Thyroid Pathology
eye infections
Lecture information
Lecturer
Kristine Krafts, M.D.
Elvis-obsessed.
Veni, vidi, volo in domum redire.*
Outline
• Introduction
• Orbit
• Eyelid
• Conjunctiva
• Cornea
• 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 inflammation of eyelid
chalazion lipogranuloma at eyelid margin (from an obstructed sebaceous gland which leaks lipids into surrounding tissue)
chorioretinitis inflammation of the retina extending into the choroid
conjunctivitis inflammation of the conjunctiva
dacryocystitis inflammation of lacrimal sac
endophthalmitis inflammation within the vitreous humor
episcleritis inflammation of the sclera
hordeolum focal inflammation of eyelid margin (also called stye)
hypopyon pus in the anterior chamber
keratitis inflammation of the cornea
keratoconjunctivitis extensive inflammation of conjunctiva and cornea
ophthalmia neonatorum conjunctivitis in neonate
panophthalmitis inflammation of retina, choroid, sclera, and orbit
uveitis inflammation of uveal tract (iris, ciliary body, choroid)
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
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
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)
Fungi
Mucor
• one of a group of fungi known as zygomycetes
• broad, ribbon-like, branching hyphae with almost no septae
• ubiquitous: soil, bread.
• 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
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
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
Parasites
Acanthamoeba
• amoeba
• found in soil and water
• organism infects cornea and sometimes brain
• 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
• protozoan
• definitive host: cat; intermediate hosts: humans, other animals
• transmitted through ingestion of raw, contaminated meat or through exposure to contaminated cat feces.
• disease can be congenital (malformations, chorioretinitis, stillbirth), infectious-mono-like (chills, fever, headache, lymphadenopathy), or disseminated in immunocompromised patients (pneumonitis, myocarditis, and encephalitis)
How to make a diagnosis
• 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)
Orbit
Orbital cellulitis
Organisms
• Typical oral/nasopharyngeal flora (e.g., Staphylococci)
• Mucor
Disease
• Because of the proximity of the sinuses to the orbit, uncontrolled sinus infections may spread to the orbit.
• The most devastating of these is mucormycosis, an uncommon rhinocerebral infection which occurs in patients with malignancies or diabetes
• Mucor is very invasive: goes right through sinuses to eyes and brain. It is rapidly fatal – so need to diagnose and treat quickly.
Diagnosis
• tissue biopsy
• cultures sometimes negative!
Eyelid
Styes
• 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.
Weird stuff
Trichinosis
• Organism: Trichinella spirosis
• Transmission: eating raw pork
• Symptoms: bilateral lid swelling
Chagas disease
• Organism: Trypanosoma cruzi
• Endemic areas: Central and South America
• 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.
• Symptoms: unilateral lid swelling
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.
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.[2] Most Chlamydial conjunctivitis in this country is “inclusion conjunctivitis” (due to serotypes D – K), which is not as serious as trachoma.
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
Transmission
• usually following trauma
• also seen in patients using extended-wear soft contacts
• Acanthamoeba likes home-made contact lens saline
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).[3]
• 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.
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.
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
-----------------------
* I came, I saw, I want to go home.
[1] Lots of things besides bugs can cause inflammation: chronic diseases like rheumatoid arthritis, allergic diseases, neoplasms, you name it.
[2] 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 population湩猠s in southwest US.
[3] 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.
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mucor
ribbon-like hyphae
Lots of infectious processes can affect the retina and/or choroid. Usually, infection of one goes along with infection of the other.
Mucormycosis in a man with diabetes
Endophthalmitis = infection of the vitreous humor.
Don't try to make your own saline solution.
Acanthamoeba
stellate cyst in corneal scraping
stye
Styes are usually caused by Staph aureus and are treated with hot packs.
Trypanosoma cruzi
CMV in lung
intranuclear and cytopasmic inclusions
Neisseria conjunctivitis is hyperpurulent.
Treat immediately to prevent blindness.
The orbit is just above the maxillary sinus and just lateral to the ethmoidal sinus.
Staphylococcus aureus
cocci in clusters
chlamydial inclusions
(Pap stain)
chlamydia conjunctivitis
candida
yeasts and hyphae
[pic][4]
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