Superficial cutaneous and subcutaneous fungal infections Flashcards
Superficial mycoses
agents of superficial mycoses are fungi that colonize the keratinized outer layers of the skin, hair, and nails. infections caused by these organisms elicit little or no host immune response and are nondestructive and thus asymptomatic. They are usually of cosmetic concern only and are easy to diagnose and treat.
Pityriasis versicolor
Asymptomiatic colonization of the stratum corneum. Pityriasis versicolor is a disease of healthy persons that occurs worldwide, but it is most prevalent in tropical and subtropical regions. Young adults are most commonly affected. Pityriasis versicolor has not been documented in animals. Human infection is thought to result from the direct or indirect transfer of infected keratinous material from one person to another.
Pityriasis versicolor Etiological agent:
malassezia furfur
Pityriasis versicolor Unique risk factor
condition that reduces the rate of desquamation, that is shedding of epidermal cells, predisposing factors; poor nutrition, excessive sweating and pregnant
Pityriasis versicolor General characteristics, tissue affected and clinical features
General characteristics: a lipophilic, yeast like organisms. It is part of normal flora, found in areas of body rich in sebaceous glands
tissue: Skin
clinical features: hyper pigmented or hypopigmented macular lesions that scale readily, giving it chalkybranny appearance, that occurs most frequently on the upper torso, arms and abdomen.
M. Furfur description
Dimorphic. Lipophilic, opportunistic, interfere with melanin production. Transient, superficial and scaly. Also associated with seborrheic dermatitis and dandruff.
upper trunk, arms, chest, shoulders, face and neck are most often involved, but any part can be affected.
Irregular, well demarcated patches of discoloration that may be raised and covered in fine scale.
NO host reaction occurs and the lesions are symptomatic with the exception of mild pruritus in severe cases.
Diagnosis: pityriasis veresicolor
Diagnositc procedures: although not usually necessary for establishing the diagnosis, culture may be performed using synthetic mycologic media supplemented with olive oil. Microscopically, the colonies are compirsed of budding yeast like cells with occasional hyphae.
KOH treated
Woods lamp: pale yellow
Pityriasis versicolor treatment
Preparation containing selneium disulfide, hyposulfite, thiosulfate or salicyclic acid, ketoconaozle.
Tinea nigra: appearance
appears as a solitary, irregular, pigmented (brown to black) macule, usually on the palms or soles. There is no scaling or invasion of hair follicles, and the infection is not contagious.
Tinea nigra: Considerations
Because of its superficial location, there is a little or no discomfort or host reaction. Because the lesion grossly may resemble a malignant melanoma, biopsy or local excision may be considered. Such invasive procedures may be avoided by a simple microscopic examination of skin scrapings of the affected area.
Tinea nigra: laboratory diagnosis and tx
10 to 20% KOH treated
scraping yeast like cells with hyphal fragments
TX: with azole cream
Cutaneous mycosis
involves diseases of the skin, ahir and nails. Generally affected keratnized layers of the itegument and its appendages. They can use keratin as nitrogen source. The organisms which participate in these infections are known as dermatophyte.
tinea faciei
ringworm of the face
tinea capitis
ringoworm head
highly contagious
hair becomes grayish, dull and brittle due to exctothrix invasion of hair, hair breaks off near the base of the shafts
more common in prepubescent children
t tonsurans is the principal agent of tinea capitiss in the united states
tinea corpris
ringworm of body
tinea manus
ringworm of hand
contact with another site of infection, particularly the feet or groin
direct contact with an infected animal or soil
tinea pidea
ringworm of feet
tidea unguium (oncherchyosis)
ringoworm of nails
candida: irregular boarder between the pink portion of the nail and the white outside edge of the nail when the nial has lifted from the nail bed. Larger portion of the nail is opaque, can be whitened or discolored to yellow or green. Discoloration underneath the nail may occur as a result of secondary infection.
tinea cruris
ringworm of groin
anthropophilic
associated with humans
zoophilic
associated with animals
geophilic
found in the soil
microsporum
keratin of skin and hair
fusiform or spindle shape conidia
epidermophyton
keratin of skin and nails
snow shoe or beaver’s tail macroconidia with thin smooth walls
trichophyton
keratin of hair, skin, and nail
penic or cigar shaped microcondia more in number than macoconidia
immunity of cutaneous mycosis
no classical humoral or cell mediated protective immunity
allergic reaction leads to lesions at different sites from the infection. these lesions are called dermatophytids or ids.
diagnositcs features of cutaneous mycosis
KOH of hair or scalp scrapings
growth on speacialized media
wood’s lamp
tx of cutaneous mycosis
local: azole
systemic: griseofulvin
tidea unguium trichophyton rubrum
trichophyton rubrum most common etiological agent. Fluorescence yellow to green under wood’s lamp
finger nail infections cured more quickly than toenail infections.
tinea ungium candida
candida: irregular boarder between the pink portion of the nail and the white outside edge of the nail when the nial has lifted from the nail bed. Larger portion of the nail is opaque, can be whitened or discolored to yellow or green. Discoloration underneath the nail may occur as a result of secondary infection.
laboratory diagnosis of cutaneous mycosis and tx
KOH of the hair or scalp scrapings
growth on specialized media. Characteried by a specfic pattern of growth in culture and by production of macro conidia and micro conidia
miconazole, clotrimazole and econazole.
oral: griseofulfivn, itraconazole, fluconazole, and terbinafine.
Woods lamp
light that uses long wave ultraviolet light. When an area of scalp that is infected with tinea (a type of ringworm fungus) is viewed under a wood’s light the fungus may glow. this test may be done to detect the presence of a fungal scalp or skin infection.
Subcutaneous mycoses common features
fungal infections that are implanted by trauma. The infections initially involve the deeper layers of the dermis, subcutaneous tissue or bone.
they are associated with some form of trauma occurring at the site of infection before the lesions developed
the infections occur on parts of the body that are most prone to be traumatized
the etiological agents are usually organisms commonly found in the soil or on decaying vegetation
they all produce granuloma
Sporotrichosis: gross and the five types of infection
chronic infection charactereized by nodular lesions of the cutaneous or subcutaneous tissues and adjacent lymphatics that suppurate, ulcerate, and drain. Sporothrichosis can be separated into five types of infection, lymphocutaneous, fixed cutannous, mucocutaenous, disseminated, and pulmonary.
Lymphocutaenolus sporotrichosis Etioogy
Etiology: Sporothrix schenckii. Dimorphic (mold to yeast). Common in the USA. Fungus that aaffets the skin and lymphatic system.
Lymphocutaenolus sporotrichosis: clinical features
nodular and ulcerative lesions that develop along lymphatics that drain the primary site of incoulation. Despite involvement of the lymph channel, is localized without fever or malaise and without involvement of the regional lymph nodes. those in the axilla or groin.
Fixed cutanneous lesions
Fungus remains limited to the skin and does not involve the lymphatics
Diagnosis of Sporothrix schenckii
Culture, skin tissue specimen presevered in 10% KOH show cigar shaped budding yeast form of S. Schenckii.
Asteroid bodies may be present. Star shaped with rays of an eosinophjillic material radiating from central yeast like cell or cells. The yeast like cell is basophilic, 3-5 um in diamter. The entire complex may be 10 to 15 um in diameter.
TX of Sporothrix schenckii
potassium iodid (oral in milk) (cutaneous infection
amphotericin B (disseminated infection)
Chromoblastomycosis etiology
dematiaceous (pigmented) fungi (phialophora and cladosporium). The most common agent is Fonsecaeea pedrosi. most common in tropical and subtropical regions.
Chromoblastomycosis clinical features
see in workers injured with woods
characterized by the development of papules at the site of incoulation which over the years become verrucous (warty) crusted. At the progression of the lesion: appears to vegetate, “cauliflower like” appearance, it is characterized by the development of Verrucous (warty) nodules at the site of inoculation.
Chromoblastomycosis DIagnosis and treatment
presence of pigmented fungi in tissue sections or pus. The thick walled cells are called sclerotic bodies or medlar bodies (copper colored spherical yeast). Culture
Surgical excision in the early stages. 5FU.
Phaeohyphomycosis (subcutaneous fungal infection) description
Darkly pigmented fungal elements. Cerebral or subcutaneous infection. These fugni can also cause chronic paransal sinusitis, prosthetic valve endocarditis, keratomycosis and widely disseminated infections
Phaeohyphomycosis Causative agents
numerous and varied. Dematiaceous hyphomycetes and most common and they rpoduce melanin in the cell wall
Phaeohyphomycosis Diagnosis and tx
DX: periodic acid schiff or methenamine silver stain: dark walled hyphae
TX: surgical resection of well localized lesions. Amphotericin B, oral ketoconazole and itraconazole
Fungal mycetoma clinical
tumefaction, draining sinuses and sclerotia (granules, grains). Maduromycosis, madura foot defroming infection on the foot or the hand may take years to develop. The infections start as small indurated subcutaneous papules. The tissue exudates white, yellow or black granules.
Fungal mycetoma: etiology and SX
petriellidium boydii is the most common eumycotic mycetoma in the united states and europe.
SX: massive induration with draining sinuses
Fungal mycetoma: DX and TX
DX: macroscopically examination fo sclerotia. Sclerotia are mounted in sterile salin and then crushed microscopically fungal hyphae with many intercalary swollen cell can be seen.
TX: difficult to treat with antimycotic drugs. Amputation is usually the final action.
