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27 Cards in this Set
- Front
- Back
Describe presentation of dermatophyte infections
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slowly progressive eruptions of the skin & appendages
unsightly, not painful or life threatening. manifestations vary, depending on inflammatory response typically involve erythema, induration, itching, and scaling. |
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What are th characteristics of the common dermatophytes?
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Form septate hyphae, macroconidia, and microconidia
morphology of conidia are basis for seperation |
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What are the major species that cause dematophyte infections?
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Epidermophyton, Microsporum, and Trichophyton are major genera
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Describe transmission of dermatophytes? What is the port of entry?
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low virulence and requires prolonged contact for human2human otherwise from animal or soil
- Port of entry is typically throuh minor skin breaks |
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What does tinea mean in latin? How is it used in medicine?
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worm
it is used to describe skin infection in medicine |
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What type of tissues do dermatophytes spread to?
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pread from skin to other keratinized structures, such as hair and nails, or may invade them primarily
- The hair shaft can be invaded and broken by hyphae ----------------------------- Black piedra. Note invasion by Piedraia hortae both within (endothrix) and outside (exothrix) the hair shaft. Dermatophyte invasion would be similar |
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What is important immunological response to dermatophytes?
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Th1 mediated by T cells is important
- Phagocytes are able to use oxidative pathways to kill the fungi both intracellularly and extracellularly |
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When might dermatphyte infections become widespread
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immunocompormised host w/ poor Th1 response
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What are the names for the sites of dermatophyte infections? (7)
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tinea capitis (scalp; Figure 44–3A),
tinea pedis (feet, athlete's foot), tinea manuum (hands), tinea cruris (groin), tinea barbae (beard, hair), and tinea unguium (nail beds). not included in this list are called tinea corporis (body) ------------------------------- Tinea capitis. A. Ringworm of the scalp with superficial lesions and loss of hair. B. Close-up using an ultraviolet lamp (Wood's light) reveals fluorescing hair fragments. The culture grew Microsporum audouinii. |
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What are the steps in tinea capitis?
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Erythematous paupule surrounding follicle -> scaling of scalp -> discoloration -> fracture of follicle -> Spread to adjacent follicles in ring manner
- Symptoms rare beyond hair loss and itching |
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What are the favorable conditions for fungi?
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moist areas and skin folds. Tight clothing
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What is athletes foot?
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scaling and splitting of the skin between the toes, is commonly known as athlete's foot. Moisture and maceration of the skin provide the mode of entry.
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How do you diagnose dermatophytes? What is the goal>
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Take scrapings from periphery of lesion.
KOH mounts of skin scrapings and infected hairs demonstrate hyphae. Some will fluoresce under wood's lamp - The goal is to differentiate from bacterial and parasitic infections |
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Do we culture dermatophytes?
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Generally no, does not change clinical management.
If KOH mount is negative then culturing is required |
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How are dermatophyte infections treated?
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Generally topical is enough.
Nail bed or more extensive dermatophyses may require systemic treatment |
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What rxs are used in the topical treatment? the systemic treatment?
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Topical tolnaftate, allylamines, or azoles usually sufficient
- Systemic griseofulvin or azoles used in refractory cases |
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Describe the typical sporotrichosis infection
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Sporotrichosis. A. This infection began on the finger and has started to spread up the arm, leaving satellite lesions behind. If untreated, these lesions will evolve into ulcers. B. A more advanced case beginning with inoculation in the foot. |
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What are the subcutaneous fungal infection disease types? what about the etiologies?
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Sporotrichosis - singel etiology = sporothrix schenkii
Chromoblastomycosis - caused by multiple fungi Mycetoma - caused by multiple fungi |
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What about the fungi SPOROTHRIX SCHENCKII? Why melanin?
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Dimporphic, hyphae are thin and septated, conidia clusters at end of hyphae, synthesizes melanin
- Melanin resists oxidative killing |
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What is pathogenesis of sporotrichosis?
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Injection of conidia to subQ tissue (thorn) -> Painless papule -> grows and ulcerates -> drains in lymphatics -> jumping nodules along lymph drainage pathway
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What do conidia and yeast cells bind to in SubQ infections?
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Fungi bind to Extracellular proteins
fibronectin, laminin, colagen |
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What is definitive diagnosis for Sporotrichosis?
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Culture of infected pus/tissue and demonstration of typical conidia & dimorphism
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What is the treatment for Sporotrichosis?
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Itraconazole though more invasive pulmonary/systemic may require in addtion Amphoterocin B
- Azole - 14 demethylase inhibitor in ergosterol synthetic pathway Ampho - pore forming at Ergosterol site |
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Describe chromoblastomycosis?
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1. Disease occurs typically on the foot or leg. It appears as papules that develop into scaly, pigmented, wart-like structures, usually under the feet.
2. Occurs people walk barefoot in tropics 3. No lymph involvement 4. Slow & painless |
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How treat chromoblastomycosis? What are most common agents?
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Surgery and antifungal therapy.
Flucytosine & Itraconazole |
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What is mycetoma?
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Clnical term for infection of foot associated w/ trauma that inoculates wound. May also be caused by actinomyces/nocardia
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Describe clinical presentation of mycetoma? How about treatment
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A massive induration with draining sinuses
Once established, the treatment of mycetoma is difficult |