calcification, pigments & amyloid Flashcards
what is calcification
- abnormal deposition of calcium salts (along with iron, magnesium, and other minerals) in tissues
- seen as dark blue granular material on H&E stained sections
what is dystrophic calcification (mineralization)
- calcification of necrotic tissue in an animal with normal serum calcium
- Ca accumulates in the mitochondria, since dead cells cannot regulate influx of calcium into cytosol
- ex: necrotic skeletal muscle, granulomas, dead parasites, necrotic abdominal tissue secondary to pancreatitis
what is metastatic calcification (mineralization)
- occurs in living tissues as a result of hypercalcemia
- begins in the interstitium (extracellular space) of organs affected (kidney, lung, blood vessels, stomach)
what are causes of hypercalcemia
- hypercalcemia of malignancy (lymphomas, anal sac gland carcinomas, parathyroid-like hormone - PTH-rP- produced by these tumors)
- primary hyperparathyroidism (due to parathyroid adenomas) (VD toxicity - plant-derived, therapeutic overdoses, cholecalciferol rodenticides)
- destruction of bone from primary or metastic neoplasia (rare)
metastatic mineralization
what is uremic mineralization
- renal failure
- abnormal Ca:Phos ratio
- hypo-, normo- or hypercalcemic
- tongue, parietal pleura, pulmonary interstitium, left atrium, kidney, gastric mucosa
what are pigments
colored substances that can be either exogenous or endogenous
what are the 4 major endogenous pigments
- hemosiderin
- bilirubin
- melanin
- lipofuscin/ceroid
what is hemosiderin
- hemoglobin-derived globular golden-yellow to yellow-brown pigment
- found in macrophages at sites of erythrocyte lysis or breakdown
- small amounts normally present in bone marrow, spleen and liver
- following lysis of RBC, iron is sequestered by macrophages and eventually converted to hemosiderin in lysosomes
- hemosiderin is positive with prussian blye staining
what is bilirubin
- jaundice (icterus) is the clinical manifestation of hyperbilirubinemia and is the yellowish staining of the integument, sclera, and deeper tissues with bile pigments resulting from increased levels of bilirubin in plasma
- green-brown, amorphous, globular pigment
- major component of bile, waste product
- does NOT contain iron
- RBC breakdown -> heme portion of hemoglobin converted to biliverdin and then bilirubin by chemical rx
- bound to albumin in blood
what is pre-hepatic icterus
hemolytic
- due to massive breakdown of erythrocytes; many different causes (immune medated, infectious, metabolic, trauma)
- causes increased unconjugated bilirubin; quickly converted into conjugated
what is hepatic icterus
- hapatocellular disease comprises the liver’s ability to uptake unconjugated bilirubin and/or excrete conjugated bilirubin into bile canaliculus
- increase in both unconjugated and conjugated bilirubin
what is post-hepatic icterus
- bile duct obstruction
- increase in conjugated bilirubin
endogenous hemoglobin derived pigments after a contusion (bruise):
- blunt trauma
- damage to local blood vessels
- extravasation of blood (hemorrhage)
- lysis of erythrocytes
- RBC debris is phagocytized by macrophages
- hemoglobin is degraded by lysosomes
- red-blue (hemoglobin)
- green-blue (biliverdin and bilirubin) and hemosiderin (golden yellow)
what is vitiligo
partial or patchy loss of melanin pigment - depigmentation
what is albinism
mutation in the tyrosinase gene - too little melanin
what is hyperpigmentation
develop secondary to almost any cutaneous insult (damage to melanocytes can also result in this)
melanin
what is neoplasia
benign melanocytoma or malignant melanoma
what is lipofuscin
- brownish-yellow intracellular pigment
- increases w/ age and atrophy
- “wear and tear” or “aging” pigment
- liver, heart, brain, thyroid gland, adrenal glands, macrophages
- formed in lysosomes
- derived from free radical oxidation of unsaturated lipids, has proteins
- not harmful to cell but marker of past free radical injury
what is ceroid
common histologic and histochemical features with lipofuscin; produced by macrophages and accumulates in disease states (VE dificiency)
what is amyloid
- diverse group of proteinaceous substances with a similar appearance, depsited in organs
- causes atrophy or impaired function
what are characteristics common to all types of amyloid
- smooth fibrillar and eosinophilic using hematoxyin and eosin (H&E) stains
- stains red with congo red stain and has apple-green birefringence when viewed with polarized light
- molecular structure is a beta-pleated sheet
what is light chain (AL) amyloid (primary)
- made up of monoclonal immunoglobulin light chains
- seen with plasma cell dyscrasias and plasma cell tumors and equine nodular cutaneous amyloidosis
- NOT related to inflammation
what is reactive (AA) amyloid (secondary)
- made up of serum amyloid-associated (SAA) protein (an acute phase protein produced by the liver during inflammation)
- seen after chronic antigenic stimulation and chronic inflammation
- familial in Shar Pei dogs and Abyssinian and some Siamese cats
what is islet amyloid (IAPP)
- precursor polypeptide is co-secreted with insulin by the beta cells in the pancreatic islets; deposition in pancreatic islets in aged cats; has been associated with diabetes mellitus; many old cats have islet amyloidois and do NOT have diabetes mellitus
