Infectious Flashcards
what are the 3 things you can test for when doing mycobacterial molecular testing?
16S rRNA gene
hsp65
IS6110
what are the advantages of each mycobacterial molecular test?
16S is highly conserved
hsp65 is less susceptible to interference from formalin
IS6110 is more sensitive cp to non-tuberculous mycobacteria
what ihc should you use for leprosy
Fite-Faraco
Fungal wall components that you test for
Galactomannan
(1,3) beta-D-glucan (not in mucorales)
Instead of 18S, what are more labs using for fungal sequencing targets?
ITS (internal transcribed spacer)
D1/D2
what causes SSPE subacute sclerosis panencephalitis?
measles
What are the inclusions called that you can see in SSPE?
Cowdry type A (eosinophilic cytoplasmic or nuclear)
What can you see on EM for SSPE?
Nucleocapsid filaments
What are the 3 ways measles can manifest in the CNS?
- Acute disseminated encephalomyelitis (postinfectious inflammatory)
- Subacute/chronic measles inclusion body encephalitis
- Subacute sclerosing panencephalitis
What are the 2 main diffs btwn Measles inclusion body encephalitis and SSPE?
- Inclusion body happens in months; SSPE is much more delayed (5-15 years)
- Inclusion body happens in immuno-impaired; SSPE happens in immunocompetent
What age group is more likely to develop SSPE if they get measles?
less than 18 mo
Which kills you faster: inclusion body encephalitis or SSPE?
Inclusion body encephalitis; usu fatal in a few weeks. Some people have SSPE for YEARS
which has more numerous identifiable inclusions: inclusion body encephalitis or SSPE?
inclusion body encephalitis
:)
Sometimes SSPE can have sparse ones but mostly absent if late in the game
4 clinical stages of SSPE
BMAC
1. Behavior changes
2. Myoclonus
3. Ataxia/spasticity
4. Coma/autonomic changes
(and then death)
Grossly affected areas in SSPE
Cerebral cortex
white matter
basal ganglia
thalamus
(so most of the brain lmao)
what neurodegenerative finding can you have in SSPE?
Tangles!
what is a potential (rare) complication of acute herpes encephalitis?
Chronic granulomatous herpes simplex encephalitis (which looks exactly like you think: granulomas + lymphs/plasma cells + calcs)
which virus has a delayed complication that involves atrophy of the cerebellum + fibrinoid necrosis + small BV mineralization?
Rubella
where in the brain do you find the most numerous PML lesions?
cerebral white matter
But they can also be in cortex and deep grey, less commonly cerebellum, brainstem/spinal cord
what causes PML?
JC virus
what is the time course for PML usually
“relentless progression” over a few months > increasing dementia > death
what can lead to remission of PML?
treatment of the underlying cause of the immunosuppression (so treating AIDS)
but watch out, cause it can cause inflammatory response and exacerbate PML
what can you see in the brain after “chasing the dragon”?
toxic leukoencephalopathy
4 histo findings of PML
- Bizarre astrocytes
- Multifocal demyelination w/ macs, very few lymphs
- JC virus inclusions
- Intranuclear polyomavirus particles (EM)
What IHC do you use for PML?
SV40
What type of cell are the JC virus inclusions found in?
Oligos (even though the astrocytes are the ones that get bizarre)
What causes HAM?
HTLV-1
(HTLV-1-associated myelopathy)
What’s the other name for HAM?
Tropical spastic paraparesis
(Think of ham with pineapple)
What part of the CNS does HAM/HTLV-1 affect?
Thoracic cord
What are the 3 possible gross findings in HAM?
- meningeal thickening
- atrophy of thoracic cord
- lateral fascicular column degeneration
What are the micro findings of HAM?
- mixed lymphs & macs, mostly in lower thoracic
- hyaline thickening of BVs
- degeneration of lateral tracts of cord
What does HIV look like on EM?
Virions have an envelope surrounding a cone-shaped core and very tiny “knobs” on their surfaces
what is the typical gross appearance of HIV/AIDS brain?
mild atrophy with modest ventriculomegaly +/- gray d/c of centrum semiovale
What are the 3 main histo findings of “subacute encephalitis of AIDS” or “HIV leukoencephalopathy”?
- microglial nodules + vacuoles (nonspecific)
- Leukoencephalopathy (duh) w/ patchy demyelination + gliosis
- multinucleated giant cells containing HIV antigen
what are the HIV antigens that you can identify in tissue with antibodies?
gp41
p24
where do the multinucleated giant cells of HIV tend to live?
near capillaries
what is the mechanism of CNS “neurotropism”?
- depends on chemokine receptor on cell surface
- some strains just like to cross the BBB
what is the difference in neuro deterioration between infants/children with HIV and adults?
infants/children: usu direct HIV infxn
adults: opportunistic infxn
where does vacuolar myopathy affect HIV patients?
spinal white matter: posterior columns and lateral corticospinal tracts, mostly thoracic
what entity does vacuolar myelopathy of AIDS mimic?
subacute combined degeneration of the spinal cord
what part of the brain shows abnormalities in HIV-assoc progressive encephalopathy of childhood?
Basal ganglia: severe atrophy and PERIVASCULAR calcs
Characteristic finding of Cryptococcus infxn (in HIV infxn)
Cribriform gross appearance d/t proliferation in Virchow-Robin spaces
(Crypto/cribriform)
Characteristic finding of Aspergillus fumigatus infxn (in HIV infxn)
hemorrhagic space-occupying lesions d/t angioinvasion (mycotic aneurysms are common)
Characteristic finding in coccidioides immitis (in HIV infxn)
microabscesses w/ large spherules with enclosed endospores inside giant cells + endarteritis obliterans
how can you tell CMV and VZV ventriculoencephalitis apart w/o IHC?
CMV will be super inflamed w/ partly necrotic ependymal and subependymal tissue
VZV will have inclusions but only slight rarefaction and minimal inflammation
what is neuro-IRIS?
neurologic immune reconstitution inflammatory syndrome
d/t CD8 cells going to town
What are the most common causes of mass lesions in the brain in a pt with HIV?
- TOXO
- Primary CNS lymphoma
- Fungus
- tuberculoma
- PML
- CMV
- something unrelated to HIV (like a glioma)
What are the 2 primary neoplastic complications of AIDS in the CNS?
- meningeal spread of a systemic lymphoma (common)
- primary CNS lymphoma (usu high-grade non-Hodgkin B-cell a/w EBV)
What is Rasmussen’s encephalitis?
Hemispheric inflammation > seizures
Rare, in kids, lateralized brain destruction & atrophy w/ chronic encephalitis
What are the 4 main micro findings of Rasmussen’s?
SNTS
1. Spongy cavitation (chronic)
2. Microglial Nodules near pyknotic neurons
3. Lymphocytic vessel cuffing with T-CELLS!
4. Sharp demarcation
(in setting of severe neuron loss & astrocytic gliosis; laminar astrocytic proliferation)
What is the clinical manifestation of Rasmussen’s encephalitis?
Seizures/epilepsy, usu onset btwn 2-17 yrs
epilepsia partialis continua (seizures lasting hours/days/years)