Lecture 19/20 4/11/24 Flashcards
What are exogenous pigments?
pigments formed outside the body
What are the characteristics of anthracosis?
-due to inhalation of carbon
-indicates inhalation of polluted air
-asymptomatic
What are the gross lesions associated with anthracosis?
-tiny gray-black specks throughout lung
-gray-black tracheobronchial lymph nodes; esp. medulla
What are the histopathologic lesions associated with anthracosis?
-irregular black particles within lung macrophages
-similar pigment within tracheobronchial lymph node macrophages
What are the characteristics of silicosis?
-due to inhalation of silica
-weight loss and exercise intolerance due to pulmonary fibrosis
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
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
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
How is melanin formed?
tyrosine is converted into dioxyphenylalanine via a copper-dependent tyrosinase
What is the histopathologic appearance of melanin?
regularly sized brown granules within cytoplasm
Where is melanin normally found?
epidermis
-hair
-hoof
-horn
-iris
-retina
What is the function of melanin?
protect against solar radiation
What does a lack of melanin predispose to?
skin cancer, such as squamous cell carcinoma
Which animals are predisposed to squamous cell carcinoma?
-white cats
-hereford cattle
-appaloosa and paint horses
What are the two main causes of hyperpigmentation?
-chronic sun exposure
-chronic irritation
What is melanosis?
congenital melanin pigmentation of unusual locations
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
