cell injury 2 (EXTRACELLULAR DEPOSITIONS) l General pathology MCQs for dental student

 

cell injury 2 (EXTRACELLULAR DEPOSITIONS) l General pathology MCQs (multiple choice question ) for dental student

 

MCQ in extracellular deposition 

AMYLOIDOSIS ( B-Fibrillosis, Amyloid Deposit)

• Definition: Amyloidosis is the extracellular deposition of amyloid.an abnormal protein. Amyloid is deposited in the walls of small blood vessels.

• on reticulin fibers and basement membranes. In sections stained by hematoxylin and eosin amyloid deposit appears as homogenous refractile pale pink material.

Staining of Amyloid Deposit:

• Gross staining(staining of a slice of tissue):
• Dark brown with Lugol's iodine, the rest of the tissue stains pale yellow.
• Blue with iodine and 1% sulphuric acid.

Microscopic staining:

• Pink (pale red)with eosin stain.
• Orange red with Congo red stain. When the same sections are examined under polarizing light, amyloid gives apple-green bipolar refringence
• Rose red with metachromatic stains e.g. methyl violet, gentian violet and crystal violet. The rest of the tissues stain violet.

Nature of Amyloid Deposit:

• 90% of the amyloid deposit consists of fibril proteins, the remaining
• 10% is a glycoprotein called P component. Amyloid fibril proteins are of two types:

Amyloid light chain (AL) protein:

1. Light chains of immunoglobulins
2. formed by plasma cells.

Amyloid-associated(AA)protein:

• Non immunoglobulins derived from a precursor in the serum called serum amyloid associated (SAA) protein.

• SAA protein is synthesized by the liver. The level of SAA protein is markedly increased in chronic inflammatory and destructive diseases.

Types of Amyloidosis:

1. Localized amyloidosis.
2. Systemic(generalized)amyloidosis:

• Primary amyloidosis.
• Secondary amyloidosis.
• Hemodialysis associated amyloidosis.
• Hereditary amyloidosis.

LOCALIZED AMYLOIDOSIS

• Amyloid deposit restricted to one organ or tissue. The cause is unknown. The deposited fibril protein varies in different cases. The deposit occurs mainly in:

1. Laryngeal wall forming small tumor-like nodules.
2. Skin, bronchi, lung, heart and urinary bladder.
3. Tumors of endocrine glands as medullary carcinoma of thyroid, beta cell adenoma of pancreas and pheochromocytoma of adrenal medulla.
4. The amyloid deposit within medullary carcinoma of thyroid is procalcitonin produced by the tumor cells.
5. Cerebral grey matter in senile dementia. The amyloid deposit is B2 amyloid protein (AB2).

SYSTEMIC AMYLOIDOSIS

• Renal failure is the cause of death.

Primary Amyloidosis

• Rare and occurs in old people, in some cases without predisposing disease. in others as a complication of multiple myeloma and other B-cell neoplasms. The deposited fibril is AL protein.

• Amyloid deposition is often severe in the heart, tongue, alimentary tract, skeletal muscles and the solid abdominal organs specially the kidney. Death results from cardiac or renal failure.

Secondary Amyloidosis

• The deposited fibril protein is AA protein. This type is common and complicates the following diseases:

1. Rheumatoid arthritis.
2. Chronic suppurations: e.g. chronic suppurative osteomyelitis, chronic suppurative arthritis, chronic suppurative pyelonephritis, chronic lung abscess, bronchiectasis and chronic empyema.
3. Infective granulomas: e.g. chronic tuberculosis of the lung, bone and joints, tertiary syphilis, leprosy and actinomycosis.
4. Malignant tumors: e.g. gastric carcinoma, renal cell carcinoma and Hodgkin's disease.
5. The organs commonly affected are the kidney, liver, spleen and adrenal.

Hemodialysis Associated Amyloidosis

• Amyloidosis affects up to 70%of patients with chronic renal failure subjected to chronic hemodialysis.

• The deposit is amyloid protein B2- microglobulin which is not filtered by normal dialysis membranes. The deposits affect joints and periarticular tissues.

Hereditary Amyloidosis

• As in familial Mediterranean fever and hereditary neuropathy. The amyloid is AA protein or prealbumin (Transthyretin).

Pathological Picture of Affected Organs:

• The organ affected by amyloidosis is : liver , kidney , renal and spleen

Liver:

• Gross picture: The liver is enlarged, heavy, firm and rubbery. The borders are sharp. The cut surface shows waxy light brown streaks of amyloid deposit on a yellowish brown back ground of hepatic tissue (fatty degeneration).

Microscopic picture: Homogenous pink amyloid deposits in:

• Walls of hepatic arterioles and venules causing thickening of the wall and narrowing of the lumen.

• Walls of the sinusoids , between the endothelium and the liver cells starting in the intermediate zone of the lobules and spreading in both directions. The liver cells degenerate and undergo atrophy from anoxia and pressure of the amyloid material. The sinusoids become narrowed.

Kidney:

• Gross picture: The kidney is enlarged. The cut surface is waxy, pale yellow due to fatty degeneration and shows light brown dots caused by amyloid deposit in the glomeruli. In long standing cases secondary ischemic changes result in a small contracted kidney.

Microscopic picture: Homogenous pink amyloid is deposited in:

• Walls of the arterioles and venules causing their thickening and narrowing. The resulting ischemia causes fatty degeneration in the convoluted tubules followed by tubular atrophy and fibrosis. A secondary contracted kidney results and ends by renal failure.

• Basement membrane of the glomerular capillaries leading to protein loss in urine. Hypoproteinemia and generalized edema occurs. The condition is called nephrotic syndrome.

• Basement membrane of the collecting tubules preventing water reabsorption and causing diabetes insipidus.

Spleen: Two types occur, intermediate pictures are present.

Sago spleen (focal type) :

• The amyloid material is deposited in the wall of the central arterioles of the lymph follicles. The lumen of the arterioles becomes narrowed.

• The follicles undergo pressure atrophy and are gradually replaced by the amyloid deposit. The organ is moderately enlarged, rubbery and firm.

• The cut surface shows many glossy light brown bodies which represent follicles with amyloid deposit against a red background.

Diffuse amyloid spleen:

• A less common type. There is a wide spread deposit of amyloid in the reticulum of red pulp and walls of the sinusoids. The lymph follicles are compressed, atrophic and widely separated. 

• The spleen is markedly enlarged. The cut surface shows light brown streaks of amyloid deposit or a homogenous affection.

Gastro-intestinal Tract:

• Amyloid deposit in the gastrointestinal tract is common and affects any part. Amyloid deposit in the tongue causes macroglossia. Amyloid deposit in the intestine causes mucosal atrophy.

• The effects of gastrointestinal amyloidosis include obstruction , malabsorption, protein loss, hemorrhage and diarrhea.

Heart:

• The heart is enlarged and the myocardium is thickened and firm. Amyloid is deposited in the interstitial tissue surrounding and replacing muscle fibers as well as in the walls of small blood vessels.

• The effects are cardiac arrhythmias and heart failure.

Adrenal Glands:

• The glands are enlarged due to amyloid deposit in the cortex. Bilateral adrenal cortical destruction causes Addison's disease.

Diagnosis of Amyloidosis in Life:

• Biopsy: From the gingiva or rectal mucosa.
• Congo red test: 10-30 % of the dye injected intravenously disappears from the blood of normal persons in one hour. Disappearance of 60 % or more indicates amyloidosis as the amyloid absorbs the dye.The method is not in common use because fatal anaphylactic reaction may occur.

MYXOMATOUS CHANGE (Myxomatous Degeneration)

• Pathological accumulation of mucoid material in the connective tissue giving it a picture similar to the myxomatous tissue of the umbilical cord.

• The affected tissue becomes soft, transparent and jelly-like.

• Microscopically the cells are round, oval, spindle and stellate with interlacing thin branches and a homogenous pale blue mucoid matrix in between.

• It occurs in mesodermal tumors as leiomyoma, neurofibroma and chondroma and in the subcutaneous connective tissue in myxoedema.

GOUT

• Disturbance in purine metabolism with sodium urates deposition in the tissue.

Causes:

• Primary type: Hereditary and occurs mainly in middle aged males.
• Secondary type: Caused by increased nucleoprotein breakdown as in chronic leukaemias.

Pathological Features:

• Increased level of blood uric acid to 6-12 mgm.per 100 ml.(normal level is 3-6 mgm.per 100 ml.).
• Monosodium urate crystals deposit in ; The deposit forms small masses called tophi :

1. Joint structures as the articular cartilage, synovial membrane, capsule, ligaments and tendons. The lesion mainly affects the metatarso-phalangeal joint of big toe.
2. Cartilage of the nose, ear and eyelids.
3. Interstitial tissue of the kidney.
4. Cardiac valves.

• The affected cartilage is thin, eroded and shows white plaques of urate deposits. The covering skin may ulcerate.
• Microscopically the tissue shows needle shaped mono-sodium urate crystals surrounded by a foreign body granuloma.
• Renal failure in chronic cases.

PATHOLOGICAL CALCIFICATION

• Pathological deposition of calcium salts (phosphate and carbonate) in sites other than bone and teeth.

Dystrophic Calcification:

• Pathological deposition of calcium salts in injured and necrotic tissues. It is the commonest type of pathological calcification.

Cause:

• This type occurs with normal blood calcium. The cause may be a local alkalinity in the necrotic tissue, increased phosphatase activity or release of phosphate from nucleoprotein breakdown.

Gross picture:

• The calcified tissue appears opaque white and hard in consistency. The cut surface is finely granular.

Microscopic picture:

• Calcium stains dark blue with haematoxylin.

Examples:

• In injured (degenerated) tissues as:

1. Atheroma.
2. Chronic rheumatic valvulitis.
3. Degenerated tumors (as myoma).
4. Old scars.

• In necrotic tissues as:

1. Old thrombi.
2. Old infarcts.
3. Fat necrosis.
4. Caseous tuberculous lesions.
5. Dead parasites as bilharzia ova and worms.
6. Lithopedion(a calcified retained fetus).

Metastatic Calcification

• Pathological deposition of calcium salts in living tissue.

Cause: Elevation of the blood calcium level due to:

• Increased calcium absorption from the intestine as in hyper vitaminosis D and excess milk intake for treatment of peptic ulcer.

• Increased calcium mobilization from the bones as in hyperparathyroidism, prolonged immobilization and bone destruction by malignant tumors as multiple myeloma and metastatic carcinoma.

Sites:

• Renal tubules(nephrocalcinosis).
• Mucosa of the stomach.
• Walls of the lung alveoli.
• Media of the blood vessels.
• In the first three sites relative alkalinity of the tissues predisposes to calcium deposition(these tissues secrete or excrete acid substances). Also with elevated blood calcium deposition occurs in any focus of dead tissue.

Calcinosis:

• A rare type of pathological calcification of unknown cause. Calcification is either:

1. Circumscribed(localized):In the skin and subcutaneous tissue.
2. Generalized (calcinosis universalis) : In the skin, subcutaneous tissue. fasciae, tendons, muscles and nerves.

Stone Formation:

• Calcium salts deposition in the cavities of hollow organs as urinary and biliary tract stones.