NEET MDS Lessons
General Pathology
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
Fanconi’s syndrome
Characterized by the failure of the proximal renal tubules to resorb amino acids, glucose, and phosphates.
May be inherited or acquired.
Clinical manifestations include
glycosuria, hyperphosphaturia, hypophosphatemia, aminoaciduria, and systemic acidosis.
Ichthyosis vulgaris is a genetic disease characterized by increased cohesiveness of the cells in the stratum corneum, resulting up in a piling up stratum corneum (scales like a fish).
Acute viral hepatitis
Clinical features. Acute viral hepatitis may be icteric or anicteric. Symptoms include malaise, anorexia, fever, nausea, upper abdominal pain, and hepatomegaly, followed by jaundice, putty-colored stools, and dark urine.
In HBV, patients may have urticaria, arthralgias, arthritis, vasculitis, and glomerulonephritis (because of circulating immune complexes). Blood tests show elevated serum bilirubin (if icteric), elevated transaminases, and alkaline phosphatase.
The acute illness usually lasts 4-6 weeks.
Pathology
(1) Grossly, there is an enlarged liver with a tense capsule.
(2) Microscopically, there is ballooning degeneration of hepatocytes and liver cell necrosis.
Lymphomas
A. Hodgkin’s disease
1. Characterized by enlarged lymph nodes and the presence of Reed-Sternberg cells (multinucleated giant cells) in lymphoid tissues.
2. Disease spreads from lymph node to lymph node in a contiguous manner.
3. Enlarged cervical lymph nodes are most commonly the first lymphadenopathy observed.
4. The cause is unknown.
5. Occurs before age 30.
6. Prognosis of disease depends largely on the extent of lymph node spread and systemic involvement.
B. Non-Hodgkin’s lymphoma
1. Characterized by tumor formation in the lymph nodes.
2. Tumors do not spread in a contiguous manner.
3. Most often caused by the proliferation of abnormal B cells.
4. Occurs after age 40.
5. Example: Burkitt’s lymphoma
a. Commonly associated with an EpsteinBarr virus (EBV) infection and a genetic mutation resulting from the translocation of the C-myc gene from chromosome 8 to 14.
b. The African type occurs in African children and commonly affects the mandible or maxilla.
c. In the United States, it most commonly affects the abdomen.
d. Histologically, the tumor displays a characteristic “starry-sky” appearance.
German measles (rubella)
- sometimes called "three day measles".
- incubation 14-21 days; infectious 7 days before the rash and 14 days after the onset of the rash.
- in adults, rubella present with fever, headache, and painful postauricular Lymphadenopathy 1 to 2 days prior to the onset of rash, while in children, the rash is usually the first sign.
- rash (vasculitis) consists of tiny red to pink macules (not raised) that begins on the head and spreads downwards and disappears over the ensuing 1-3 days; rash tends to become confluent.
- 1/3rd of young women develop arthritis due to immune-complexes.
- splenomegaly (50%)
SHOCK
Definition. It is a clinical state of acute inadequacy of perfusion to tissues due to fall in effective circulating blood volume.
This inadequacy can be caused by :
- Increased vascular capacity
- Decreased blood volume
- Altered distribution of available blood
- Defective pumping system
Causes:
(1) Hypovolemic
- Massive hamorrhage (external or internal).
- Loss of plasma as in bums.
- Dehydration due to severe vomiting, diarrhea diabetic coma.
- Generalized capillary permeability as in anaphylaxis.
(2) Cardiogenic
- Myocardial infarction.
- Pulmonary embolism.
- Cardiac tamponade
(3) Peripheral pooling:
- Endotoxic shock.
- Disseminated intravascular coagulation (DIC).
(4) Neurogenic:
- Syncope.
- Contributory factor in trauma, bums etc.
Metabolic changes in shock
- Hyperglycaemia due to glycogenolysis.
- Increased blood lactate and pyruvate due to anaerobic glycolysis. This results in metabolic acidosis.
- Protein catabolism and increased blood urea.
- Interference with enzyme systems.
Organs involved in shock
(1) Kidneys:
- Renal tubular necrosis.
- Cortical necrosis.
(2) Lungs:
- Oedema, congestion and haemorrhage.
- Microthrombi.
(3) G.I.T. :
- Mucosal oedema.
- Ulceration and haemorrhage
(4) Degeneration and focal necrosis in:
- Heart.
- Liver.
- Adrenals
(5) Anoxic encephalopathy