NEET MDS Lessons
General Pathology
Emphysema
Emphysema is a chronic lung disease. It is often caused by exposure to toxic chemicals or long-term exposure to tobacco smoke.
Signs and symptoms
loss of elasticity of the lung tissue
destruction of structures supporting the alveoli
destruction of capillaries feeding the alveoli
The result is that the small airways collapse during expiration, leading to an obstructive form of lung disease
Features are: shortness of breath on exertion
hyperventilation and an expanded chest.
As emphysema progresses, clubbing of the fingers may be observed, a feature of longstanding hypoxia.
Emphysema patients are sometimes referred to as "pink puffers". This is because emphysema sufferers may hyperventilate to maintain adequate blood oxygen levels. Hyperventilation explains why emphysema patients do not appear cyanotic as chronic bronchitis (another COPD disorder) sufferers often do; hence they are "pink" puffers (adequate oxygen levels in the blood) and not "blue" bloaters (cyanosis; inadequate oxygen in the blood).
Diagnosis
spirometry (lung function testing), including diffusion testing
X-rays, high resolution spiral chest CT-scan,
Bronchoscopy, blood tests, pulse oximetry and arterial blood gas sampling.
Pathophysiology :
Permanent destructive enlargement of the airspaces distal to the terminal bronchioles without obvious fibrosis
Oxygen is inhaled in normal breathing
When toxins such as smoke are breathed into the lungs, the particles are trapped by the hairs and cannot be exhaled, leading to a localised inflammatory response. Chemicals released during the inflammatory response (trypsin, elastase, etc.) are released and begin breaking down the walls of alveoli. This leads to fewer but larger alveoli, with a decreased surface area and a decreased ability to take up oxygen and loose carbon dioxide. The activity of another molecule called alpha 1-antitrypsin normally neutralizes the destructive action of one of these damaging molecules.
After a prolonged period, hyperventilation becomes inadequate to maintain high enough oxygen levels in the blood, and the body compensates by vasoconstricting appropriate vessels. This leads to pulmonary hypertension. This leads to enlargement and increased strain on the right side of the heart, which in turn leads to peripheral edema (swelling of the peripherals) as blood gets backed up in the systemic circulation, causing fluid to leave the circulatory system and accumulate in the tissues.
Emphysema occurs in a higher proportion in patient with decreased alpha 1-antitrypsin (A1AT) levels
Prognosis and treatment
Emphysema is an irreversible degenerative condition
Supportive treatmentis by supporting the breathing with anticholinergics, bronchodilators and (inhaled or oral) steroid medication, and supplemental oxygen as required
Lung volume reduction surgery (LVRS) can improve the quality of life for only selected patients.
A dermatofibroma is a benign tumor of the dermis, MC located on the lower extremity, where it has a nodular, pigmented appearance.
- composed of benign histiocytes.
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
ATROPHY
It is the acquired decrease in the size of an organ due to decrease in the size and/or number of its constituent cells.
Causes:
(1) Physiological
- Foetal involution.
o Branchial clefts.
o Ductus arterious.
- Involution of thymus and other lymphoid organs in childhood and adolescence.
- In adults:
o Post-partum uterus.
o Post-menopausal ovaries and uterus
o Post-lactational breast
o Thymus.
(2) Pathological:
- Generalised as in
o Ageing.
o Severe starvation and cachexia
- Localised :
o Disuse atropy of bone and muscle.
o Ischaemic atrophy as in arteriosclerotic kidney. .
o Pressure atrophy due to tumours and of kidney in hydronephrosis.
o Lack of trophic stimulus to endocrines and gonads.
Metastatic Tumors
These are the most common malignant tumor of bone. Certain tumors exhibit a distinct skeletal prediliction. In adults more than 75% of skeletal metastases originate from cancers of the prostate, breast, kidney, and lung. In children, neuroblastoma, Wilms' tumor, osteosarcoma, Ewing sarcoma, and rhabdomyosarcoma are the common sources of bony metastases. Most metastases involve the axial skeleton (vertebral column, pelvis, ribs, skull, sternum), proximal femur, and humerus. The radiologic appearance of metastases can be purely osteolytic, purely osteoblastic, or mixed osteolytic-osteoblastic (majority of cases). In lytic lesions (e.g., kidney& lung), the metastatic cells secrete substances such as prostaglandins, interleukins, etc. that stimulate osteoclastic bone resorption; the tumor cells themselves do not directly resorb bone. Similarly, metastases that elicit a blastic response (e.g., prostate adenocarcinoma) do so by stimulating osteoblastic bone formation.
Strep viridans
Mixed species, all causing α-hemolysis. All are protective normal flora which block adherence of other pathogens. Low virulence, but can cause some diseases:
Sub-acute endocarditis can damage heart valves.
Abscesses can form which are necrotizing. This is the primary cause of liver abscesses.
Dental caries are caused by Str. mutans. High virulence due to lactic acid production from glucose fermentation. This is why eating sugar rots teeth. Also have surface enzymes which deposit plaque.
Adrenocortical Hyperfunction (Hyperadrenalism)
Hypercortisolism (Cushing Syndrome) is caused by any condition that produces an elevation in glucocorticoid levels. The causes of this syndrome are
A. Exogenous through administration of exogenous glucocorticoids; the most common causeB. Endogenous
1. Hypothalamic-pituitary diseases causing hypersecretion of ACTH (Cushing disease)
2. Adrenocortical hyperplasia or neoplasia
3. Ectopic ACTH secretion by nonendocrine neoplasms (paraneoplastic)
Pathological features
- The main lesions of Cushing syndrome are found in the pituitary and adrenal glands.
- The most common change in the pituitary, results from high levels of endogenous or exogenous glucocorticoids, is termed Crooke hyaline change. In this condition, the normal granular, basophilic cytoplasm of the ACTH-producing cells in the anterior pituitary is replaced by homogeneous, lightly basophilic material. This is due to accumulation of intermediate keratin filaments in the cytoplasm.
- There is one of four changes in the adrenal glands, which depends on the cause.
1. Cortical atrophy
2. Diffuse hyperplasia
3. Nodular hyperplasia
4. Adenoma, rarely a carcinoma
1. In patients in whom the syndrome results from exogenous glucocorticoids, suppression of endogenous ACTH results in bilateral cortical atrophy, due to a lack of stimulation of the cortex by ACTH. In cases of endogenous hypercortisolism, in contrast, the adrenals either are hyperplastic or contain a cortical neoplasm.
2. In Diffuse hyperplasia the adrenal cortex is diffusely thickened and yellow, as a result of an increase in the size and number of lipid-rich cells in the zonae fasciculata and reticularis.
3. Nodular hyperplasia, which takes the form of bilateral, up to 2.0-cm, yellow nodules scattered throughout the cortex.
4. Primary adrenocortical neoplasms causing Cushing syndrome may be benign or malignant. The adrenocortical adenomas are yellow tumors surrounded by capsules, and most weigh < 30 gm .