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4.27 Micro Lab III
By Dr. Barbeau
78
Pathology
Professional
04/27/2012

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Term
How long after innoculation is the acute HIV syndrome with wide dissemination of virus and seeding of lymphoid organs?
Definition
weeks 3-6
Term
What is the characteristic appearance of PCP on CXR?
Definition
bilateral fluffy pulmonary infiltrates, prominent in the hilum and base of the lungs
Term
What does a biopsy of PCP pneumonia look like?
Definition
eosinophilic frothy material; a combination of pneumocystis and plasma constituents present in many of the alveolar spaces
Term
What stain is used with pneumocystis jiroveci?
Definition
silver stain highlights the wall and central body of the organism
Term
What are the different ways to get a sample for PCP testing?
Definition
transbronchial biopsy, BAL, bronchial washing, induced sputum
Term
What are the lab tests done on sputum for PCP?
Definition
direct flourescent antibody (DFA) test (silver stains in some labs) NOT CULTURED!!!
Term
How is CMV transmitted?
Definition
close contact via bodily fluids
Term
What organs are commonly invovled by disseminated CMV in immunocompromised patients?
Definition
eyes (CMV retinitis), gut, kidneys, liver, pancreas, lungs, salivary glands, thyroid gland, adrenal gland, brain
Term
Describe the fundoscopic exam of a patient with CMV retinitis.
Definition
multiple retinal hemorrhages and regions of purulent exudate
Term
What would be seen on microscopy of CMV retinitis?
Definition
CMV inclusions
Term
What methods can be used for diagnosis of CMV?
Definition
PCR, serology (esp IgM), cell culture (esp rapid shell vials)
Term
How is CMV cultured?
Definition
in rapid shell vials; centrifuged to get CMV to enter cells more rapidly; read using immunoflourescence (flourescently labeled monoclonal antibodies)
Term
What virus can cause ulcers and pseudomembrane formation that resembles C diff colitis?
Definition
cytomegalovirus
Term
What causes the ulcers of a CMV infected colon to be green?
Definition
fecal material adherent to the ulcerated mucosa
Term
What causes ulceration of the colon in CMV infections?
Definition
infection of the vascular endothelium leading to thrombosis and necrosis of the colonic epithelium; also some direct cytotoxic effect of the epithelium by the CMV
Term
How do you diagnose CMV infection of the colon?
Definition
biopsy= pseudomembrane overlying a necrotic mucosa with viral inclusion characteristic of CMV in macrophages
Term
T/F CMV infect only cells of the immune system.
Definition
false; it infects many different cell types
Term
Why are CMV inclusions so unique?
Definition
CMV is able to produce intranuclear and intracytoplasmic inclusions
Term
What's the difference between CMV and C diff pseudomembranous colitis?
Definition
C diff associated pseudomembranes result from toxin-mediated destruction of the epithelium as well as ischemic necrosis secondary to thrombosis of underlying small vessels
Term
How do you test for C diff?
Definition
C diff antigen test for toxins A and B using EIA (ELISA)
Term
Describe the toxins of C difficile.
Definition
toxin A is an enterotoxin; b is a cytotoxin
Term
Is C diff cultured?
Definition
no; culture is outmoded
Term
Name some pathogens that commonly cause diarrhea in AIDS.
Definition
cryptosporidium, mycobacterium avium-intracellulare, cytomegalovirus, giardia, isospora belli
Term
What is the gross appearance of small bowel with a MAC infection?
Definition
nodular pattern the entire length of the small bowel
Term
What is the microscopic appearance of small intestine infected with MAC?
Definition
mycobacteria inside the histiocytes
Term
How do you test for intestinal MAC infection?
Definition
DO NOT CULTURE THE STOOL; biopsy and culture the biopsy specimen. This is because MAC is in the histiocytes in the laminopropia not in the stool
Term
How does MAC enteritis differ pathologically from cryptosporidiosis?
Definition
cryptosporidium is not invasive; the organisms attach to the superficial portions of the intestinal epithlium; MAC organims are found inside the histiocytes within the lamina propia and submucosa
Term
What is the best way to diagnose cryptosporidium?
Definition
giardia/cryptosporidium combined EIA performed on stool specimen
Term
What percent of patients with AIDS have clinical evidence of neurologic dysfunction?
Definition
30-50% of patients with AIDS develop some neurologic impairment during the course of their illness
Term
When addressing the issue of altered mental status in AIDS patients, there are two basic categories of diseases you could be dealing with:
Definition
1) primary HIV-associated syndromes
2) opportunistic diseases
Term
What is HIV encephalopathy?
Definition
areas of demyelination due to HIV neuroinvasion via infected monocytes, HIV virotoxins, and cellular activation/defense (cytokines)
Term
When during the course of HIV do patients get HIV encephalopathy?
Definition
can occur early-during seroconversion
Term
What is AIDS-related dimentia?
Definition
progressive decline in cognitive function with symptoms of memory loss and withdrawal and later global dementia
Term
When in the course of AIDS does AIDS-related dementia occur?
Definition
advanced AIDS when CD4 is less than 200 mm3
Term
An HIV positive patient with deep (subcortical) gray matter and white matter demyelination=
Definition
HIV encephalopathy
Term
What is the appearance of AIDS-related dementia under the microscope?
Definition
infiltrates of lymphocytes and macrophages, markedly elevated numbers of activated astrocytes, and hallmark=multinucleated giant cells
Term
What does CT scan of a brain with AIDS related dementia show?
Definition
widened sulci and expansion of cerebral ventricles: cerebral atrophy
Term
What are viral opportunistic CNS diseases?
Definition
CMV and progressive multifocal leukoencephalopathy
Term
What are some bacterial opportunistic CNS diseases?
Definition
tuberculosis and pyogenic bacterial infections
Term
What are some fungal opportunistic CNS diseases?
Definition
cryptococcus, histoplasmosis, coccidiomyocosis
Term
What are some parasitic opportunistic CNS processes?
Definition
toxoplasmosis
Term
What are some opportunistic neoplasms in the CNS?
Definition
CNS lymphomas both primary and metastatic (kaposi sarcoma is almost unheard of in the CNS)
Term
Demylination in HIV can be caused by...
Definition
HIV itself or PML
Term
What is the incidence of PML in AIDS?
Definition
1-6%
Term
What causes PML?
Definition
JC virus
Term
What is the pathophys of PML?
Definition
JC virus infects oligodendroglia directly, causing necrosis; demylination occurs in the infected areas
Term
What is the histological appearance of PML?
Definition
oligodendroglial nuclei: chromatin appears glassy, dark, and smudged
Term
MRI of PML shows...
Definition
multiple focal white matter lesions
Term
How do you diagnose PML?
Definition
PCR or CSF for JC virus (get radiologic evidence first!)
Term
What type of immunocompromised patient usually gets toxoplasmosis?
Definition
bone marrow transplant population
Term
What is the pathophys of toxoplasmosis infection in immunocompromised patients?
Definition
typically reactivation of a prior infection
Term
Describe the appearance of toxoplasma encephalitis under the microscope.
Definition
areas of necrosis infiltrated by reactive, rod-shaped, microglial cells; called microglial nodules
Term
How do you test for toxoplasma encephalitis?
Definition
test CSF for toxo using PCR (only appropriate if there are focal brain lesions on CT or MRI)
Term
What are sites most commonly involved by toxoplasma?
Definition
lung (pneumonitis), lymph nodes (lymphadenitis), choroid and retina (chorioretinitis) like CMV, and brain (encephalitis)
Term
Where does HSV go latent?
Definition
HSV-1 usually in the trigeminal ganglia; HSV-2 usually in the sacral ganglia
Term
HSV encephalitis typically is due to HSV latent in the _____.
Definition
trigeminal ganglia
Term
What area of the brain is affected by HSV encephalitis?
Definition
usually inferior and medial temporal lobes, sometimes frontal
Term
How does HSV injure neurons?
Definition
directly infects cells in the cerebral cortex causing necrosis and a glial reaction leading to lytic, hemorrhagic injury
Term
How do you diagnose HSV encephalitis?
Definition
PCR of the cerebrospinal fluid
Term
What is the appearance of HSV meningoencephalitis on microscopy?
Definition
inflammation in the meninges and the brain parenchyma; also hemorrhage surrounding the perivascular lymphocytic infiltrates; produces a glial nodule (similar to toxoplasma)
Term
Describe the CSF in HSV encephalitis?
Definition
typically mononuclear pleocytosis (50 to several hundred WBCs), RBC count usually elevated, protein levels increased (an exception from the general viral rule)
Term
How is HSV encephalitis diagnosed?
Definition
CSF cuture is INSENSITIVE and slwo so PCR of CSF to detect HSV DNA is the gold standard (brain biopsy was the old way)
Term
What type of imaging should you get for HSV encephalopathy?
Definition
brain MRI is more sensitive than CT; abnormalities are found in approximately 90% of HSV encephalitis. Localized temporal, sometimes frontal, abnormalities are classic
Term
What does EEG show for a patient with HSV encephalitis?
Definition
focal abnormalities of the temporal lobes
Term
If you have an AIDS patient with altered mental status but no focal lesions by CT scan or MRI you can rule out...
Definition
toxoplasmosis, CNS lymphoma, and abscess
Term
If you have a patient with AIDS presenting with altered mental status but they don't have focal white matter lesions on MRI you can rule out...
Definition
PML
Term
_____________ is an important treatable cause of altered mental status in immunocompromised patients and should be ruled out by a negative CSF ______ test.
Definition
cryptococcosis; CSF cryptococcal antigen test
Term
What quick stain should you use if you suspect a zygomyces?
Definition
lactophenol cotton blue
Term
Name the medially important zygomycetes.
Definition
mucor, rhizopus, absidia, Cunninghamella
Term
What is the classical linical presentaiton of a periorbital zygomycete infection?
Definition
unilateral proptosis
Term
How do you distinguish mucormycosis from aspergillus?
Definition
mucormycosis ahs long, aseptate, ribbon like hyphae; aspergillus has septae and 45 degree angle branching along with condiaphores
Term
What happens to sporangiospores that are inhaled?
Definition
they are cleared by phagocytosis-> macrophages kill intracellular spores by oxidative mechanisms; neutrophils damage fungal hyphae by extracellular means; in immunocompromised hosts, spores may survive phagocytosis and germinate
Term
What are the complications caused by fungal spores germinating in immunocompromised hosts?
Definition
hyphae invade the oral and sinus mucosa, invading blood vessels and causing thrombosis and tissue necrosis
Term
What diseases/medical situations cause predisposition to invasive disease by mucormycosis?
Definition
diabetes, steroid treatment, hematopoietic stem-cell transplants
Term
Why does diabetes, steroid therapy, etc. predispose patients to invasive fungal disease?
Definition
neutropenia and impaired phagocyte function
Term
What are the physical exam findings of invasive zygomycosis?
Definition
inflammation or tissue necrosis (black eschar) late in infection
Term
Definitive diagnosis of rhino-orbito-cerebral zygomycosis is based upon..
Definition
culture and/or histopathology
Term
How is invasive mucormycosis treated?
Definition
intravenous amphotericin B and extensive surgical debridement
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