Overview of Disease Mechanisms in the Eye

Overview of Disease Mechanisms in the Eye

Christopher M Reilly, DVM, MAS, DACVP Basic Science Course June 7‐8, 2016 NC State University * Outline • Tips on pathology submissions • General processes and definitions – Congenital/developmental – Inflammatory – Atrophic, dysplastic – Neoplastic • Stains (may not get to, but for your reference) Submission

• Communication with your pathologist is key, regardless of who it is • A little advanced planning can go a long way Submission

• History, history, history – SIGNALMENT – SIGNS, clinical diagnosis/Ddx – DURATION – Prior treatment – LOCATION (if known, if applicable) Submission

• If using big labs, ask ahead – Some have eye‐interested and/or trained pathologists – Your clinic may already have a preference • If ancillary diagnostics expected (frozen section IHC, EM, PCR) plan ahead – Prep client with flexible estimate – Formalin is not always appropriate Submission

• For best results: – Remove adnexa/muscles MOST of the time, except • Complex orbital margins • Fornicial region is of interest – Can submit adnexal tissues separately • Indicate that they are to be examined – Inking of complex margins can help Developmental/Congenital/Genetic

• NOT synonymous – e.g. goniodysgenesis, POAG, etc. • Proper history can be essential – e.g. Anterior chamber collapse v. anterior segment dysgenesis • Dystrophies (e.g. corneal) – Genetically determined, but late onset Cellular Degeneration

• Injury can be lethal or sublethal – Reversible or adaptive (sublethal) • Not unique to the eye • Occur in some unique patterns – Ocular anatomy – Physiology Intracellular accumulations

• Intracellular edema – Formerly hydropic degeneration – Now “acute cellular swelling” or oncosis if severe – e.g. corneal epithelium, osmotic cataract • Typically reversible, unless severe Corneal Epithelial Edema Intracellular accumulation

• Other stuff – Lipid (lipid corneal dystrophy) • Also extracellular – Hemosiderin (chronic/resolving hemorrhage) – Lipofuscin (age, storage diseases, e.g. neuronal lipofuscinosis) Hemosiderin

Hematoidin Extracellular Accumulations

• Edema • Generally clear space – Uvea, retina, orbital tissues, dermis/lids • Cornea ‐ unique appearance of edema • Overhydration of GAGs between collagen fibers = “washed out” appearance of expected artifactual corneal clefting • When severe, fibers are wispy, irregular, and variably stained Normal Canine Cornea Corneal Edema Mineralization

• Dystrophic – Due to cell death, normal calcium • Metastatic – Hypercalcemia, normal tissue • Mineral is basophilic in tissue section – Often shatters/fragments with sectioning Stromal/BM mineralization

“Band Keratopathy” Von Kossa Stain Lethal Cellular Degeneration

• Necrobiosis – Normal death of cells as part of development – Keratinization, lens fiber senescence • Typically unnoticed (i.e. normal) Necrosis

• Cellular swelling ‐ oncosis – Hypereosinophilia ‐ denatured protein – Nuclear changes – karyorrhexis • Eventual loss of nuclear detail – Secondary inflammation • Tough call in single cells – Overlap with apoptosis, etc Necrosis ‐ retina

More viable

Necrotic Necrosis ‐ cornea • Can’t occur to extracellular matrix (ECM) • CAN occur in stromal tissue Apoptosis

• Programmed cell death • Can also be part of development – Anterior segment, lymphoid development • Intrinsic or extrinsic signals • Classically: shrunken cells with uniform nuclear fragmentation/pyknosis • No overt inflammation Apoptotic keratinocytes

www.studyblue.com Tissue Degeneration

• Atrophy –loss of tissue bulk – Senile iris atrophy – Optic nerve atrophy –often with gliosis – Phthisis bulbi – widespread along with disorganization Corpora Nigra Atrophic Corpora Nigra Optic nerve atrophy Phthisis bulbi

• The end stage of severe ocular dz • Must be differentiated from microphthalmia • Criteria: – Shrinkage – Atrophy – Disorganization Phthisis bulbi Phthisis, Cat Phthisis bulbi, cat Phthisis, cat Inflammation

• Can affect any or all of the eye • Classified by: – Location – Chronicity – Cell type(s) – Etiologies Other Solar Elastosis Apoptotic squamous cell (sunburn cell) Inflammation • Includes both the fluid (edema, flare) and cellular (infiltrate, cell) events – Corneal edema can be non‐inflammatory (endothelial disease) – Fluid dysregulation, however, may lead to inflammatory changes • Most eye diseases have some inflammatory or immune component Types

• Neutrophilic – Acute, innate – Tissue destruction, necrosis • keratomalacia – Cavities/chambers – Surfaces

https://bcrc.bio.umass.edu/courses/fall2011/biol/biol523/content/neutrophil Lymphocytic plasmacytic

• Chronic, adaptive – At least a couple days – Tissue response (e.g. uvea) • Often perivascular, sometimes nodular • Etiologically nonspecific – Proportion can help (plasma cells in FIP) Lymph/plasma cell/Mott cell Eosinophilic

• Acute or chronic • Allergy, foreign body, parasites • Immune/idiopathic – Eosinophilic keratitis • Grossly characteristic – Granular on corneal surface • Luna’s stain can highlight Luna’s Stain, Eos Granulomatous

• Variably strict definitions – True granulomas – Granulomatous inflammation –sheets • Plump, activated, interdigitated – Histiocytic infiltrates • Idiopathic/Immune mediated histiocytoses – Common, confusing, poorly understood Granulomatous

• Search for etiology – Fungal –stains: GMS, PAS, BCG IHC – Mycobacterial ‐ Fite’s, Ziehl‐Neelsen AF, BCG – Foreign body ‐ polarized light for plants, plastic, suture, hairs, cotton • Wrong diagnosis = wrong treatment – Steroids v antimicrobials • May need fresh tissue for culture – Think before you fix Granuloma Fibrosis

• Common end result of inflammation • Indicates chronicity • Corneal fibrosis/scarring • Uvea is resistant – But chambers and surfaces prone • Pre‐iridal, cyclitic, retrocorneal, vitreal, epiretinal – Often associated with prominent vessels Corneal Fibrosis Dystrophy

• Inherited*, non‐inflammatory, bilateral lesions – Corneal opacities in vet med • Endothelial dystrophy – Better characterized in humans –Boston Terriers, Dachshunds, Chihuahuas • Often secondary –true dystrophy? The ‘plasias • Aplasia – complete failure to form – Ocular agenesis – Segmental: coloboma • Hypoplasia – failure to reach normal size – Microophthalmia – Optic nerve hypoplasia • Hyperplasia –non‐neoplastic proliferation of cells – Corneal epithelial hyperplasia – v hyperTROPHY – increase in the size of individual cells • RPE hypertrophy with detachment The ‘plasias • Dysplasia – abnormal development – Retinal dysplasia – Goniodysgenesis • Metaplasia – transdifferentiation to another cell type – Osseous metaplasia – Epithelial‐mesenchymal transition – Squamous metaplasia of conjunctiva (vitamin A) • Neoplasia – unregulated growth of cells – Benign or malignant Neoplasia

• Round cell: leukocytes (melanoma?) – Sheets – No real pattern, architecture • Epithelial – polygonal, cuboidal, columnar – Nests, cords, tubules, acini, “islands” • Mesenchymal – spindle cells, mostly – More vague patterns, streams, whorls, etc Aging

• Variably significant, can be subtle – Nuclear sclerosis, senile cataract – Thickening of DM and lens capsule – Hyaline material in ciliary body – Cystic degeneration of neuroepithelia – Asteroid hyalosis Asteroid Hyalosis, dog Ciliary Hyalinization Systemic Disease

• Metabolic – Diabetes mellitus (cataract, uveitis) – Hypertension (retinal hemorrhage, etc) • Neoplasia – Metastasis • Infection – FIP, systemic mycoses, West Nile Virus Questions? Common Special Stains I

• Periodic Acid‐Schiff – Starch (glycogen, glycoproteins, fungi) – Magenta • Alcian Blue (Alb) – Mucopolysaccharides, GAGs – Bright blue • i.e. vitreous • Along with PAS – Deep Blue ‐ Cartilage Common Special Stains PAS-positive vascular deposits in diabetic vasculopathy • Periodic Acid‐Schiff ‐ PAS – Carbohydrates (BM, fungus, cellular debris, mucus, Lipofuscin) – Magenta – Often done w/ Alcian Blue • Grocott’s Methenamine Silver ‐ GMS – Similar to PAS, can stain differently – Black –can be confusing in pigmented eyes – Light green counterstain Neurnal Ceroid Lipofuscinosis

H&E Neuronal Ceroid Lipofuscinosis

PAS Common Special Stains II

• Tissue Gram stain – Typically Brown & Brenn (B&B) • Gram +, Gram –(often weak) • Yellow background • Other techniques better for some – Brown and Hopps for Klebsiella spp. B&B Tissue Gram Stain Common Special Stains III

• Von Kossa – Phosphate, black • Prussian Blue (or Gomori’s, Perl’s) – Iron (hemosiderin) • Masson’s Trichrome – Muscle = red; Collagen = Blue; Cytoplasm = Pink; Nuclei = Blue/black Von Kossa Stain Optic nerve, Trichrome Common Special Stains III

• Luna’s Stain – eosinophil granules – Red/brown • Giemsa/Toluidine blue – metachromatic – Mast cells (purple) – Bacteria (pink) Luna’s Stain, Eos Giemsa Common Special Stains IV

• Fontana Masson –Melanin – Black in a VERY pale background • Mucicarmine – Mucus – Pink, can highlight Cryptococcus • Acid Fast (Ziehl‐Neelson, Fite’s) – Mycobacteria, other Acid Fast – Red wblue background – Fite’s for atypical AFB (e.g. M. leprae) Mucicarmine Special Stains V

• Oil Red O, Sudan Black – Lipid, can’t be on processed tissue – Can do fixed, unprocessed • Phosphatongstic acid‐hematoxylin – Fibrin, black • Vierhoff‐van Gieson – Elastin, black Special Stains VI

• Luxol Fast Blue – Myelin, blue • Bodian’s – Axons, black • Combos: – LFB/HE, LFB/Bodians, LFB/PAS Luxol Fast Blue ‐ Myelin