Fungal Infections Of The Skin Flashcards
What is the definition of a fungi?
Aerobic organisms that form a cell wall and grow on or in organic material, forming a colony and reproducing either sexually or asexually
What are the 2 classes of fungi?
Dermatophytes
Yeasts
What are the 3 subclasses of dermatophytes?
Tricophyton
Microsporum
Epidermophyton
What are the 2 subclasses of yeasts?
Candida albicans
Malasezia furfur
What are the 3 types of superficial fungal infections?
Candida species
Malassezia species
Dermatophytes
How do superficial fungal infections form?
Capable of colonising (cutaneous microbiome) and superficially invading skin and mucosal sites
When do deeper, chronic cutaneous fungal infections occur?
After percutaneous inoculation
what are some examples of deeper, chronic fungal infections?
Phaeohyphomycosis, sporotrichosis
When do systemic fungal infections occur?
Most often with host defence defects. Primary lung infection disseminates hematogenously to multiple organs systems including the skin
What ids the aetiology of fungal infections?
Nature of fungus
Human host age, gender and race
Immune status of host
Contributing factors - macearation, occlusion, minor skin trauma
What is the diagnostic approach for fungal infections?
Clinical diagnosis
• Microscopic examination (KOH examination)
• Culture
• Wood light examination (UV light–365nm)
• Skin biopsy
• Trichophytin test
• PCR
• ELISA
What is the clinical presentation of Dermatophytes?
Infection of skin, hair and nails caused by dermatophytes (fungi that live within the epidermal keratin or hair follicle and do not penetrate into deeper structures)
What is the pathophysiology of Dermatophytes?
Digestion of keratin by Dermatophytes results in scaly skin, broken hairs, crumbling nails
Which investigations are useful for Dermatophytes?
Skin scrapings
Hair and or nail clippings analysed with potassium hydroxide prep to look for hyphae and mycelia
What are the different types of dermatotyphoses?
Tinea Capitis
• Tinea Barbae
• Tinea Faciei
• Tinea Corporis
• Tinea Cruris (inguinalis)
• Tinea Manus
• Tinea Pedis
• Tinea Unguium (Onychomycosis)
What are the clinical features of tinia capitis?
Area of erythema and scale with local hair loss
Border is usually sharply defined and inflammed
What is Kerion Celsi? (Caused by tinea capitis)
Massive destruction of follicles, producing a boggy nodule with pustules, sinus tracts and drainage
What is the diagnostic approach for tinia capitis and Kerion celsi?
Potassium hydroxide examination of scales or plucked hairs, as well as cultures
What will the examination show for most microsporum?
Greenish fluorescence with a wood light
What are the clinical findings for tinea favosa? (Most severe form of tinea capitis)
Children are mostly affected
Mild forms - erythema and loss of hair luster
As disease progresses - erythema and typical scutula (compact accumulations of yellow scales and crusts) appear which leads to scarring
Most intense cases - extensive scarring alopecia with peripheral active disease and unpleasant odour
What is the treatment for tinea capitis?
Fluconazole 6mg/kg/day for 3 weeks
Itraconazole - 5mg/kg/day for 4 weeks
Terbinafine - 125mg/day (25kg weight), 187.5mg/day (25-35kg weight), 250mg/day (>35kg weight) for 6 weeks
Griseofulvin 20-25mg/kg/day for 6-8 weeks (up to 16 weeks)
What is tinea Barbae?
Disease of men and almost always occurs in farmers, vets, and other exposure to large animals
What are the clinical findings of tinea barbae?
Severe, deep folliculitis with erythema, modular infiltrates, scales and pustules
Deep furunculoid nodules, still coated with pustules develop
what is the rule for tinea barbae?
Marked regional lymphadenopathy
What typically happens to tinea barbae after 4-6 weeks?
Spontaneous resolution with immunity
What is the diagnosis for tinea barbae?
Epilated hairs in potassium hydroxide examination and culture
What is the most likely cause of tinea faciei? (Ringworm)
Patients who sleep in very close contact with their pets, especially small children and women
Which pets are the biggest carriers of tinea faciei?
Cats and dogs
Which fungi produces tinea faciei?
Zoophilic fungi
What is the clinical manifestation of tinea faciei?
Annular or serpiginous lesions (wavy margins)
Which dermatophytes can cause tinea corporis?
Almost all dermatophytes
What is the clinical manifestation of tinea corporis?
Lesions which are sharply bordered, peripherally spreading, slightly indurated (hardened) patch or plaque
Border is often redder with prominent scale and pustules
Scales are usually at the leading edge, pointing towards normal skin
Older, central lesions typically resolve as periphery advances
Are men or women more likely to be infected by tinea cruris?
Men far more likely
What should one check if they also have tinea pedis?
Check the feet of all patients with groin rashes
What are some risk factors for tinea cruris?
Obesity
Inadequate personal hygiene
Hyperhydrosis
Prolonged sitting on plastic or non absorbent surfaces
Tight synthetic clothing
Diabetes mellitus
What is the clinical manifestation of tinea cruris?
Slowly spreading erythematous patches with scaly borders most often found on upper inner aspects of thigh, where scrotum touches leg
Occasionally disease spreads to scrotum, perineum, perianal area, and gluteal cleft
What is another name for tinea pedis?
Athletes foot
Which climates is tinea pedis more common in?
Warmer, moister climates
How is tinea pedis caught?
The spores of the dermatophytes survive for months in shoes, carpets, bath mats, locker rooms and showers
What are risk factors for tinea pedis?
Reduced hygiene
Advanced age
Hyperhydrosis
Warm and moist environment
Impaired peripheral blood flow
What are some preventative measures for tinea pedis?
Using rubber sandals in community showers
Carefully drying feet especially between toes
Wearing clean socks and shoes
What are the 3 types of tines pedis?
Interdigital
Hyperkeratotic
Dyshydrotic
Where is tinea pedis the interdigital type commonly found?
Predominantly in the lateral 2 toe webs due to being the tightest interdigital spaces
Will find grey white swollen skin between the toes
When the macerated skin is removed, erosions, fissures and erythema may be prominent
Process often extends to the sole
What are the 3 aggregating factors in the interdigital type?
Hyperhydrosis
Gram negative toe web infections
What almost always causes the hyper keratotic or moccasin type of tinea pedis?
T. Rubrum and usually accompanied by tinea unguium
What are the clinical features of the hyperkeratotic type of tinea pedis?
Thick scales, tropic all covering the heels, the tips of the toes and metacarpal pads
What can be seen upon closer examination of hyperkeratotic tinea pedis?
Erythema at the advancing border may be seen