Fungi - Clinical Case studies: Skin and soft tissue infections Flashcards
What we should understand:
Focus on common presentations in clinical settings:
Is it fungal?
Pitfalls
Commonly encountered fungal infections in clinical settings:
Identification
Diagnosis (clinical, microbiological)
How does fungal infections most commonly present?
As opportunistic infections (Cutaneous infections, abdominal infection, lung infection, systemic infection)
How are fungal infections acquired?
From soil, tap water, mouldy kitchen/bathroom
Human-to-human transmission is rare with the exception of tinea (ringworm)
How are clinical presentations of fungal infections classified?
Superficial and cutaneous mycoses
Subcutaneous mycoses
Opportunistic mycoses
Deep seated mycoses
What are superficial mycoses? What are cutaneous mycoses?
Limited to outer layer of skin and hairshaft. The cutaneous mycoses also include deeper layers such as the epidermis. Thus they include invasive hair and nail infections.
What are subcutaneous mycoses?
Involve the dermis, subcutaneous tissues, muscles and fascia
What fungi are commonly involved in subcutaneous mycoses?
Dematiaceous hyphomycoses
Some diamorphic fungi (sporothrix and candida)
What are deep seated mycoses?
Systemic infections in hosts who are not necessarily immunosuppressed.
What fungi cause deep seated mycoses?
Mostly caused by dimorphic fungi with the exception of cryptococcus neoformans. (most commonly coccidioides immitis and paracoccidioides brasiliensis)
Which fungi are capable of causing opportunistic infections?
Most fungi can but the most common causes are:
Mucormycosis
Hyalohyphomycosis
Phaeohyphomycosis
How can a rash be differentiated?
Onset (abrupt, gradual spreading, recurrent)
Character (macular, papular, vesicular)
Site and Distribution (Localised, patchy, generalised, mucosal involvement, photosensitive or dermatomal)
Associated symptoms (viral prodromal)
Associated risk factors
What does macular mean?
Consisting of a distinct spot or spots.
What does papular mean?
Composed of elevated bumps
What does vesicular mean?
Blistering rash
What else can a localized rash be? (Differential diagnosis)
Contact dermatitis with or without bacterial colonisations
Psoriasis
Radiation dermatitis
Fixed drug reactions
Infective cause
Systemic reaction (Autoimmune)
What rashes are important to recognize because they are life threatening?
Steven-Johnson syndrome
Drug Rash with Eosinophilia and Systemic Syndrome (DRESS)
Meningococcal bacteraemia
Pemphigus vulgaris
What is Steven-Johnson syndrome?
A severe allergic reaction to medications affecting skin and mucus membrane.
What drugs cause Steven-Johnson syndrome?
Sulphonamides
Allopurinol
NSAIDs
What does meningococcal rash look like?
Petechiae rash caused by peripheral thrombosis/necrosis of tissues.
What is pemphigus vulgaris?
Severe autoimmune disease where blisters develop on skin and mucus membranes
What investigations must be conducted for an undiagnosed rash?
Guided by history and clinical examinations.
Blood tests include Full blood picture (WBCs and Eosinophil counts), C-reactive protein, and liver function tests.
Histopathological and microbiological testings (H&E stain, immunofluorescence stain for autoimmune disease. microscopy, culture, molecular tests, and serology)
If histology and culture can give definitive diagnosis why is it important to have an idea of what the diagnosis of a condition might be?
In order to allow treatment to be initiated asap.
What is candida?
A yeast (unicellular fungi)
How do candida reproduce?
Budding
Where is candida commonly found?
Animals, soil, hospital
Also normal commensals of humans (found on skin, GI tract, and vagina)
Why is species identification important for candida?
Different species are treated in different ways
How does candida cause disease?
Coloniser of gut under normal circumstances (pathogenic in immunocompromised)
What could cause candida albicans infection in someone who isn’t immunocompromised?
It can be caused by Iatrogenic factors such as antibiotic use, indwelling catheters and prosthesis.
What kind of disease is most commonly produced by candida?
Skin and mucous membrane infections. invasive disease is possible but uncommon.
What is intertrigo?
An inflammatory condition of skin folds, induced or aggravated by heat, moisture, maceration, friction, and lack of air circulation
What are the types of candidiasis?
Intertrigo
Localised folliculitis, balanitis
Candida diaper rash
Paronychia (nail infection)
What are the types of mucous membrane infections caused by candida?
Thrush
Candida esophagitis
Vulvovaginitis
What invasive diseases can be caused by candida?
Bacteraemia
Endocarditis
Enophthalmitis
Urinary tract candidiasis
What does thrush look like?
Whitish yellow center surrounded by reddening of the mucous membrane
Diagnosis of candida infections:
Mostly made from clinical exam
Lab testings (samples from intact pustules, skin biopsy tissue or desquamated skin can help support diagnosis)
Swab is inaccurate
Microscopy and culture as well as histopathology
How is candidiasis managed?
For most cutaneous disease investigations for underlying predisposing factors are conducted (diabetes, oral antibiotics, treat dermatoses, clean and dry skins appropriately)
Medication (includes topical antifungal which is usually sufficient, oral is used if it isn’t)
What medication is used for treatment of candidiasis?
Cotrimazole 1% cream B.D for 2 weeks, nystatin 100000 u/g cream BD for 2 weeks
How does dermatophyte infection present?
Annular lesion (ring-like) with dry scaly skin in the center and slightly raised with inflamed spreading margin.
It can also present as an erythematous rash or plague like.
Hyperkeratotic eruption can also be seen.
Commonly associated with pruritis.
What are the 3 important genera of dermatophytes?
Trichophytan
Microsporum
Epidermophyton
What are the modes of transmission of dermatophyte infections?
Anthopophiliac (human to human)
Zoophilic (animal to human)
Geophilic (environment to human)
What do dermatophytes require for growth?
Keratin
What is the infection by dermatophytes called?
Tinea
What are the types of tinea?
Tinea capitis (scalp)
Tinea corporis (body)
Tinea unguium (nails) [oncychomycosis]
Tinea cruris, barabe, pedis, etc
What is onychomycosis?
Dystrophic nail (only 50% have a fungal aetiology)
What is pruritis?
severe itching of the skin, as a symptom of various ailments
What is hyperkeratosis?
Abnormal thickening of the outer layer of the skin
How is tinea diagnosed?
Skin+nail scrapings and epilated hairs (nail scrapings can be falsely negative in 30% of cases)
Microscopy (fungal hyphae and/or arthroconidia
Culture (more reliable and permits species of fungus involved to be accurately identified.
How is tinea treated?
Depends on location and organism involved. Topical therapy is only used in tinea corporis, pedis, and cruris.
Tinea capitis and onychomycosis require systemic therapy.
[topical treatment less effective than systemic therapy]
What drugs are used to treat tinea?
terbinafine (first line since its more effective)
griseofulvin (microsporum canis is less susceptible to terbinafine so griseofulvin is used instead)
What is another name for sporotrichosis? Why?
Rose handler disease. It is caused by inoculation injury from soil.
Where is sporotrichosis commonly seen?
Certain parts of Australia (Margaret River regions)
How does infection take place in sprotrichosis?
Mainly a localising disease which may or may not spread to lymph nodes.
How is sporotrichosis diagnosed?
Microscopy and culture of skin lesion
How is sporotrichosis treated?
Itraconazole
How does spirotrichosis appear?
Initially a primary lesion is developed distally and secondary lesions develop along lymphatic drainage.
What other infections have a similar appearance to sporotrichosis?
Mycobacterium marinum
Nocardia species
What causes chromoblastomycosis?
Few different fungi (Cladophilophora carrionii, Fonsecaea pedrosi, Phialophora verrucosa and more)
These fungi get into the skin via inoculation injury and develop over a number of years.
Where is chromoblastomycosis mainly found?
Tropical and subtropical areas
What is the outside appearance of skin that is infected with chromoblastomycosis?
Huge cauliflower-like masses appear that present over long periods of time
How is chromoblastomycosis diagnosed?
Microscopy and culture
What other fungi can cause cutaneous mycosis?
Hyalohyphomycosis (group of opportunistic mycotic infections caused by non-dematiaceous moulds)
Phaeohyphomycosis (caused by deatiaceous (black) moulds
Summary:
Many causes of rash:
History is important (exposure, travel, PMH)
Imporant to be able to describe a rash properly
Cutaneous fungal infections:
Generally localized and self-limiting
Disseminated disease can occur in immunosuppressed patients
Caused by a diverse range of fungi with widely different presentations.
Tissue diagnosis for both histopathology and microscopy are important for confirming a diagnosis and treatment.
