2-25,26 - HSType1,4,1+4 Flashcards
Immune Privilege in the Eye
- Eye limits inflammation due to delicate, irreplacable tissue which when damaged, decreases vision.
Tissues are immune priviledged via:
- Lack of blood or lymph inside eye
- B-Aqeuous + B-Retinal barrier
- Immunosuppresive molecules e.g. TFG-beta2 and Fas ligand
Sympathetic ophthalmia
A.K.A. Spared eye injury
- When immune privilege is bypassed at the eye
- Rare bilateral granulomatous uvieitis
- Penetrating injurt to one eye -> intraocular inflammation -> immune system recognises antigens inside eye -> attacks both eyes due to type 4 hypersensitivity (T cell-mediated).
- Occurs sometime between 5 days or several years after injury in 1st eye
- Bilateral blindness if untreated.
Type 1 hypersensitivity
- Sensitisation = 1st contact, APC take allergen to present to T cell -> Thelper release IL molecules -> B cell become plasma -> IgE from plasma cells -> IgE binds to mast cells + basophils
- Effector= IgE + allergen -> mast cell degranulate -> inflamm mediators e.g. histamine, prostaglandins, leukotrienes
- Examples of hayfever, eczema, hives, asthma. Example of causes are food, drugs, or dust.
- 30min after allergen exposure causes effect.
Allergic conjunctivitis
- General information
- Signs + symptoms
Type 1 HS at conjunctiva
- Often due to pollen, animal dander, dust mites
- Systemic effects also common (e.g. ezcema, asthma, i.e. hayfever)
- Either seasonal (SAC) or perennial (PAC) (all year) or anaphylatic drug allergy
Symptoms:
- Bilateral (usually) itchy red eyes
- Itching
- General symptoms of allergy e.g. sneeze, rash
Signs:
- Conjuctival injection + papillae (follicles possible) + chemosis (swelling)
- Erthematous (red) + oedematous lids
- Watery discharge
Type 4 hypersensitivity
Delayed or cell-mediated
- Sensitisation = Allergen + APC -> Present to MHC -> T cell maturation
- Effector = T cell actvation -> response (helpers which release cytokines + cytotoxic which directly attacks)
- Examples: Poison ivy, hair dye, mantoux test
Allergic contact dermatitis
- General information
- Signs + symptoms
a.k.a. contact allergic blepharoconjuncdtivitis/dermatoconjunctivitis, periorbital contact dermatitis
- Non-infectious inflammation (common from eye drop preservatives)
- Type 4 HS
Signs/symptoms:
- Eczematous dermatitis
- Periorbital oedema, erythema, vesicles
- Skin lichenification (leathery + thick lids)
- Severe periocular + ocular itching w/ mucoid/mucopurulent discharge
Phlyctenulosis
- Type 4 HS
- Often from S. aureus proteins, but others possible
- Can associate w/ acne/ocular rosacea, asthma, other allergies
- Small pink-grey gelatinous nodules on bulbar conj. next to limbus
- Made of lymphocytes + plasma cells
- Injection surrounding conj. BVs
- Spontaneous resolution, but can reach over to cornea.
Type 4b hypersensitivity
Type 1 + 4 combined
- Type 4 gives more T cell meaning more cytokines which increases IgE to further type 1 (feedback)
- Chronic inflammation, elevated immune system.
Vernal keratoconjunctivitis
- General information
- Signs + symptoms
VKC
- Severe ocular allergy, less common
- Children + young adults
- Worse in spring/summer
- Associated w/ atopy (asthma, eczema, hay fever, etc.)
- Most cases less severe by late teens, 5% get AKC
Symptoms:
- Intense itch
- Lacrimation
- Photophobia
- Thick mucoid discharge
Signs:
- Macropapillae under lids w/ whitish inflamm infiltrate (cobblestone texture) -> coalesce to giant papillae
- Limbal papillae (white jelly-like nodules, can coalesce)
- Horner-trantas dots (degenerated eosinophils + epithelial debri)
Atopic keratocojunctivitis
- General information
- Signs + symptoms
AKC
- Rare, persistent, severe ocular allergy
- Adulthood onset
- Like VKC but more severe
- Worse in winter
- Usually alongside atopic dermatitis (eczema) and asthma
- Visually impaired
Signs:
- Lids severly red, scaling, thick oedema
- Creases around lids (demi-morgan folds due to increase rubbing -> increase thickness -> folds on itself)
- Panda eyes where lids darker
- Conj. similar to VKC, but can look white if more widespread
- Forniceal shortening (symblepharon when bulbar + tarsal merge)
- Corneal damaged from micropapillae cobblestone texture
- Corneal shield ulcers, white due to protein + fibrin leak onto ulcers + aggregation. Hunders regeneration.
- Limbal stem cell deficiency -> sub-epithelial fibrovascular ingrowth = corneal neovasc.
Giant papillary conjunctivitis
- Mechanically induced
- Not HS, inflammed tarsal conj.
- Any mechanical damage e.g. CL wear, ocular prosthetics, exposured sutures, mucous-fishing sysdrome (mucous producing disease causes Px to prode their eye), etc…
- Concurrent allergy makes worse
- Signs/symptoms similar to VKC/AKC
Type 2 hypersensitivity
Antibody-mediated cytotoxicity
- Sensitisation = Contact -> IgG/IgM from plasma -> antigen binds to cell (or already on cell) -> IgG + IgM circulation
- Effector = IgG/IgM-cell interaction -> phagocytosis, complement, Antibody-Dependent Cell-Mediated Cytotoxic reaction (ADCC)
- 3-6 hrs after exposure
- Often leads to autoimmune e.g. RF, or allergic reactions to blood transfusion or drugs e.g. penicillin.
Cicatricial pemphigoid
- General disease information
- Ocular involvement
- Diagnose how?
- Stages of ocular disease
A.K.A. Mucous membrane pemphigoid
- Rare, chronic, subepithelial blistering from autoimmune (blisters appear bullous so sometimes called “bullous pemphigoid)
- Type 2 HS. Binding of Basement Membrane Zone (BMZ) of epithelial tissue of mucous membranes
- Any mucousal surface affected.
- Usually older affected
61% of cases involve eye (most common involvement is mouth)
- Often misdiagnosed as dry eye
- Make sure to ask about lesions on other parts of body
- Diagnosis confirmed w/ immunoflourescence of biopsy (IgG,A,M, + C3 along BM of conj. epithelium)
Conj. Early stage:
- Non-specific recurrent/chronic bilateral papillary conjunctivitis (presentation may be unilateral at first)
Conj. Intermediate:
- Forniceal shortening + symblepharon (due to scar -> traction)
- Caruncle keratinisation
Conj. End:
- Severe conjunctival fibrosis + symblepharon + ankylobepharon (eyelids merge)
Corneal:
- Dry eye (epithelial staining)
- If infect, gigantic ulcer + neovasc
- Keratinisation + fibrosis –> opaque
Type 3 hypersensitivity
Immune complex-mediated
- Sensitisation = Contact -> Ab production -> Ab + Ag = immune complexes
- Effector = If Ag:Ab roughly equal, larger immune complexes form -> if unclearable -> damage
- e.g. SLE, RA, serum sickness
Sjorgren’s syndrome
- General information
- Signs + symptoms for both ocular and non-ocular effects
- Exocrine glands affected by type 3 HS (notably salivary and lacrimal glands)
- Mainly affects women in 50s
- Both primary or secondary
- Associated risk towards malignant non-Hodgkin lymphoma (excess lymphocyte)
Dry eyes generic symptoms - Aqeuous deficient
- grit + burn + FB sensation
- transient blur
- Redness + crusting eyelids
- Worse at end of day or exposure to something that evaporates tears e.g. computer, wind
Dry eye signs/tests:
- Reduced tear meniscus height (<0.25mm)
- Prominent mucous debri (as not enough aqueous)
- Punctate Epithelial Erosions
- TBUT (<10s), Schirmer (<10 if no anaesthetic, <6 if w/), Phenol red thread (<6s)
Other signs/symptoms:
- Dry mouth (dry fissured tongue, oral candida more likely, hard to eat dry food or talk for long)
- Dry skin (Reduced sweating)
