SUBCUTANEOUS MYCOSES Flashcards
(26 cards)
What are SUBCUTANEOUS MYCOSES?
A wide spectrum of diseases
Caused by heterogenous group of fungi
Typically involves dermis, subcutaneous tissue, fascia, bone, contiguous tissue
Nature of agents
Where are they found?
Means of nutrition?
What geographical location are they in?
most found in soil or on decaying organic matter,
most live as saprophytes
lesions gradually spread locally around the area of inoculation without dissemination to deep organs
Some have worldwide distribution while some are geographically restricted to the tropics
Routes of Infection
Direct subcutaneous inoculation
Traumatic implantation
Iatrogenic e.g. contaminated dressings
Pathogenesis of subcutaneous mycoses Q
- Initial lesions at or near the sites of inoculation, but eventually typically extends out into the epidermis
- the lesions become granulomatous and expand slowly from the area of implantation
- infection may remain localized or spread by direct extension through tissue or by lymphatics or hematogenous
- Rarely they become systemic and produce life-threatening disease
- Pathology is from fungal invasiveness and from host responses
- In many cases, the mycoses are difficult to treat and surgical intervention (e.g., excision or amputation) may be necessary
Types by Subcutaneous Mycoses
Sporotrichosis
Chromomycosis
Phaeohyphomycosis
Mycetoma
Discuss Sporotrichosis Q
Agent: Sporothrix schenckii
A thermally dimorphic fungus ?????
found in association with decaying vegetation and various plants such as sphagnum moss and rose bushes
Landscapers, gardeners and tree farmers
chronic infection
Rarely, pulmonary and disseminated forms of infection can occur when S. schenckii conidia are inhaled
Most infections occur in otherwise healthy individuals
disseminated cases were observed in AIDS patients
Sporothrix brasiliensis, however, is particularly transmitted from bites or scratches from stray cats which are considered a primary host of this fungus
Non-lymphangitic
Clinical manifestations: Discuss Lymphocutaneous Sporotrichosis
Most common manifestation
Follows traumatic implantation of the fungus (e.g. gardner’s disease)
Initial lesion is a small, hard, painless nodule, which becomes fixed over time and enlarges to form a fluctuant mass that eventually ulcerates.
Other nodules may develop and progress along the lymphatics draining the initial site, but infection rarely extends beyond the regional lymphatics.
Clinical manifestations: Fixed Cutaneous Sporotrichosis
Primary lesions develop at the site of implantation of the fungus, usually the hands and fingers
Lesions often start out as a painless nodule which ulcerates and discharges a serous or purulent fluid
remain localised around the initial site of implantation and do not spread along the lymphatic channels
where there is a high level of exposure and immunity in the population
Other types of sporotrichosis
Osteoarticular sporotrichosis
Sporothrix meningitis – Rare
Mucocutaneous
Extracutaneous disseminated sporotrichosis particularly in AIDS patients
Rarely, primary pulmonary sporotrichosis results from inhalation of the conidia
Simulates PTB
In px with cell-mediated immunity
Laboratory Diagnosis of Sporotrichosis
A tissue biopsy is the best specimen. Exudate may also be collected
Direct microscopy with KOH/calcofluor white stain
Culture: Growth is obtained after a few days white, pasty colonies of the yeast form at 37°C and branching mycelia (molds) at 25°C
Histology:
Gomori methenamine silver/PAS/fluorescent antibody staining
“asteroid bodies”
Serology??
What is the Treatment of Sporotrichosis?
Lymphocutaneous sporotrichosis
Itraconazole is the drug of choice
Saturated solution of potassium iodide in Milk, Terbinafine
continued for 2–4 weeks after all lesions have resolved (treatment lasts 3-6 months)
Extracutanerous sporotrichosis (osteoarticular sporotrichosis etc)
Often difficult to treat
Itraconazole
for at least 1 year.
Disseminated sporotrichosis, including CNS
treated initially with liposomal amphotericin B
followed by itraconazole after improvement has been noted.
Lifelong suppressive therapy with itraconazole is required for AIDS patients
Discuss Chromoblastomycosis Q
A chronic, localized subcutaneous infection also known as chromoblastomycosis (chromomycosis)
Characterised by verrucous (wart-like) lesions, which occur predominantly on the lower limbs
Traumatic inoculation with fungal agents in soil and vegetation
More in tropics
Aetiology of Chromoblastomycosis
Several species of dematiaceous (black pigmented) fungi
Fonsecaea pedrosoi
Phialophora verrucosa
Cladophialophora (Cladosporium) carrionii
What is the Pathogenesis of Chromoblastomycosis?
Infections are caused by the traumatic implantation of these fungal elements into the skin ; the lower limbs
Chronic, slowly progressive granulomatous lesions
Tissue proliferation usually occurs around the area of inoculation producing crusted, verrucous, wart-like lesions with extension along the draining lymphatics
Clinical features of Chromoblastomycosis
Clinical features
Starts as an itchy papule which is followed weeks to months later by formation of warty nodules or firm tumors
Small ulcerations or “black dots” of hemopurulent material are present on the warty surface
Long-term consequences include
Bacterial super-infection
Rarely, chronic lymphoedema/elephantiasis
Dissemination rarely
What is the Laboratory diagnosis of Chromoblastomycosis?
Specimen: Pus, Skin scrapings and/or biopsy.
Microscopic examination of crusts in KOH shows the presence of sclerotic bodies; irregular, 10-20 µm large, brown-walled elements with transverse septa
Culture: organisms grow as dark colored molds which can be identified by microscopic appearance of their hyphae and conidia on SDA
What is the Treatment of Chromoblastomycosis?
Surgical excision-small lesions
Cryotherapy
Local heat therapy
Antifungal agents e.g. itraconazole, terbinafine/flucytosine-large lesions
Chromoblastomycosis is not communicable
Wearing shoes and protecting the legs probably would prevent infection
Discuss PHAEOHYPHOMYCOSIS Q
term applied to infections characterized by the presence of darkly pigmented septate hyphae in tissue
usually subcutaneous but can also be systemic or involving the central nervous system
Solitary encapsulated cysts in the subcutaneous tissue to sinusitis to brain abscesses
Over 100 species of dematiaceous molds
Species of PHAEOHYPHOMYCOSIS
Exophiala jeanselmei
E. dermatitidis
E. spinifera
Cladophialophora bantiana
Curvularia spp.
Alternaria spp.
Traumatic implantation also implicated
Steam baths/ dishwashers
Decaying plants
Melanized hyphae
Specimens are cultured on routine fungal media to identify the etiologic agent
itraconazole or flucytosine is the drug of choice for subcutaneous phaeohyphomycosis
Amphotericin B and surgery for brain abscess
What are Mycetomas?
Mycetomas are chronic, inflammatory swellings with numerous draining sinuses
Triad of a painless subcutaneous mass, sinuses, and discharge containing grains (masses of fungal organisms)
The causative agent can be seen in the bloody or non-bloody pus, sometimes with the naked eye, in the form of granules
In 75% of cases, a mycetoma is localised on the foot (Madura foot)
In addition to involvement of soft tissue, extension to the bone can occur
Two pathogens
fungal moulds (cause eumycetomas)
filamentous bacteria in the order Actinomycetales. (cause actinomycetomas)
What is a Eumycetoma?
All causative agents of fungal mycetoma are exosaprophytes that have penetrated deep into the tissue with a splinter of wood or a thorn
Agents of eumycetoma include
Madurella mycetomatis
Madurella grisea (now Trematosphaeria grisea)
Pseudallescheria boydii
Exophiala jeanselmei
Bacterial causes of mycetoma include the following
Actinomadura madurae
Actinomadura pelletieri
Actinomyces israelii
Streptomyces somaliensis
Nocardia brasiliensis
Nocardia farcinica
Nocardia asteroids
Clinical presentations of mycetomas
Typically affects young male farmers; field workers, farmers, and fishermen
Most commonly affects the foot (Madura foot)-Traumatic inoculation
back, shoulders, and buttocks. Rarely, other body sites can be involved such as scalp, eye, jaw, and oral cavity
Starts as a small painless nodule which progresses to a chronic, subcutaneous swelling with serous discharge from multiple sinus tracts
Colonies of the organisms are seen in the serous discharge as small grains or granules
Progression from nodule to draining sinus tracts can take weeks, months, and even years
What are the complications of mycetoma?
Fractures of infected bone
Osteomyelitis
Bacterial super-infection
Pain??
