Pathology of Infectious Diseases Flashcards
General pattern of infectious response with the following findings:
- increased vascular permeability
- PMN infiltrates
- pus
- release of chemoattractants
Suppurative or purulent
General pattern of infectious response with lymphoplasmacytic infiltrates - lymphocytic (if viral) or plasmacytic (if in a case of syphilis)
Mononuclear
General pattern of infectious response with caseating or non-caseating granuloma formation
Granulomatous
General pattern of infectious response with the following findings:
- inclusion bodies
- multinucleated giant cells
- host cell proliferation (such as in the case of HPV infection)
- usual association with neoplasia
Cytopathic or cytoproliferative
General pattern of infectious response with the following findings:
- severe gangrenous tissue necrosis
- ulcers
- rapid progression
- toxin- or lysis-mediated destruction
- lack of inflammatory cell infiltrate
Tissue necrosis
General pattern of infectious response with the following findings:
- repetitive injury
- fibrosis
- loss of normal parenchyma
Chronic inflammation and scarring
General pattern of infectious response associated with the following:
- extra cellular Gram-positive cocci
- Gram-negative rods (pyogenic organisms)
Suppurative or purulent
General pattern of infectious response associated with the following:
- general chronic infections
- acute viral infectious
- acute intracellular bacterial infections
- parasitic infections
Mononuclear
General pattern of infectious response associated with the following:
- Mycobacterium tuberculosis
- fungal infections
- schistosome eggs
Granulomatous
General pattern of infectious response associated with generally all viral infections
Cytopathic or cytoproliferative
General pattern of infectious response associated with the following:
- clostridia
- diphtheria
- Entamoeba histolytica infections of the colon or liver
- HBV infection of the liver
- herpesvirus infection of the brain
Tissue necrosis
General pattern of infectious response associated with the following:
- HBV infection
- schistosome infection
Chronic inflammation and scarring
RNA or DNA virus?
Measles virus (MeV)
RNA
Common RNA viruses include: Measles virus,
Mumps virus
RNA or DNA virus?
Mumps virus (MuV)
RNA
Common RNA viruses include: Measles virus,
Mumps virus
RNA or DNA virus?
Herpes simplex virus (HSV)
DNA
Common DNA viruses include: HSV, VZV, CMV, EBV
RNA or DNA virus?
Varicella zoster virus (VZV)
DNA
Common DNA viruses include: HSV, VZV, CMV, EBV
RNA or DNA virus?
Cytomegalovirus (CMV)
DNA
Common DNA viruses include: HSV, VZV, CMV, EBV
RNA or DNA virus?
Epstein-Barr virus (EBV)
DNA
Common DNA viruses include: HSV, VZV, CMV, EBV
Morphology of this viral illness is described as follows:
- Warthin-Finkeldey cells
- Koplik spots (prodrome)
- blotchy, reddish-brown rash of the face, trunk, and proximal extremities
Measles
In measles, the multinucleated giant cell with eosinophilic intranuclear AND cytoplasmic inclusions
Warthin-Finkeldey cells
In measles, described as necrotic lesions with PMN infiltrates and neovascularization near the opening of the Stensen ducts
Koplik spots (seen at the prodrome phase of measles)
Morphology of this viral illness is described as follows:
- mononuclear infiltrates predominantly in parotid gland, testes, and brain
- parotitis: bilateral (70%) with necrotic debris and duct damage
- orchitis: swelling against tunica albuginea predisposing to infarction, atrophy, scar formation, and sterility
- pancreatitis: fat necrosis
- encephalitis: perivascular infiltrates (mononuclear cuffing) and perivenous demyelination
Mumps
Morphology of this viral illness is described as follows:
- multinucleated syncitia with large, pink-to-purple intranuclear inclusions (Cowdry type A bodies)
- several disease entities: gingivostomatitis, genital infection, temporal lobe encephalitis, epithelial keratitis, stromal keratitis, disseminated disease (esophagitis, hepatitis, Kaposi varicelliform eruption, bronchopneumonia, eczema herpeticum, etc.)
Herpes simplex virus (HSV)
HSV is the can be an infectious agent of:
- gingivostomatitis (HSV-1)
- genital herpes (HSV-2)
- temporal lobe encephalitis
- herpes epithelial keratitis & herpes stromal keratitis
- disseminated herpes disease (esophagitis, hepatitis, Kaposi varicelliform eruption, bronchopneumonia, eczema herpeticum, etc.)
These are the large, pink-to-purple intranuclear inclusion bodies found in the multinucleated syncition in a herpes simplex virus (HSV) infection
Cowdry type A bodies
Morphology of this viral illness is described as follows:
- centrifugal rash - intraepithelial vesicles, described as “dewdrops on a rose petal”
- inclusion bodies within epithelial cells of the vesicle base
- reactivation leads to shingles (herpes zoster)
Varicella zoster virus (VZV) or chickenpox
Classic pattern or distribution of the chickenpox or VZV rash
Centrifugal
Reactivation of this VZV leads to a viral illness described with the following morphology:
- dermatomal distribution of vesicular rash
- dorsal root ganglion cell necrosis, painful radiculoneuritis, with mononuclear cell infiltrates
- herpetic inclusion bodies within the dorsal root ganglion cell
Shingles or herpes zoster
Syndrome associated with VZV, like shingles, described to have herpetic inclusion bodies and mononuclear cell infiltrates, but additionally described to be with facial paralysis and hearing loss
Ramsay Hunt syndrome
Morphology of this viral illness is described as follows:
- large cells with atypia and intranuclear basophilic inclusions surrounded by a clear “halo” (owl’s eye inclusions)
- responsible for heterophile-negative or Monospot-negative mononucleosis
- associated with congenital infections (blueberry muffin baby)
Cytomegalovirus (CMV)
Most oral herpes or herpes gingivostomatitis cases are caused by this particular HSV type
HSV-1 (herpes simplex virus type 1)
Most genital herpes cases are caused by this particular HSV type
HSV-2 (herpes simplex virus type 2)
Morphology of this viral illness is described as follows:
- “transforming virus”, responsible for mononucleosis, nasopharyngeal carcinoma, and lymphomas (especially Burkitt lymphoma)
- atypical lymphocytes in peripheral blood and tissue (Downey cells)
- expanded paracortical areas by over-activated T cells, causing lympadenopathy (paracortical hyperplasia)
- responsible for hereophile-positive or Monospot-positive mononucleosis
- splenic rupture due to rapid splenomegaly producing increased tension over a fragile splenic capsule or the capsula fibrosa splenica
Epstein-Barr virus (EBV) infection
CMV infection’s unique inclusion bodies described as intranuclear basociphilic inclusions surrounded by a clear “halo”
Owl’s eye inclusions
Atypical lymphocytes found in the peripheral blood and tissue of an Epstein-Barr virus infection
Downey cells
Expression of heterophile (Monospot) antibodies in EBV infection
Positive
Expression of heterophile (Monospot antibodies in CMV infection
Negative
Gram-positive bacteria involved in pyogenic, suppurative infections with extensive tissue destruction, most commonly in the form of the following:
- skin and soft tissue infections: folliculitis, furuncles, carbuncles, cellulitis, hidradenitis suppurativa, mastitis, SSI, paronychia, and felons
- pneumonia: post-viral pneumonia and necrotizing pneumonia
- scaled skin syndrome (SSS) or Ritter disease
Staphylococcus aureus
Pneumonia caused by Staphylococcus aureus described to involve a greater degree of tissue destruction, further complicated by empyema, abscess, or a pneumatocoele
Staphylococcal necrotizing pneumonia
Syndrome where Staphylococcus aureas exfoliatin cleaves desmoglein in the desmosomes, separating the epidermis at the stratum granulosum
Scalded skin syndrome (SSS) or Ritter disease
Staphylococcus aureas exotoxin responsible for cleaving desmoglein in the desmosomes in SSS or Ritter disease, separating the epidermis at the stratum granulosum
Exfoliatin
Desmosome cadherin cleaved by the Staphylococcus aureus exotoxin exfoliatin in Ritter disease or SSS
Desmoglein
Area of skin separated in Ritter disease or SSS
Stratum granulosum in the epidermis
Spectrum of illness where drug reactions (or rarely, infection with Mycoplasma pneumoniae, Dengue virus, or cytomegalovirus) creates a CD8+ T cell-mediated destruction of keratinocytes, separating the skin at the dermo-epidermal junction (DEJ)
Toxic epidermal necrolysis (TEN) or Lyell disease or Stevens-Johnson syndrome (SJS)
Usual pathogenesis of skin separation in toxic epidermal necrolysis (TEN) or SJS destroying keratinocytes, ultimately separating the dermo-epidermal junction
CD8+ T-cell mediated reaction initiated by drug reaction
TEN/SJS is commonly caused by the following: (mnemonic PCP LAPSE) - phenytoin - carbamazepine - phenobarbital - lamotrigine - allopurinol - penicillin - sulfa drugs - erythromycin
< 20% is caused by M. pneumoniae, DENV, CMV infections; HIV/AIDS and SLE known to increase the risk
Area of skin separated in Lyell disease or TEN
Dermo-epidermal junction (DEJ)
The more severe form of the TEN/SJS spectrum
Toxic epidermal necrolysis (TEN) or Lyell syndrome
The less severe form of the TEN/SJS spectrum
Stevens-Johnson syndrome (SJS)
8 common TEN/SJS-causing drugs
Mnemonic: PCP LAPSE
- phenytoin
- carbamazepine
- phenobarbital
- lamotrigine
- allopurinol
- penicillin
- sulfa drugs
- erythromycin
2 disease states known to increase the risk of TEN/SJS
HIV/AIDS & SLE
Gram-positive bacteria involved in pyogenic, suppurative infections with mild tissue destruction, classically associated with the following:
- erysipelas
- pharyngitis
- scarlet fever
Streptococcus pyogenes (group A streptococcus)
Group A streptococcal (Streptococcus pyogenes) diffuse, edematous, neutrophilic, PAINFUL inflammatory reaction of the dermis and epidermis, usually extending into the subcutaneous tissue; with well-demarcating serpiginous borders
Erysipelas
Group A streptococcal (Streptococcus pyogenes) edematous inflammation of the pharynx, presenting with the following:
- epiglottic swelling
- punctate tonsillar crypt abscesses
- cervical lymphadenopathy
Streptococcal pharyngitis or GAS pharyngitis or “strep throat”
Group A streptococcal (Streptococcus pyogenes) post-pharyngitic pyogenic illness presenting with fever, strawberry tongue, centrifugal sandpaper rash, Pastia’s lines, and desquamation
Scarlet fever
Toxin seen in lysogenized strains of GAS responsible for scarlet fever
Erythrogenic toxin
Susceptibility test for scarlet fever
Dick test
Gram-positive bacteria involved in suppurative infections, classically associated with the following:
- pseudomembranes
- airway obstruction
- marked vascular congestion
- interstitial edema
- myocarditis due to fatty change with isolated myofiber necrosis
- polyneuritis due to degeneration of myelin sheaths and axis cylinders
Corynebacterium diphtheriae
Corynebacterium diphtheriae toxin (diptheria toxin) can cause necrosis of the epithelium, followed by an outpouring of dense, fibrinosuppurative exudate, forming this thick layer of debris resembling a membrane
Pseudomembrane
Gram-positive bacteria involved in suppurative infections classically associated with the following:
- the typical cause of bacterial meningitis
- creation of focal abscesses that are grayish-to-yellow in color and nodular in shape, representing necrotic amorphous basophilic tissue debris
- intrcellular Gram-positive bacilli in CSF
- etiologic agent of granulomatosis infantiseptica
Listeria monocytogenes
Gram-positive bacteria involved suppurative infections of BOTH neutrophilic and macrophagic infiltrates, associated with the following:
- tissue necrosis and exudative inflammation
- mediastinal hemorrhagic lesions (vasculitis, enlarged hilar and peribronchial lymph nodes)
- large, boxcar-shaped extracellular bacteria in chains
- spread cutaneously, inhalationally, or via ingestion
Bacillus anthracis
Gram-positive bacteria involved suppurative infections, particularly with central liquefaction that does NOT form granulomas, further described as:
- slender, beaded, Gram-positive bacteria with branching filaments
- seen best in a modified acid-fast stain called Fite-Faraco stain
Nocardia asteroides
This modified acid-fast stain is used to better visualize acid-fast staining bacilli and bacteria with branching filaments such as Nocardia asteroides
Fite-Faraco modified acid-fast stain
Gram-negative bacteria involved in suppurative infections, associated with the following:
- hemorrhagic lesions eventually leading up to DIC
- Gram-negative intracellular diplococci
- etiologic agent in meningococcemia
Neisseria spp. (N. gonorrhoeae and N. meningitides)
Gram-negative bacteria involved in suppurative infections, associated with the following:
- laryngotracheobronchitis (pertussis or whooping cough)
- bronchial mucosal erosion and hyperemia
- copious mucopurulent exudate
- haze of bacilli entangles with bronchial epithelial cilia
Bordatella pertussis
The laryngotracheobronchitis known as whooping cough
Pertussis (agent: Bordatella pertussis, a Gram-negative bacillus)
The layngotracheobronchitis known as barking cough
Croup (agent: Parainfluenza virus - 75%)
(Other viral agents:
- Influenza virus types A and B
- Measles virus
- Adenovirus
- Respiratory syncytial virus (RSV)
Other bacterial agents:
- Corynebacterium diphtheriae in laryngeal diphtheria
- Post-viral secondary bacterial growth of Staphylococcus aureus, Streptococcus pneumoniae, Hemophilus influenzae, and Moraxella catarrhalis in bacterial tracheitis, laryngotracheobronchitis, and laryngotracheobronchopneumonitis
Spasmodic croup: same etiology and pathophysiology, but lacking the usual signs of fever, inflammation, etc.)
Gram-negative bacteria involved in suppurative infections, associated with the following:
- etiology of necrotizing pneumonia with fleur-de-lis pattern of necrosis: necrotic centers with red, hemorrhagic peripheries
- etiology of ecthyma gangrenosum
- etiology of Gram-negative bacterial vasculitis: masses of pseudomonads forming a pervascular blue haze
Pseudomonas aeruginosa
Pseudomonal pneumonia with fleur-de-lis pattern of necrosis, described as necrotic centers with hemorrhagic peripheries
Pseudomonal necrotizing pneumonia
Pattern of necrosis seen in the necrotizing pneumonia caused by Pseudomonas aeruginosa, described as necrotic centers with hemorrhagic/red peripheries
Fleur-de-lis pattern
Pseudomonal (Pseudomonas aeruginosa) infection of the skin, causing well-demarcated necrotic and hemorrhagic oval lesions
Ecthyma gangrenosum
Gram-negative bacteria involved in massive proliferating infections with the following histologic features:
- early appearance of protein and polysaccharide-rich effusions
- few cells
- tissue AND vascular necrosis
- PMN infiltrate at the sites of healing (healing margins)
Yersinia pestis
Yersinia pestis infection associated with lymph node enlargement or buboes
Bubonic plague
Yersinia pestis infection associated with severe, confluent, necrotizing AND hemorrhagic bronchopneumonia
Pneumonic plague
Yersinia pestis infection associated with mononucluear phagocytes, developing foci of necrosis, leading to a more diffuse disease presentation
Septicemic plague
Gram-negative, usually genital, infection involved in the following:
- painful genital ulcers with shaggy, irregular, non-indurated borders (chancroid)
- yellowish-gray exudate
- layered: superficial zone of neutrophilic debris and fibrin, underlying zone of granulation tissue of necrotis and thrombosed vessels, and a dense lymphoplasmacytic infiltrate with Gram-negative coccobacilli beneath the granulation tissue
- lymph node buboes eventually eroding into sinuses
Haemophilus ducreyi (chancroid or soft chancre)
Gram-negative, usually genital, infection involved in the following:
- beefy-red genital ulcer with indurated borders (due to marked epithelial hyperplasia at the borders or pseudoepitheliomatous hyperplasia)
- associated with scarring and strictures
- seen as minute, encapsulated coccobacilli in macrophages on Giemsa/Warthin-Starry stain (Donovan bodies)
Klebsiella granulomatis
The soft, painful, irregular/shaggy-bordered genital ulcer of Haemophilus ducreyi infections
Chancroid or soft chancre
Appearance of Klebsiella granulomatis on Giemsa or Warthin-Starry stain as encapsulated coccobacilli in macrophages
Donovan bodies
Specific stain used to visualize Klebsiella granulomatis as “Donovan bodies” encapsulated in macrophages
Giemsa stain or Warthin-Starry stain
Acid-fast staining bacteria involved in tuberculosis, characterized with the following:
- granuloma-forming, surrounded by epithelioid (activated macrophages) and multinucleated giant cells (Langhans type cells)
- caseation necrosis
- relies on an intact cell-mediated immunity: chronic, granulomatous
Mycobacterium tuberculosis
In the setting of tuberculosis, this cytokine is released by antigen-presenting cells (APCs) to mediate T cell differentiation into helper T cells type 1 (TH1 cells)
Interleukin-12 (IL-12)
In the setting of tuberculosis, this cytokine is released by helper T cells type 1 (TH1 cells) to mediate the activation of macrophages, enabling them to be bacteriocidal against Mycobacterium tuberculosis and further serve purpose as an epithelioid cell in granuloma formation
Interferon-gamma (IFN-g)
In the setting of tuberculosis, IL-12 is released by these types of cells to mediate T cell differentiation into helper T cells type 1 (TH1 cells)
Antigen-presenting cells (APCs)
In the setting of tuberculosis, IFN-gamma is released by these cells to mediate the activation of macrophages, enabling them to be bacteriocidal against Mycobacterium tuberculosis and further serve purpose as an epithelioid cell in granuloma formation
Helper T cells type 1 (TH1 cells)
Product of granulomatous response in tuberculosis, made up of epithelioid cells (activated macrophages) and multinucleated giant cells (Langhans type cells)
Granuloma