Download Thyroid Pathology

eye infections
Lecture information
Lecturer
Kristine Krafts, M.D.
Elvis-obsessed.
Veni, vidi, volo in domum redire.*
Outline
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Introduction
Orbit
Eyelid
Conjunctiva
Cornea
Retina
I came, I saw, I want to go home.
eye infections | 2 of 11
intro | orbit | eyelid | conjunctiva | cornea | uvea | retina
Introduction
Eye anatomy
Robbins, fig. 29-1
How to think about an eye infection
1. By anatomic compartment.
2. By age of patient.
3. By offending bug.
4. Remember: not every inflammatory process in the eye is caused by an organism!1
Clinical terms
blepharitis
chalazion
chorioretinitis
conjunctivitis
dacryocystitis
endophthalmitis
episcleritis
hordeolum
hypopyon
keratitis
keratoconjunctivitis
ophthalmia neonatorum
panophthalmitis
uveitis
inflammation of eyelid
lipogranuloma at eyelid margin (from an obstructed sebaceous gland which
leaks lipids into surrounding tissue)
inflammation of the retina extending into the choroid
inflammation of the conjunctiva
inflammation of lacrimal sac
inflammation within the vitreous humor
inflammation of the sclera
focal inflammation of eyelid margin (also called stye)
pus in the anterior chamber
inflammation of the cornea
extensive inflammation of conjunctiva and cornea
conjunctivitis in neonate
inflammation of retina, choroid, sclera, and orbit
inflammation of uveal tract (iris, ciliary body, choroid)
Lots of things besides bugs can cause inflammation: chronic diseases like rheumatoid arthritis, allergic diseases,
neoplasms, you name it.
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eye infections | 3 of 11
intro | orbit | eyelid | conjunctiva | cornea | uvea | retina
Infectious agents
Bacteria
Staphylococcus aureus
 gram-positive cocci in clusters
 catalase positive, coagulase positive
 part of normal flora of skin, nose
Streptococcus pneumoniae
 gram positive diplococci
 catalase negative
 alpha-hemolytic
 encapsulated
Propionibacterium acnes
 gram-positive rod
 causes acne
Staphylococcus aureus
cocci in clusters
Neisseria gonorrhoeae
 gram-negative diplococcus
 oxidase positive
 common STD
Haemophilus influenzae
 gram-negative rod
 fastidious organism (to culture H. influenzae, need to use chocolate agar,
which has X and V factors in it)
Chlamydia trachomatis
 obligate intracellular bacterium (can't make own ATP)
 too small to be seen on gram stain
 "elementary body" – infective form (sporelike, extracellular structure)
 "reticulate body" – replicating form (intracellular)
 very common – and often undiagnosed – sexually-transmitted disease (STD)
 can't diagnose on gram stain – so, look for Chlamydia antigen (in serum) or do
a conjunctival scraping and stain it with Papanicolou stain (to look for
characteristic chlamydial inclusions – really just enlarged endosomes!)
Pseudomonas aeruginosa
 gram-negative rod
 oxidase positive
 smells fruity (in lab, and sometimes in patient!)
 may make pigments (e.g., fluorescein) – pus may be fluorescent (or, under
regular room light, may look bluish)
 ubiquitous (lives in soil and water)
 often drug-resistant
chlamydial inclusions
(Pap stain)
Mycobacterium tuberculosis and avium
 gram-positive rod
 hard to stain with gram stain because of waxy cell wall! Acid-fast stains work.
 M. tuberculosis causes tuberculosis (no, really?)
 M. avium infection is more common in already-immunocompromised patients
(like patients with AIDS)
eye infections | 4 of 11
intro | orbit | eyelid | conjunctiva | cornea | uvea | retina
Fungi
Mucor
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one of a group of fungi known as zygomycetes
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broad, ribbon-like, branching hyphae with almost no septae
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ubiquitous: soil, bread.
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devastatingly destructive in immunocompromised patients
Candida
 dimorphic fungus: (1) yeast (little round things) and (2) hyphae
(including both true hyphae and pseudohyphae, which are long
buds that look like hyphae).
 part of normal skin, mucous membrane flora
 some species are drug-resistant
mucor
ribbon-like hyphae
Aspergillus
 branching, septate hyphae
 usual site of infection: lung
 destructive (grows right through blood vessels)
Pneumocystis carinii
 Little cup-shaped organisms
 Common in immunocompromised patients (especially patients with AIDS)
 Usual site of infection: lung
candida
yeasts and hyphae
Viruses
Adenovirus
 double stranded DNA virus
 family: Adenoviridae
 usual diseases: upper and lower respiratory tract infections, diarrhea,
conjunctivitis
 diagnosis: tissue culture
Cytomegalovirus
 double stranded DNA virus
 family: Herpesviridae
 usual disease: Cytomegalic inclusion disease
 infected cells are big, and show a big pink nuclear inclusion and smaller
basophilic cytoplasmic inclusions
 diagnosis: tissue culture, characteristic inclusions in cells
Herpes simplex virus
 double stranded DNA virus
 family: Herpesviridae
 usual diseases: cold sores, genital herpes
 infected cells are big, and show big intranuclear inclusions surrounded
by clear halos
 diagnosis: tissue culture, characteristic inclusions in cells
CMV in lung
intranuclear and cytopasmic inclusions
eye infections | 5 of 11
intro | orbit | eyelid | conjunctiva | cornea | uvea | retina
Parasites
Acanthamoeba
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amoeba
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found in soil and water
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organism infects cornea and sometimes brain
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prolonged course; usually fatal
Onchocerca volvulus
 nematode
 endemic areas: Africa, South America, Yemen
 vector: black fly
 disease (river blindness) involves chronic pruritic dermatitis and blindness
Trichinella spirosis
 nematode
 uncommon in US now because of strict laws requiring cooking of hog food
 transmitted through ingestion of raw, contaminated pork (pigs get infected by
eating infected rats or pork food products)
 organisms love striated muscle (including the extraocular muscles), but also
infect the heart and the CNS.
 organisms often evoke marked eosinophilia.
Trypanosoma cruzi
 protozoan
 endemic area: South America (rarely occurs in US, Mexico)
 transmitted by "kissing bug" that hides in cracks of loosely constructed houses
 bug bites sleeping inhabitant and leaves little infectious poopy nearby
 human scratches bite and infected poopy gets inside
 organisms cause cardiac and sometimes gastrointestinal damage.
Toxoplasma gondii
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protozoan
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definitive host: cat; intermediate hosts: humans, other animals
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transmitted through ingestion of raw, contaminated meat or through exposure
to contaminated cat feces.
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disease can be congenital (malformations, chorioretinitis, stillbirth), infectiousmono-like (chills, fever, headache, lymphadenopathy), or disseminated in
immunocompromised patients (pneumonitis, myocarditis, and encephalitis)
Trypanosoma cruzi
How to make a diagnosis
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Look at conjunctiva, sclera (red? edematous? discharge?)
Look at exudate (if there is one): pus (with PMNs) in bacterial infections, more
watery (with lymphocytes) in viral infections, very watery (with eosinophils) in
allergic reactions.
Slit-lamp examination (to get a good, magnified look inside eye)
Corneal scrapings for gram stain, fungal stains, bacterial/fungal/viral culture.
Deeper infections require special techniques (e.g., removal of vitreous humor)
Serology and blood cultures are occasionally helpful (in systemic diseases like
Toxoplasmosis and Candida sepsis)
eye infections | 6 of 11
intro | orbit | eyelid | conjunctiva | cornea | uvea | retina
Orbit
Orbital cellulitis
Organisms
 Typical oral/nasopharyngeal flora (e.g., Staphylococci)
 Mucor
Disease
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Because of the proximity of the sinuses to the orbit, uncontrolled sinus
infections may spread to the orbit.
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The most devastating of these is mucormycosis, an uncommon rhinocerebral
infection which occurs in patients with malignancies or diabetes
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Mucor is very invasive: goes right through sinuses to eyes and brain. It is
rapidly fatal – so need to diagnose and treat quickly.
Diagnosis
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tissue biopsy
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cultures sometimes negative!
The orbit is just above the
maxillary sinus and just lateral
to the ethmoidal sinus.
Mucormycosis in a man with diabetes
eye infections | 7 of 11
intro | orbit | eyelid | conjunctiva | cornea | uvea | retina
Eyelid
Styes
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Organisms: Staphylococcus aureus, Propionibacterium acnes
Disease: infection of glands at base of eyelid causing a hot, red, painful
nodule.
Treatment: warm packs, topical antibiotics if necessary.
Styes are usually caused by
Staph aureus and are treated
with hot packs.
Weird stuff
Trichinosis
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Organism: Trichinella spirosis
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Transmission: eating raw pork
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Symptoms: bilateral lid swelling
Chagas disease
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Organism: Trypanosoma cruzi
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Endemic areas: Central and South America
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Transmission: Reduviidae ("kissing") bug, infected with T. cruzi, bites
human on face then turns around and chagas right on the bite; human
scratches infected T. cruzi poopy into skin/eye.
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Symptoms: unilateral lid swelling
stye
eye infections | 8 of 11
intro | orbit | eyelid | conjunctiva | cornea | uvea | retina
Conjunctiva
Neonatal conjunctivitis
Organisms
 Chlamydia trachomatis (serotypes D-K)
 Neisseria gonorrhoeae
 Staphylococcus aureus
Transmission
 passage through infected birth canal (Chlamydia, Neisseria)
 person-to-person contact (S. aureus)
 All babies get silver nitrate and erythromycin in eyes after birth.
 If done correctly, this prevents Neisseria infection (Chlamydia and S. aureus
infections are decreased but not prevented).
Disease
 Chlamydia: conjunctival redness and eyelid edema with somewhat purulent
discharge starting about 1 week after birth. Although Chlamydial conjunctivitis
usually responds to topical antibiotics, the infection can be associated with
pneumonia, otitis media, and gastrointestinal complications, so systemic
antibiotics may be necessary.
 Neisseria: acute onset of abundant yellow-green, purulent discharge starting a
few days after birth. Rapidly causes severe corneal ulceration, perforation, and
blindness. Baby, mom and dad need immediate, systemic antibiotics because
of the grave consequences.
 Staph aureus: "sticky eye" (crusty, sticky discharge); complications rare.
Neisseria conjunctivitis is
hyperpurulent.
Treat immediately to prevent
blindness.
Post-neonatal conjunctivitis
Organisms
 Streptococcus pneumoniae
 Staphylococcus aureus
 Haemophilus influenzae
 Chlamydia trachomatis (serotypes A-C or serotypes D-K, see below)
 Herpes simplex
 Adenovirus
Transmission
 direct contact (fingers); eyedroppers; towels; swimming pools
 respiratory droplet (S. pneumoniae)
 sexual transmission (C. trachomatis)
Disease
 symptoms: bilateral redness, pain, itching.
 signs: purulent discharge (if infection is bacterial) or not-very-purulent discharge (if
infection is viral)
 Many cases resolve in a couple weeks with no sequelae.
 The big bad exception: Trachoma (Chlamydial conjunctivitis due to serotypes A
through C), which can cause blindness.1 Most Chlamydial conjunctivitis in this
country is “inclusion conjunctivitis” (due to serotypes D – K), which is not as
serious as trachoma.
chlamydia conjunctivitis
Chlamydia trachomatis (serotypes A – C) can cause conjunctival scarring → decreased mucin secretion from conjunctival
goblet cells → decreased adherence of tears to cornea → corneal ulceration, scarring and blindness. It is a big cause of
blindness in developing areas of Asia and Africa; also seen in Native American populations in southwest US.
1
eye infections | 9 of 11
intro | orbit | eyelid | conjunctiva | cornea | retina
Cornea
Keratitis and corneal ulceration
Organisms
 Pseudomonas aeruginosa
 conjunctivitis-causing bugs (Streptococcus pneumoniae, Staphylococcus aureus
Haemophilus influenzae, Chlamydia trachomatis)
 Aspergillus
 Herpes simplex and zoster
 Acanthamoeba
Acanthamoeba
Transmission
stellate cyst in corneal scraping
 usually following trauma
 also seen in patients using extended-wear soft contacts
Don't try to make your own
 Acanthamoeba likes home-made contact lens saline
saline solution.
Disease
 Infection of the cornea causes dissolution of the corneal stroma, and eventually
thinning and scarring of the cornea.
 Worse, vessels in ciliary body and iris become leaky, and cells and exudate
accumulate in anterior chamber ("hypopyon": pus in anterior chamber).1
 Pus in the anterior chamber can lead to adhesions between iris and cornea
(anterior synechiae) or iris and anterior lens surface (posterior synechiae).
Anterior synechiae can lead to increased intraocular pressure and optic
nerve damage.
Sometimes the inflammatory cells adhere to the cornea, producing "keratic
precipitates," the size and shape of which can give clues as to the underlying cause of
the inflammation.
1
eye infections | 10 of 11
intro | orbit | eyelid | conjunctiva | cornea | retina
Retina, choroid and vitreous humor
Chorioretinitis
Organisms
 Toxoplasma gondii
 Cytomegalovirus (CMV)
 Pneumocystis carinii
 Mycobacterium avium
 Candida
 Onchocerca volvulus
Transmission
 Trans-placental (Toxoplasma, CMV)
 Hematogenous (Candida can spread to choroid/retina from IV drug abuse or
from candida sepsis due to other causes.)
 Vector (Onchocerca, endemic in Central America and tropical Africa, is
transmitted through the bite of an infected black fly.)
Disease
 Symptoms: if unilateral, the patient may squint or favor the unaffected eye.
Photophobia and/or clumsiness (due to decreased vision) can occur.
 Untreated, chorioretinitis can lead to partial or total loss of vision.
 Onchocerca is different! Microfilariae (tiny worms) develop in subcutaneous
nodules, then migrate through skin (causing dermatitis, loss of elasticity) and
eye (causing blindness – "river blindness"). Eye lesions begin as keratitis, and
extend to anterior chamber, choroid and retina.
Lots of infectious processes can
affect the retina and/or choroid.
Usually, infection of one goes
along with infection of the
other.
Endophthalmitis
Organisms
 Candida
 Lots of bacteria, including: Staphylococcus aureus, Streptococci, and Pseudomonas
Transmission
 Endogenous: transmitted through hematogenous routes (most of these cases
are due to fungal infections, particularly Candida)
 Exogenous: transmitted by blunt trauma, or by extension of pre-existing
keratitis or uveitis (these cases can be caused by many different bacteria,
including Staphylococcus aureus, Streptococci, and Pseudomonas).
Disease
 The term "endophthalmitis" is only applied when there is pus within the
vitreous humor (not just pus in the anterior chamber).
 The retina (which lines the vitreous cavity) is very sensitive to pus; after even a
few hours of exposure, the retina may be irreversibly damaged.
 Endophthalmitis often leads to blindness even when treated aggressively
Endophthalmitis = infection of the
vitreous humor.
Once an infectious process
reaches the vitreous humor, it can
cause irreversible retinal damage
in a matter of hours.
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