Difference between revisions of "Pigmentation - Pathology"
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+ | |||
==Exogenous Pigmentation== | ==Exogenous Pigmentation== | ||
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* Black or grey speckles in lungs. | * Black or grey speckles in lungs. | ||
− | ====Histological | + | ====Histological Apprearance==== |
* Black extra- or intra-cellular granules . | * Black extra- or intra-cellular granules . | ||
Line 49: | Line 50: | ||
*** Yolks of eggs. | *** Yolks of eggs. | ||
*** Fat of horses and Channel Island cattle. | *** Fat of horses and Channel Island cattle. | ||
− | * May be confused with a [[ | + | * May be confused with a [[Pigmentation and Calcification - Pathology#Jaundice|jaundiced]] liver or subcutis. |
** Adding minced tissue to a mixture of ether and water can distinguish the two. | ** Adding minced tissue to a mixture of ether and water can distinguish the two. | ||
*** Carotenoids are fat-soluble and dissolve in the ether fraction. | *** Carotenoids are fat-soluble and dissolve in the ether fraction. | ||
Line 93: | Line 94: | ||
** For example, in wound healing. | ** For example, in wound healing. | ||
*** [[Healing and Repair - Pathology#Scarring|Scars]] are pigmented. | *** [[Healing and Repair - Pathology#Scarring|Scars]] are pigmented. | ||
− | * Hyperpigmentation may be significant in excess cortisol states such as [[ | + | * Hyperpigmentation may be significant in excess cortisol states such as [[Adrenal Glands - Pathology#Adrenal Hyperfunction|Cushing’s Disease]]. |
** There may be tumours of melanocytes. | ** There may be tumours of melanocytes. | ||
* Albinos have no pigment in their hair or skin, and have pink irises. | * Albinos have no pigment in their hair or skin, and have pink irises. | ||
Line 190: | Line 191: | ||
**** This parasitic haematin is in an un-resorbable form, and so the flukes lead to hypoproteinaemia and anaemia. | **** This parasitic haematin is in an un-resorbable form, and so the flukes lead to hypoproteinaemia and anaemia. | ||
− | ====[[Icterus| | + | ====Jaundice==== |
+ | |||
+ | * Jaundice is also known as icterus. | ||
+ | * Jaundice is a yellowish discoloration due to excessive levels of bilirubin in plasma. | ||
+ | ** Seen in tissues that are normally white, e.g. | ||
+ | *** Fat | ||
+ | *** Intima of blood vessels | ||
+ | *** Sclera | ||
+ | * Bilirubin stains brown with H&E, like both haemosiderin and lipofuscin. | ||
+ | ** Must be distinguished from each other by special stains. | ||
+ | *** Bilirubin stains bright green with a Fouchet stain. | ||
+ | |||
+ | =====Production of Bilirubin===== | ||
+ | |||
+ | * Red blood cells either undergo: | ||
+ | ** Phagocytosis, in the case of ageing cells. | ||
+ | ** Haemolysis, in haemolytic crises. | ||
+ | * Haemoglobin is freed from the red cells and is further broken down in the reticulo-endothelial system to haeme and globulin. | ||
+ | ** Haeme is a mixture of iron and porphyrin. | ||
+ | ** Both the iron and globulin are recycled for further use in erythropoiesis. | ||
+ | * The porphyrin from haemoglobin breakdown is converted to biliverdin. | ||
+ | ** A green pigment | ||
+ | *** May contribute to the greenish appearance seen in local bruising. | ||
+ | * Biliverdin is subsequently changed into bilirubin. | ||
+ | * The bilirubin is then bound to albumin, and transported in the blood to the [[Liver - Anatomy & Physiology|liver]]. | ||
+ | ** In the hepatocyte, bilirubin is released from the albumin and conjugated with glucuronic acid. | ||
+ | *** Forms conjugated bilirubin. | ||
+ | **** Excreted into the intestine via the bile ducts. | ||
+ | |||
+ | ===== Prehepatic (Haemolytic) Icterus===== | ||
+ | |||
+ | * Due to excessive production of bilirubin due to haemolysis, e.g. | ||
+ | ** [[Babesia|Babesiosis]] | ||
+ | ** [[Leptospira|Leptospirosis]] | ||
+ | ** Copper poisoning in sheep. | ||
+ | * There is excessive unconjugated bilirubin in the blood. | ||
+ | |||
+ | =====Hepatic (Toxic) Icterus===== | ||
+ | |||
+ | * Due to [[Liver - Anatomy & Physiology|liver]] cell damage. | ||
+ | ** In hepatocytic [[Necrosis - Pathology|necrosis]], the liver cannot conjugate bilirubin. | ||
+ | *** Results in increased levels of unconjugated bilirubin in the blood. | ||
+ | ** In less severe damage, the hepatocytes swell and bile caniculi are pressed closed. | ||
+ | *** There is therefore intrahepatic obstruction conjugated bilirubin accumulated in the blood. | ||
+ | * In reality, these situations occur together. | ||
+ | ** There is both excessive unconjugated and conjugated bilirubin in the blood. | ||
+ | * Examples: | ||
+ | ** [[Leptospira|''Leptospira icterohaemorrhagica'']] in the dog. | ||
+ | ** Rift Valley fever virus. | ||
+ | ** Some plant poisonings. | ||
+ | *** Lantana. | ||
+ | ** Some fungal infections. | ||
+ | *** Aflatoxicosis. | ||
+ | |||
+ | =====Post-Hepatic (Obstructive) Icterus===== | ||
+ | |||
+ | * Due to the flow of bile being obstructed, for example by: | ||
+ | ** [[Biliary Tract - Obstruction|Gallstones]] | ||
+ | ** [[Parasites|Parasites]] | ||
+ | *** [[Ascaris suum|''Ascaris suum'']] in the bile ducts of pigs. | ||
+ | ** [[Neoplasia - Pathology|Tumours]] | ||
+ | *** Adenocarcinoma of pancreas presses upon and occludes the bile duct. | ||
+ | * Results in excessive conjugated bilirubin in the blood. | ||
+ | * Constructive icterus causes, out of the three types of icterus, | ||
+ | ** The most elevated levels of bilirubin in the blood | ||
+ | ** The greatest discoloration of the tissues of the body. | ||
+ | |||
+ | =====Van de Berg Test===== | ||
+ | |||
+ | * This test can distinguish between the different types of jaundice, based on whether the bilirubin is conjugated or not. | ||
+ | * Plasma from the jaundiced animal is treated with an aqueous solution of a reagent (diazotised sulphanilic acid). | ||
+ | ** Gives a red-purple colour. | ||
+ | *** The intensity of this colour is directly proportional to the amount of water-soluble (i.e. conjugated ) bilirubin in the sample. | ||
+ | ** Further addition of alcohol intensifies the colour if there is non-water-soluble (i.e. unconjugated) bilirubin also present. | ||
+ | *** The intensified colour is directly proportional to the total amount of bilirubin present in the sample. | ||
+ | ** The difference between the two readings gives the amount of unconjugated bilirubin in the sample. | ||
====Haematoidin==== | ====Haematoidin==== | ||
Line 220: | Line 296: | ||
* Found in [[Macrophages|macrophages]] of [[Bone Marrow - Anatomy & Physiology|bone marrow]], [[Liver - Anatomy & Physiology|liver]], lungs, and [[Lymph Nodes - Anatomy & Physiology|lymph nodes]]. | * Found in [[Macrophages|macrophages]] of [[Bone Marrow - Anatomy & Physiology|bone marrow]], [[Liver - Anatomy & Physiology|liver]], lungs, and [[Lymph Nodes - Anatomy & Physiology|lymph nodes]]. | ||
− | ===== | + | =====Photosensitisation===== |
* Porphyrin is a fluorescent pigment. | * Porphyrin is a fluorescent pigment. | ||
Line 254: | Line 330: | ||
* Lipofuscin is the ageing pigment. | * Lipofuscin is the ageing pigment. | ||
** Can be seen in senile animals in | ** Can be seen in senile animals in | ||
− | *** [[ | + | *** [[Muscles Degenerative - Pathology#Pigmentation|Muscle]] |
− | **** E.g. in "[[Cell Growth | + | **** E.g. in "[[Disorders of Cell Growth - Pathology#Brown Atrophy|brown atrophy]]". |
*** Myocardium | *** Myocardium | ||
*** Neurones (particularly those of horses) | *** Neurones (particularly those of horses) | ||
Line 290: | Line 366: | ||
** A variety of tissues including fat, cardiac muscle, splenic trabeculae and intestine in Vitamin E deficiency. | ** A variety of tissues including fat, cardiac muscle, splenic trabeculae and intestine in Vitamin E deficiency. | ||
*** Sometimes being so prominent as to be grossly visible. | *** Sometimes being so prominent as to be grossly visible. | ||
− | **** | + | **** Yellow fat disease |
***** Pigs and cats | ***** Pigs and cats | ||
**** Brown gut | **** Brown gut | ||
***** Dogs | ***** Dogs | ||
− | |||
− | |||
− | |||
[[Category:General Pathology]] | [[Category:General Pathology]] |
Revision as of 12:17, 15 February 2011
Exogenous Pigmentation
- Enter body from environment
Carbon (Anthracosis)
- This occurs where carbon particles are inhaled over a long period of time.
- Carbon particles are phagocytosed by alveolar Macrophages.
- Are carried to a peribronchiolar location and the local bronchial lymph nodes.
- It is common in animals that live in cities.
- There is air pollution due to smoke.
- Mostly seen in dogs.
- Can occur in the mesenteric lymph nodes of pigs that feed on ash heaps.
- Carbon is insoluble and results in minimal irritation.
Gross Appearance
- Black or grey speckles in lungs.
Histological Apprearance
- Black extra- or intra-cellular granules .
- Resistant to solvents and bleaching agents.
- Can cause slight fibrosis in alveolar walls.
Pneumoconiosis
- A serious pigmentation.
- Results from repeated inhalation of irritating mineral dust, e.g.
- Coal
- Silica
- Asbestos
- Leads to pulmonary fibrosis.
- Varying shades of grey.
- Asbestos may also cause pulmonary, pleural and peritoneal tumours.
- Seen more in man than animals.
- Occupational hazards.
Carotenoids
- Also known as lipochrome.
- Carotenoids are fat-soluble greenish-yellow pigments that bind to lipids in body.
- Derived from carotenes and xanthophyll in plants.
- Can be seen grossly in a number of normal places
- Adrenal cortex.
- Testes.
- Corpus luteum.
- Liver.
- Yolks of eggs.
- Fat of horses and Channel Island cattle.
- May be confused with a jaundiced liver or subcutis.
- Adding minced tissue to a mixture of ether and water can distinguish the two.
- Carotenoids are fat-soluble and dissolve in the ether fraction.
- Bile pigments dissolve in the water fraction.
- Adding minced tissue to a mixture of ether and water can distinguish the two.
Iatrogenic
- E.g.
- Iron injections in piglets.
- Coloured antiseptics.
- Tattooing.
Endogenous Pigmentation
- Pigments are formed inside the body.
Melanin
- Normally gives visible colour to the skin, hair, and iris.
- Melanin synthesis is controlled by melanocyte stimulating hormone (MSH).
- MSH is produced in the pituitary.
- Melanin is derived from tyrosine (an amino acid) utilising a copper-containing enzyme, tyrosinase.
- Melanosis occurs when excessive quantities of pigment are deposited in internal organs.
- The lungs and aorta, pleura, brain and meninges, and liver are often affected.
Gross Appearance
- Black/brown pigmentation is seen, either as spots or as larger areas.
- Larger areas can give the lungs or liver a chequer-board pattern.
- No change in structure occurs.
Histological Appearance
- Round granules of brown/black are seen in the cytoplasm of cells.
- Can be bleached out by chlorine or KMNO4.
- Stain black with silver stain Masson Fontana.
Significance
- There is no significance of melanosis when it occurs in the internal organs.
- There is also no significance in hyperpigmentation of the skin.
- Melanosis may be associated with chronic irritation.
- For example, in wound healing.
- Scars are pigmented.
- For example, in wound healing.
- Hyperpigmentation may be significant in excess cortisol states such as Cushing’s Disease.
- There may be tumours of melanocytes.
- Albinos have no pigment in their hair or skin, and have pink irises.
- Lack sufficient tyrosinase enzyme in their melanocytes.
- Albino rabbits, rats and mice are seen.
Blood Pigments
- Blood pigments causing pigmentation may be
- Normal derivatives of haemoglobin, which have accumulated in excess.
- Haemosiderin.
- Bilirubin.
- Pathological
- Methaemoglobin (chocolate brown) in nitrate poisoning.
- Carboxyhaemoglobin (bright cherry red) in carbon monoxide poisoning.
- Parasitic acid haematin.
- Normal derivatives of haemoglobin, which have accumulated in excess.
Haemoglobin
- Results from excessive phagocytosis or haemolysis of red blood cells.
- Haemoglobin is freed into the plasma which becomes red.
- If there is sufficient haemolysis, the haemoglobin overspills into the urine.
- Haemoglobinuria.
- Both the kidneys and the urine appear dark red.
- Haemoglobinuria.
- Can be caused by a variety of agents including:
- Bacteria
- E.g. Leptospira
- Protozoa
- E.g. Babesia bigemina
- Chemicals
- E.g. excessive copper in the liver of sheep.
- Immune mediated conditions
- E.g. autoimmune mediated haemolytic anaemia.
- Bacteria
- Haemoglobin is not usually seen in the tissues.
Haemosiderin
- Haemosiderin is a golden brown/yellow pigment.
- Derived from splitting haemoglobin into an iron-porphyrin compound and globulin.
- This splitting occurs when ageing red blood cells are engulfed by macrophages in the spleen, lymph nodes, bone marrow and liver.
- The iron containing fragment remains in the macrophages and is recycled to make more haemoglobin.
- This splitting occurs when ageing red blood cells are engulfed by macrophages in the spleen, lymph nodes, bone marrow and liver.
- Derived from splitting haemoglobin into an iron-porphyrin compound and globulin.
- Excessive quantities of haemosiderin arise from increased red cell breakdown by:
- Phagocytosis
- Haemolysis
- Large amounts of haemosiderin diffusely spread throughout the spleen usually indicates a haemolytic disorder.
- Local production of haemosiderin is responsible for the appearance of bruising in injury.
- Other haemoglobin breakdown products are also formed.
- Haemosiderin also accumulates in chronic congestion of the vascular system due to heart failure.
Gross Appearance
- Grossly, very little can be seen unless there has been substantial breakdown of haemoglobin.
- In this case the organ may appear brownish.
- Also seen as bruising.
- Usually not appreciable in the lung in heart failure.
- In repetitive exercise induced pulmonary haemorrhage of horses, the affected area of the dorsal lung may be brownish in colour.
- The equine liver often contains stores of haemosiderin giving them a brownish colour.
Histological Appearance
- Accumulates in the cytoplasm of macrophages.
- Chronic congestion in the lung can be seen due to heart failure.
- Some of the red blood cells escape out of the alveolar capillaries and are engulfed by alveolar macrophages.
- Called "heart failure" cells.
- Some of the red blood cells escape out of the alveolar capillaries and are engulfed by alveolar macrophages.
- Prussian blue stains specifically for haemosiderin.
- Granules stain blue.
Haematin
- There are 2 types of haematin.
- Acid haematin
- Parasitic haematin.
Acid Haematin
- A pigment artefact.
- Acid in unbuffered formalin binds with haemoglobin to form a brownish-black granular pigment.
- Only seen microscopically.
- Can be formed in areas of ante-mortem ulceration of the stomach.
- There is increased acidity due to hydrochloric acid.
- Acid haematin is iron negative.
- Must remove acid haematin prior to staining sections to allow haemosiderin to be distinguished.
- A useful clue in the untreated section is the presence of the pigment in the red blood cells of vessels.
Parasitic Haematin
- Certain parasites in other parts of the world (e.g. Schistosoma sp.) take up blood.
- Break haemoglobin to haematin.
- Regurgitate the pigment back into circulation.
- Taken up by macrophages, which go the lymph nodes, liver and spleen.
- Fasciola hepatica in this country causes chronic damage to the bile ducts of the bovine liver.
- Produces acid haematin, which lines the bile ducts.
- The fluke and its spines damage the duct lining and feed on blood liberated from the blood vessels.
- This is regurgitated by the fluke and passes down the bile duct to the intestine together with the proteins liberated.
- This parasitic haematin is in an un-resorbable form, and so the flukes lead to hypoproteinaemia and anaemia.
- This is regurgitated by the fluke and passes down the bile duct to the intestine together with the proteins liberated.
Jaundice
- Jaundice is also known as icterus.
- Jaundice is a yellowish discoloration due to excessive levels of bilirubin in plasma.
- Seen in tissues that are normally white, e.g.
- Fat
- Intima of blood vessels
- Sclera
- Seen in tissues that are normally white, e.g.
- Bilirubin stains brown with H&E, like both haemosiderin and lipofuscin.
- Must be distinguished from each other by special stains.
- Bilirubin stains bright green with a Fouchet stain.
- Must be distinguished from each other by special stains.
Production of Bilirubin
- Red blood cells either undergo:
- Phagocytosis, in the case of ageing cells.
- Haemolysis, in haemolytic crises.
- Haemoglobin is freed from the red cells and is further broken down in the reticulo-endothelial system to haeme and globulin.
- Haeme is a mixture of iron and porphyrin.
- Both the iron and globulin are recycled for further use in erythropoiesis.
- The porphyrin from haemoglobin breakdown is converted to biliverdin.
- A green pigment
- May contribute to the greenish appearance seen in local bruising.
- A green pigment
- Biliverdin is subsequently changed into bilirubin.
- The bilirubin is then bound to albumin, and transported in the blood to the liver.
- In the hepatocyte, bilirubin is released from the albumin and conjugated with glucuronic acid.
- Forms conjugated bilirubin.
- Excreted into the intestine via the bile ducts.
- Forms conjugated bilirubin.
- In the hepatocyte, bilirubin is released from the albumin and conjugated with glucuronic acid.
Prehepatic (Haemolytic) Icterus
- Due to excessive production of bilirubin due to haemolysis, e.g.
- Babesiosis
- Leptospirosis
- Copper poisoning in sheep.
- There is excessive unconjugated bilirubin in the blood.
Hepatic (Toxic) Icterus
- Due to liver cell damage.
- In hepatocytic necrosis, the liver cannot conjugate bilirubin.
- Results in increased levels of unconjugated bilirubin in the blood.
- In less severe damage, the hepatocytes swell and bile caniculi are pressed closed.
- There is therefore intrahepatic obstruction conjugated bilirubin accumulated in the blood.
- In hepatocytic necrosis, the liver cannot conjugate bilirubin.
- In reality, these situations occur together.
- There is both excessive unconjugated and conjugated bilirubin in the blood.
- Examples:
- Leptospira icterohaemorrhagica in the dog.
- Rift Valley fever virus.
- Some plant poisonings.
- Lantana.
- Some fungal infections.
- Aflatoxicosis.
Post-Hepatic (Obstructive) Icterus
- Due to the flow of bile being obstructed, for example by:
- Gallstones
- Parasites
- Ascaris suum in the bile ducts of pigs.
- Tumours
- Adenocarcinoma of pancreas presses upon and occludes the bile duct.
- Results in excessive conjugated bilirubin in the blood.
- Constructive icterus causes, out of the three types of icterus,
- The most elevated levels of bilirubin in the blood
- The greatest discoloration of the tissues of the body.
Van de Berg Test
- This test can distinguish between the different types of jaundice, based on whether the bilirubin is conjugated or not.
- Plasma from the jaundiced animal is treated with an aqueous solution of a reagent (diazotised sulphanilic acid).
- Gives a red-purple colour.
- The intensity of this colour is directly proportional to the amount of water-soluble (i.e. conjugated ) bilirubin in the sample.
- Further addition of alcohol intensifies the colour if there is non-water-soluble (i.e. unconjugated) bilirubin also present.
- The intensified colour is directly proportional to the total amount of bilirubin present in the sample.
- The difference between the two readings gives the amount of unconjugated bilirubin in the sample.
- Gives a red-purple colour.
Haematoidin
- Haematoidin is bile pigment laid down in areas of focal haemorrhage where red blood cells are lysed.
- I.e. it is unconjugated bilirubin in tissues.
- Has a clear yellow colour.
- Can sometimes be granular.
- Could be confused with haemosiderin.
- Unlike haemosiderin, haematoid does not contain iron.
- Does not stain with Prussian Blue.
- Unlike haemosiderin, haematoid does not contain iron.
- Could be confused with haemosiderin.
Porphyria
- Porphyrin is a component of haeme.
- Porphyria is a rare heritable condition in cattle, pigs and cats, where there is imperfect synthesis of porphyrin.
- Due to defective enzymes.
- Leads to a degree of anaemia in affected animals.
- Porphyria is best-documented in cattle.
- Porphyrins (brownish in colour) accumulate in bone, teeth and other internal tissues.
- Excess porphyrins also circulate in the blood stream and are excreted in the urine.
- Urine has a reddish colour.
- Porphyrin is a fluorescent pigment.
- Urine will also fluoresce under ultra-violet light.
Histological Appearance
- Brown granular pigment that looks like haemosiderin but is iron negative.
- Found in macrophages of bone marrow, liver, lungs, and lymph nodes.
Photosensitisation
- Porphyrin is a fluorescent pigment.
- Is related to chlorophyll.
- UV light acts on porphyrins as they circulate in the blood under the white skin.
- Changed to a longer wavelength.
- Causes acute inflammation in the skin.
- Changed to a longer wavelength.
- The inflammation caused may look like sunburn, but is actually a necrotising dermatitis.
- Affected areas slough off.
- Large areas of the dermis are exposed to infection.
- Death due to toxaemia can ensue if it is severe.
- Removing animals from sunlight causes the lesions to regress.
- The most common and important form of photosensitisation in animals is due to liver damage coupled with a diet containing a lot of chlorophyll.
- I. e. animals on green pasture.
- A wide variety of plants and fungi have been implicated in causing acute toxic damage to the liver.
- Including grasses, clovers and Brassica sp.
- This liver damage may cause the imperfect breakdown of chlorophyll and raised phyloerythrin levels.
- Causes photosensitisation.
- The common form in sheep is facial eczema.
- The face and head are swollen, raw and bleeding.
- A third form of photosensitisation occurs in the absence of liver damage and is due to certain plants containing excessive fluorescent pigments, e.g.
- Buckwheat (Fagopyrum esculentum)
- St. John’s wort (Hypericum perforatum)
Lipofuscin
- A yellow-brown granular pigment composed of lipid, phospholipid and protein polymers.
- Thought to be derived from the lipid peroxidation of cellular membranes.
- Lipofuscin is the ageing pigment.
- Can be seen in senile animals in
- Muscle
- E.g. in "brown atrophy".
- Myocardium
- Neurones (particularly those of horses)
- Normal liver of middle-aged cats.
- Muscle
- Can be seen in senile animals in
- Xanthosis is when lipofuscin is a prominent feature in the tissues of Ayrshire cattle.
- Lipofuscin is found in the heart, diaphragm, masseter muscles, kidney and adrenal cortex.
- Pathologically, lipofuscin is associated with Vitamin E/ Selenium deficiency.
- There is excessive lipid peroxidation of cellular membranes by free O2 radicals.
Gross Appearance
- Xanthosis - gives a brown colour to the organ.
- Senility
- May impart a brownish colour to the heart.
- Sometimes called ‘brown atrophy’.
- In other areas, lipofuscin is only visualised microscopically.
- May impart a brownish colour to the heart.
Histological Appearance
- Granular
- Brown- yellow in colour.
- Lies in the cytoplasm...
- ...At either end of the nucleus in the heart.
- ...Scattered throughout in the liver and neurones
Ceroid
- Is a variant of lipfuscin.
- Stains acid fast.
- Occurs in:
- Hepatocytes
- E.g. in choline deficiency in cirrhosis
- Macrophages
- A variety of tissues including fat, cardiac muscle, splenic trabeculae and intestine in Vitamin E deficiency.
- Sometimes being so prominent as to be grossly visible.
- Yellow fat disease
- Pigs and cats
- Brown gut
- Dogs
- Yellow fat disease
- Sometimes being so prominent as to be grossly visible.
- Hepatocytes