomal recessive.
2. This group of diseases is characterized by a deficiency of a particular enzyme involved in either glycogen production or degradative pathways.
Diseases include:
on Gierke disease (type I)
(a) Deficient enzyme: glucose-6-phosphatase.
(b) Major organ affected by the buildup of glycogen: liver.
Pompe disease (type II)
(1) Deficient enzyme: α-glucosidase(acid maltase).
(2) Major organ affected by the buildup of glycogen: heart.
Cori disease (type III)
(1) Deficient enzyme: debranching enzyme (amylo-1,6-glucosidase).
(2) Organs affected by the buildup of glycogen: varies between the heart, liver, or skeletal muscle.
Brancher glycogenosis (type IV)
(1) Deficient enzyme: branching enzyme.
(2) Organs affected by the buildup of glycogen: liver, heart, skeletal muscle, and brain.
McArdle syndrome (type V)
(1) Deficient enzyme: muscle phosphorylase.
(2) Major organ affected by the buildup of glycogen: skeletal muscle.