Lecture 19/20 4/11/24 Flashcards by Danika Boltz

What are exogenous pigments?

pigments formed outside the body

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What are the characteristics of anthracosis?

-due to inhalation of carbon
-indicates inhalation of polluted air
-asymptomatic

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What are the gross lesions associated with anthracosis?

-tiny gray-black specks throughout lung
-gray-black tracheobronchial lymph nodes; esp. medulla

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What are the histopathologic lesions associated with anthracosis?

-irregular black particles within lung macrophages
-similar pigment within tracheobronchial lymph node macrophages

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What are the characteristics of silicosis?

-due to inhalation of silica
-weight loss and exercise intolerance due to pulmonary fibrosis

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What are the characteristics of tattoo ink?

-injected into dermis and taken up by resident macrophages
-macrophages can migrate to regional lymph nodes and pigment them

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What are the characteristics of carotenoids?

-fat soluble pigments of plant origin
-examples include carotene, xanthophyll, and chlorophyll
-normally present within adipose tissue of horses, primates, poultry, and certain cattle breeds

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What are the general characteristics of melanin?

-formed by melanocytes
-transferred to epithelial cells
-can be engulfed by macrophages and drained to local lymph nodes

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How is melanin formed?

tyrosine is converted into dioxyphenylalanine via a copper-dependent tyrosinase

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What is the histopathologic appearance of melanin?

regularly sized brown granules within cytoplasm

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Where is melanin normally found?

epidermis
-hair
-hoof
-horn
-iris
-retina

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What is the function of melanin?

protect against solar radiation

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What does a lack of melanin predispose to?

skin cancer, such as squamous cell carcinoma

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Which animals are predisposed to squamous cell carcinoma?

-white cats
-hereford cattle
-appaloosa and paint horses

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What are the two main causes of hyperpigmentation?

-chronic sun exposure
-chronic irritation

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What is melanosis?

congenital melanin pigmentation of unusual locations

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Where does melanosis occur in different species?

-ruminants: rostral meninges, esophagus, aorta
-pigs: mammary glands, lung, liver
-dogs: oral cavity, draining lymph nodes
-cats: nose, lips, eyelids
-birds/reptiles/amphibians: testes, ovaries, serosal surfaces

What leads to pseudomelanosis?

interaction between iron and bacteria

What is the main characteristic of malignant melanoma?

not associated with sun exposure in animals

What are the characteristics of malignant melanoma in dogs?

-found in the oral cavity and on the digits
-can be unpigmented

What are the characteristics of malignant melanoma in horses?

-predisposed sites are perineum, genitalia, parotid salivary gland
-nearly always begin benign; majority will undergo malignant transformation
-gene that causes horses to turn gray predisposes to melanoma

What are the characteristics of melanocytoma?

-benign melanoma
-common on haired skin of dogs
-congenital in swine, cattle, occasionally horses

What are the types of congenital insufficient melanin?

-albinism/hereditary lack of tyrosinase
-piebaldism/congenital multifocal lack of pigment

What are the types of acquired insufficient melanin?

-copper deficiency
-injury to skin

What are the characteristics of hemoglobin?

-red pigment within erythrocytes -postmortem red staining with hemoglobin is hemoglobin imbibition

What is hemosiderin?

brown storage form of iron from breakdown of RBCs; stored within macrophages

What is hemomelasma ilei?

grossly black, slightly raised serosal accumulation of hemosiderin on equine ileum

What are the characteristics of splenic capsular plaques?

-commonly occur on the margins of adult canine spleens -no clinical significance -composed of fibrosis, mineral, hemosiderin

What are the characteristics of bilirubin?

-constantly formed from breakdown of RBCs -circulates in blood in unconjugated form; unable to be secreted -conjugation occurs in liver; conjugated form is excreted in bile

What are the characteristics of icterus?

-accumulation of bilirubin in blood and tissues -tissues are grossly yellow; cannot see bilirubin microscopically

What are the classifications for icterus causes?

-prehepatic: due to excess breakdown of RBCs -hepatic: any liver disease that interferes with conjugation -posthepatic: obstruction of outflow of bile from liver

Which animals lack biliverdin reductase and are unable to develop icterus?

most birds

What are the characteristics of lipofuscin?

-breakdown product of lipid peroxidation of cellular membranes -"wear and tear" or aging pigments -finely granular golden pigment within the cytoplasm -commonly seen in myocardium, neurons, feline hepatocytes -not visible grossly

What are the characteristics of ceroid?

-breakdown product of lipid -seen in cases of vitamin E deficiency -grossly and histologically looks yellow

What are the characteristics of porphyrins?

-photodynamic pigments which produce free radicals when exposed to sunlight -cause photosensitization/damage to unpigmented skin

What are the characteristics of primary photosensitization (type 1)?

-caused by ingestion of photodynamic pigment -plants and drugs most common source -reversible if offending agent is removed

What are the characteristics of congenital porphyria (type 2)?

-rare inborn metabolic defect in synthesis of normal heme pigment -bones, teeth, and urine are red-brown and autofluorescent

What are the characteristics of hepatogenous photosensitization?

-chlorophyll is broken down into phylloerythrin, a photodynamic pigment which is normally removed by the liver -damaged liver cannot remove phylloerythrin -only a problem in herbivores

What is the pathogenesis of hepatogenous photosensitization?

-severe liver disease prevents liver from removing phylloerythrin -phylloerythrin in blood is exposed to sunlight in unpigmented/sparsely haired skin -production of free radicals leads to severe skin damage

Which types of photosensitization can be caused by toxic plants?

-primary -hepatogenous