NEET MDS Lessons
General Pathology
Pulmonary embolism
A pulmonary embolism (thromboembolism) occurs when a blood clot, generally a venous thrombus, becomes dislodged from its site of formation and embolizes to the arterial blood supply of one of the lungs.
Clinical presentation
Signs of PE are sudden-onset dyspnea (shortness of breath, 73%), tachypnea (rapid breathing, 70%), chest pain of "pleuritic" nature (worsened by breathing, 66%), cough (37%), hemoptysis (coughing up blood, 13%), and in severe cases, cyanosis, tachycardia (rapid heart rate), hypotension, shock, loss of consciousness, and death. Although most cases have no clinical evidence of deep venous thrombosis in the legs, findings that indicate this may aid in the diagnosis.
Diagnosis
The gold standard for diagnosing pulmonary embolism (PE) is pulmonary angiography
An electrocardiogram may show signs of right heart strain or acute cor pulmonale in cases of large PEs
In massive PE, dysfunction of the right side of the heart can be seen on echocardiography, an indication that the pulmonary artery is severely obstructed and the heart is unable to match the pressure.
Treatment
Acutely, supportive treatments, such as oxygen or analgesia
In most cases, anticoagulant therapy is the mainstay of treatment. Heparin or low molecular weight heparins are administered initially, while warfarin therapy is given
Malnutrition
A. Marasmus - calorie malnutrition
A child with marasmus suffers growth retardation and loss of muscle. The loss of muscle mass results from catabolism and depletion of the somatic protein compartment.
With such losses of muscle and subcutaneous fat, the extremities are emaciated; by comparison, the head appears too large for the body. Anemia and manifestations of multivitamin deficiencies are present, and there is evidence of immune deficiency, particularly of T cell-mediated immunity.
B. Kwashiorkor - protein malnutrition - importance of protein quality as well as quantity
Marked protein deprivation is associated with severe loss of the visceral protein compartment, and the resultant hypoalbuminemia gives rise to generalized, or dependent, edema.
The weight of children with severe kwashiorkor is typically 60% to 80% of normal.
However, the true loss of weight is masked by the increased fluid retention (edema).
Children with kwashiorkor have characteristic skin lesions, with alternating zones of hyperpigmentation, areas of desquamation, and hypopigmentation, giving a "flaky paint" appearance.
Hair changes include overall loss of color or alternating bands of pale and darker hair, straightening, line texture, and loss of firm attachment to the scalp.
An enlarged, fatty liver (resulting from reduced synthesis of carrier proteins) and a tendency to develop early apathy, listlessness, and loss of appetite.
The bone marrow in both kwashiorkor and marasmus may be hypoplastic, mainly because of decreased numbers of red cell precursors. How much of this derangement is due to a deficiency of protein and folates or to reduced synthesis of transferrin and ceruloplasmin is uncertain. Thus, anemia is usually present, most often hypochromic microcytic anemia, but a concurrent deficiency of folates may lead to a mixed microcytic-macrocytic anemia.
C. Most cases of severe malnutrition are a combination of A and B usually characterized by:
• Failure of growth
• Behavioral changes
• Edema (kwashiorkor)
• Dermatosis
• Changes in hair
• Loss of appetite
• Liver enlargement
• Anemia
• Osteoporosis
Acute pericarditis
1. Characterized by inflammation of the pericardium.
2. Causes include:
a. Viral infection.
b. Bacterial infection, including Staphylococcus, Pneumococcus.
c. Tuberculosis.
d. MI.
e. Systemic lupus erythematosus.
f. Rheumatic fever.
3. Signs and symptoms include:
a. Pericardial friction rub on cardiac auscultation.
b. Angina.
c. Fever.
4. Consequences include constrictive pericarditis,which results from fusion and scarring of the pericardium. This may lead to the restriction of ventricular expansion, preventing the heart chambers from filling normally.
General chromosome abnormalities
The normal human cell contains 46 chromosomes, including 22 homologous pairs of autosomes and one pair of sex chromosomes (XX for female and XY for male). A somatic cell is diploid, containing 46 chromosomes. Gametes are haploid, containing 23 chromosomes.
Aneuploidy
(a) Any deviation in the number of chromosomes, whether fewer or more, from the normal haploid number of chromosomes.
(b) Nondisjunction—a common cause of aneuploidy. It is the failure of chromosomes to pass to separate cells during meiotic or mitotic cell division.
(c) Often seen in malignant tumors.
Deletion: loss of a sequence of DNA from a chromosome.
Translocation: the separation of a chromosome and the attachment of the area of separation to another chromosome.
Multiple myeloma.
Blood picture:
- Marked rouleaux formation.
- Normpcytic normochromic anaemia.
- There may be leucopenia or leucoery!hrohlastic reaction.
- Atypical plasma cells may be seen in some patients
- Raised ESR
- Monoclonal hypergammaglobulinaemia
- If light chains are produced in excess, they are excreted in urine as bence jones protein
Bone marrow
- Hyper cellular
- Plasma cells from at least 15 – 30% atypical forms and myeloma cells are seen.
Fungal
Superficial mycoses
1. Superficial mycoses→outermost layers of the skin or its appendages; skin, nails and/or hair.
2. Dermatophytoses transmitted by contact with man (anthropophilic; weak inflammatory response), animals (zoophilic; brisk inflammatory response), or contact with soil (geophilic; strongest inflammatory response).
3. Trichophyton→hair, skin, or nails; Microsporum → hair and skin; and Epidermophyton→skin alone.
4. The diagnosis is best made by culture of skin scrapings secured from the leading edge of the lesion.
- use Wood's light to check for fluorescing metabolites.
- direct KOH preparations of the scraped material
Subcutaneous Mycoses
1. Subcutaneous mycoses are usually related to traumatic implantation into the skin.
2. Chromoblastomycosis, or verrucous (wart-like) dermatitis, is a chronic skin lesion associated with several pigmented fungi (Fonsecaea, Phialophora, and Cladosporium).
- granulomatous reaction in subcutaneous tissue are pigmented, thick walled bodies are visible in tissue section.
3. Mycetomas (maduromycosis) are characterized by a localized, tumorous nodule (usually foot) that occurs in response to chronic progressive destruction of skin, subcutaneous tissue, fascia, muscle and bone
4. Sporotrichosis is caused by the dimorphous fungus, Sporothrix schenckii.
- traumatic implantation of the fungus growing in soil, thus the association with "rose gardeners disease".
- MC lymphocutaneous disease → painless nodule at inoculation site → chain of suppurating subcutaneous nodules that drain to the skin surface along the course of the lymphatics.
- cigar shaped yeast forms are seen in the suppurative nodules and asteroid bodies (Splendore-Hoeppi phenomenon) are noted within granulomatous microabscesses.
- treatment: oral potassium iodide
Seborrheic keratosis
1. A round, brown-colored, flat wart.
2. Most often seen in middle-aged to older adults.
3. A benign lesion.