NEET MDS Lessons
General Pathology
Congenital heart defect
Congenital heart defects can be broadly categorised into two groups,
o acyanotic heart defects ('pink' babies) :
An acyanotic heart defect is any heart defect of a group of structural congenital heart defects, approximately 75% of all congenital heart defects.
It can be subdivided into two groups depending on whether there is shunting of the blood from the left vasculature to the right (left to right shunt) or no shunting at all.
Left to right shunting heart defects include
- ventricular septal defect or VSD (30% of all congenital heart defects),
- persistent ductus arteriosus or PDA,
- atrial septal defect or ASD,
- atrioventricular septal defect or AVSD.
Acyanotic heart defects without shunting include
- pulmonary stenosis, a narrowing of the pulmonary valve,
- aortic stenosis
- coarctation of the aorta.
cyanotic heart defects ('blue' babies).
obstructive heart defects
cyanotic heart defect is a group-type of congenital heart defect. These defects account for about 25% of all congenital heart defects. The patient appears blue, or cyanotic, due to deoxygenated blood in the systemic circulation. This occurs due to either a right to left or a bidirectional shunt, allowing significant proportions of the blood to bypass the pulmonary vascular bed; or lack of normal shunting, preventing oxygenated blood from exiting the cardiac-pulmonary system (as with transposition of the great arteries).
Defects in this group include
hypoplastic left heart syndrome,
tetralogy of Fallot,
transposition of the great arteries,
tricuspid atresia,
pulmonary atresia,
persistent truncus arteriosus.
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.
Herpes zoster, or shingles
- represents reactivation of a latent varicella-zoster infection.
- virus lies dormant in sensory dorsal root ganglia and when activated involves the distribution (dermatome) of the sensory nerve with a painful vesicular eruption.
- trigeminal verve distribution → Ramsay Hunt syndrome
- may indicate the presence of advanced neoplastic disease or be a complication of chemotherapy.
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.
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.
Osteogenesis Imperfecta (OI) (Brittle bone diseases)
It is a group of hereditary disorders caused by gene mutations that eventuate in defective synthesis of and thus premature degradation of type I collagen. The fundamental abnormality in all forms of OI is too little bone, resulting in extreme susceptibility to fractures. The bones show marked cortical thinning and attenuation of trabeculae.
Extraskeletal manifestations also occur because type I collagen is a major component of extracellular matrix in other parts of the body. The classic finding of blue sclerae is attributable to decreased scleral collagen content; this causes a relative transparency that allows the underlying choroid to be seen. Hearing loss can be related to conduction defects in the middle and inner ear bones, and small misshapen teeth are a result of dentin deficiency
Agranulocytosis. Severe neutropenia with symptoms of infective lesions.
Drugs. are an important cause and the effect may be due to .
-Direct toxic effect.
-Hypersensitivity.
Some of the 'high risk drugs are.
-Amidopyrine.
-Antithyroid drugs.
-Chlorpromazine, mapazine.
-Antimetabolites and other drugs causing pancytopenia.
Bloodpicture: Neutropenia with toxic granules in neutrophils. Marrow shows decrease in granulocyte precursors with toxic granules in them.