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.
Parvoviruses
- smallest DNA virus
- erythema infectiosum (fifth disease) is characterized by a confluent rash usually beginning on the cheeks ("slapped face") which extends centripetally to involve the trunk; fever, malaise and respiratory problems; and arthralgias and joint swelling (50%).
other associations:
- aplastic anemia in patients with chronic hemolytic anemias (e.g., sickle cell disease, spherocytosis).
- repeated abortions associated with hydrops fetalis.
- pure RBC aplasia by involving the RBC precursors (no reticulocytes peripherally).
-chronic arthritis
Langerhans cell granulomatosis (histocytosis X)
a. A group of diseases that are caused by the proliferation of Langerhans’ cells (previously known as histocytes).
b. Most commonly causes bone lesions; however, other tissues can be affected.
c. Histologic findings include Langerhans’ cells containing Birbeck granules and eosinophils.
d. Three types:
(1) Letterer-Siwe disease—an acute, disseminated form that is fatal in infants.
(2) Hand-Schüller-Christian disease—a chronic, disseminated form that has a better prognosis than LettererSiwe disease. It usually presents
before the age of 5 and is characterized by a triad of symptoms:
(a) Bone lesions—found in skull, mandible (loose teeth).
(b) Exophthalmos.
(c) Diabetes insipidus.
(3) Eosinophilic granuloma of bone—a localized, least severe form of the three. Lesions may heal without treatment.
(a) Most commonly occurs in young adults.
(b) Lesions in the mandible may cause loose teeth.
ADRENOCORTICAL TUMORS
Functional adenomas are commonly associated with hyperaldosteronism and with Cushing syndrome, whereas a virilizing neoplasm is more likely to be a carcinoma. Determination of of the functional status of a tumor is based on clinical evaluation and measurement of the hormone or its metabolites. In other words, functional and nonfunctional adrenocortical neoplasms cannot be distinguished on the basis of morphologic features.
Patholgical features
Adrenocortical adenomas
- They are generally small, 1 to 2 cm in diameter.
- On cut surface, adenomas are usually yellow to yellow-brown due to presence of lipid within the neoplastic cells
- Microscopically, adenomas are composed of cells similar to those populating the normal adrenal cortex. The nuclei tend to be small, although some degree of pleomorphism may be encountered even in benign lesions ("endocrine atypia"). The cytoplasm ranges from eosinophilic to vacuolated, depending on their lipid content.
Adrenocortical carcinomas
These are rare and may occur at any age, including in childhood.
- Carcinomas are generally large, invasive lesions.
- The cut surface is typically variegated and poorly demarcated with areas of necrosis, hemorrhage, and cystic change.
- Microscopically, they are composed of well-differentiated cells resembling those of cortical adenomas or bizarre, pleomorphic cells, which may be difficult to distinguish from those of an undifferentiated carcinoma metastatic to the adrenal.
Peutz-Jeghers syndrome
1. Lesions appear as small, melanotic, and freckle-like. They can be found on the skin, oral mucosa, lips, feet, and hands.
2. May also present with intestinal polyps, which may develop into a gastrointestinal carcinoma.
3. Genetic transmission: autosomal dominant.
Post viral (post hepatitic) cirrhosis (15-20%)
Cause:- Viral hepatitis (mostly HBV or HCV)
Acute hepatitis → chronic hepatitis → cirrhosis.
Pathology
Liver is shrunken. Fatty change is absent (except with HCV). Cirrhosis is mixed.
M/E :-
Hepatocytes-show degeneration, necrosis as other types of cirrhosis.
Fibrous septa -They are thick and immature (more cellular and vascular).
- Irregular margins (piece meal necrosis).
- Heavy lymphocytic infiltrate.
Prognosis:- - More rapid course than alcoholic cirrhosis.Hepatocellular carcinoma is more liable to occur
Clinical genetics (cytogenetics),
This is a method in which inherited chromosomal abnormalities in the germ cells or acquired chromosomal abnormalities in somatic cells are investigated using the techniques of molecular biology.