Flashcards in Module 5 Path Continued: Herpes: Rocky, Qfever Deck (51):
How does a patient contract cytomegalovirus (HHV-5)?
Via body fluids (transplacental, saliva, urine, breast milk, blood transfusions) and organ transplant or vertically transmitted
What types of patients are at risk of contracting HHV-5?
1) Patients taking steroids
2) HIV/AIDS (CD4 less than 50)
In a immunocompetent person with HHV-5 what kind of infection will patients get?
Mononucleosis (but usually with EBV)
What is the most common organ transplant that leads to CMV?
Kidney so you will get nephritis
What is the most commonly affected in AIDS patients with CMV?
Retinitis -> cotton wool appearance
--can also affect lungs (interstitial pneumonina), GI( esophagitis), gastritis and duodenitis and colitis
CMV has a tropism for what?
Polyclonal B cell activator
What is the best investigation for CMV?
PCR (its a virus)
What are the cytopathic effects of CMV?
Cytomegalo (enlarged cell and nucleus)
Formation of intranuclear basophilic inclusions (owls eyes)
Intracytoplasmic inclusions which are mostly basophilic but can be eosinophilic
Patients can get what symptom of CMV if it affects the lungs?
Dry cough (nothing to cough up)
What does HHV5 become latent in?
B cell lymphoma
What are the three M's of Herpes viruses?
1. Chromatin Margination (splitting apart of the chromatin to nucleus)
2. Multinucleated Giant Cells
3. Nuclear molding ( coming together of nuclei)
What is the pathogenesis for herpes Zoster?
Inhalation of respiratory droplets ---- chicken pox ---- varicella zoster dormant in DRG ---- activates when immunocompromised state (stress because cortisol suppresses the immune system)
If patient has shingles and you have never had chickenpox nor had the vaccine, are you at risk of contracting shingles?
The patient can actually give you the chickpox virus but not actual shingles.
(patient has to be in the vesicle stage though)
What is the presentation of a patient with Shingles?
Painful vesicles and these rupture and to become ulcers and never cross midline and stay in the dermatome of the DRG
What is a complication of shingles?
Even after healing you can get something called post herpetic neuralgia ----neuropathic pain syndrome after shingles lesions are gone
What is the best investigation of shingles? what is the first investigation?
Best: PCR (its a virus so always PCR)
First: Tzanck smear -- scrape the vesicle and stain with Giemsa to visualize Tzanck cells (mutlinucleated giant cells ) in syncytia formation
What are the intranuclear eosinophilic inclusions?
Cowdry Type A (only seen in Herpes Zoster)
At what dermatomes does Shingles appear?
T4 (nipple) to the T10 (Umbilicus)
Rabies is normally transmitted to humans from dogs and bat,however, in the US what is the most common way to become infected with rabies?
Bite of a Raccoon or a droppling from a bat into an open cut
What is the prognosis for a patient infected with rabies?
This is based on the site of the bite (distance from bite site to brain determines prognosis)
---so getting bite on the leg or toe is a much better prognosis then arm or face
--travels PNS to CNS retrograde axonal transport
What are the symptoms a patient will have that is infected with rabies?
Hydrophobia (afraid to drink because swallowing of anything induces painful contractions of pharyngeal muscles plus the actual virus lives inside salivary glands)
What is the most common cause of death in rabies??
What is the most accurate test for rabies?
Made on autopsy -- negri bodies: intracytoplasmic eosinophilic inclusions found in purkinje cells
--only virus where PCR is not best test
How does a patient with viral myocarditis present?
Most common symptom is asymptomatic
can be flu like (prodrome)
what is the best investigation for viral myocarditis?
PCR after endomyocardial biopsy (have to go through the endometrium in order to obtain the biopsy)
What are the complications of viral myocarditis?
arrhythmias (because purkinje fibers run through the myocardium)
Dilated cardiomyopathy (because the virus cause fibrosis)
The next few questions are going to be comparing and contrasting viral myocarditis and myocardial infarction. In terms of etiology, how are they different
Viral Myocarditis: Coxsackie B (can be A)
MI: Atherosclerotic plaque with superimposed thrombosis
In terms of pathogenesis how are viral myocarditis and MI different
Viral Myocarditis: No ischemia and combination of direct damage by virus and damage via immune response/lymphatic infiltration
MI: ischemia leads to hypoxia and infiltration of PMNs, macrophages, and sheets of necrosis
In terms of inflammation and necrosis how are viral myocarditis and MI different?
Viral Myocarditis: Inflammation leads to necrosis
MI: Necrosis leads to inflammation
In terms of specimen appearance how does myocarditis and MI differ?
Viral Myocarditis: Patchy necrosis
MI: Necrosis of region of myocardium supplied by that artery
How does one become infected with viral myocarditis?
Inhalation and respiratory droplets that get into your blood
Viral myocarditis results in damage by what cells?
Indirect damage by CD8 lymphocytes in response to the virus itself (so CD8 lymphocytes cause more damage then the actual virus itself)
---this response leads to inflammation and eventually necrosis
What is the etiology for Rocky Mountain Spotted Fever?
Rickettsia Rickettsii (obligate intracellular bacteria: hides in endothelial cells and smooth muscle of arterioles)
---atypical bacteria in that it needs a host to feed off of
What is the vector for Rocky Mountain Spotted Fever?
Transmitted by tick bites (Seen mainly in campers and hikers)
What regions is Rocky Mountain Spotted Fever found in?
Georgia, Oklahoma, Arkansas, Tennessee
How does a patient present with rocky mountain spotted fever/
Presents about 1 week after bite
Myalgia (pain in muscle)
Vasculitic rash -Petechiae (starts from wrists and ankles and moves upward to trunk and then moves back down to palms and soles of feet)
Petechiae is due to vasculitis (So when you have endothelial damage you get vasculitis and this leads to petechiae)
Referred to as a Centripetal rash
what kind of cells do you find in a histology of rocky mountain spotted fever?
No neutrophils (Atypical)
get lymphocytes and monocytes
What is the best investigation for rocky mountain spotted fever?
Skin biopsy with immunofluorescence staining (allows you to directly visual organisms)
What is the second best investigation for rocky mountain spotted fever?
Weil-Felix test (latex of agglutination) (positive)
What are the complications of rocky mountain spotted fever?
Endothelial damage ---- thrombus and therefore acute ischemia so you get gangrene (Skin) and necrotizing pneumonia which leads to lung abscess and in the brain you see red infarct all due to acute ischemia
SO SKIN, LUNG AND BRAIN
One of the differnentials for Rocky Mountain Spotted Fever is Epidemic Typhus, what bacteria causes this?
Rickettsia Prowazeki (atypical bacteria that loves endothelial cells)
How is Epidemic Typhus spread?
Spread by head and body lice
In epidemic typhus you will see rash as well due to the endothelial proliferation and subsequent vasculitis, thrombosis and hemorrhage. however how is this rash different then Rocky Mountain Spotted fever rash?
Centrifugal rash : starts at the trunk and spreads towards the extremities and then spares the hands and soles of feet
Epidemic Typhus has the same complications and investigations as Rocky Mountain spotted fever
So skin, lung and brain
Skin biopsy with immunofluorescent staining (most accurate) and then Positive Weil-felix test
Q fever is caused by what bacteria?
Coxiella Burnetti (obligate intracellular)
How is Q fever transmitted?
Droplet infection (Airborne) from sheep and cattle (so its not through a bite)
How is Q fever different from epidemic typhus and rocky mountain spotted fever?
No skin rash!!! (Because no bite)
and a negative Weil-Felix test
ring granuloma on liver biopsy (central fat that is surrounded by epithelial histocites which are activated by macrophages) --- seen in liver not lung and this is an incidental finding no actual liver symptoms
Q fever causes interstitial pneumonia, why?
Alveolar epithelial cells because you are inhaling
What symptoms does Q fever cause?
Dry cough ---due to interstitial pneumonia
What is the best investigation for Q fever?
Serology (antibody titers)