Infezione causata da dermatofiti delle specie Microsporum, Trichophyton and Epidermophyton. Trasmissione uomo-uomo e animale-uomo (più infiammatoria).
Le micosi spesso vengono suddivise in tre tipi: da Dermatofiti, Lieviti o Muffe .
2.3.1 Infezioni da dermatofiti
Definizione
Eziologia; Patogenesi
Distinzione tra micosi primaria (patogeni obbligati in grado di invadere tessuti sani) e micosi secondaria (il tessuto deve essere danneggiato, da agenti chimici, in corso di malattie endocine, malattie gravi, malattie autoimmuni, medicazioni)
Sintomi
Scalp:
- Trichophyton infections: start in hair follicle; fungal growth in and around hair. Deep nodular infiltrates with abscesses and/or pustules. Painful. Examples: tinea barbae, tinea capitis in children.
- Favus: starts in hair follicle, evolves with distinctive scale (= scutula, yellow, 2-4mm serocrusts with central dell around hair). When removed -> weeping erosions. Green fluorescence under Wood light. Unpleasant smell compared to cheese or mouse urine. Usually on scalp of children. May be chronic with destruction of hair follicles leading to scarring alopecia.
- Microsporum infections: typical "ring worm", circular areas of hair loss with scales and broken-off hairs (black dots). Fungus confined to hairs. Green fluorescence under Wood light. Highly contagious. Usually on scalp of children. Alopecia reversible.
Palms and soles:
- Vesicular, circumscribed, unilateral.
- Fine scales, unilateral, later bilateral (tinea lamellosa sicca).
Nails:
- Onychomycoses: predisposing factor: impaired nail growth (improper shoes, trauma). Eponychial form (5%) -> opaque, roughened nail plate, primarily lateral and proximal. Hyponychial form (95%) -> distortion and loosening of nail plate, usually starting distal.
Other sites:
- Erythematous, circulation sharply bordered plaques with peripheral scale (spreading of fungus in stratum corneum). Centrifugal growth with central clearing.
- Variable pruritus
- Sometimes pustular, inflammatory form, usually with zoophilic fungi (= acquired from animals)
Localisation
See classification and symptoms.
Classificazione
Basata sulla localizzazione (senza tenere in considerazione l'agente causale):
- Tinea corporis
- Tinea capitis
- Tinea faciei
- Tinea barbae
- Tinea cruris
- Tinea inguinalis
- Tinea manus
- Tinea pedis
- Tinea unguium (onicomicosis)
- Tinea nigra (Exophiala werneckii)
Laboratorio
Identificazione del fungo (esame microscopico con KOH > risultato immediato; esame colturale > impiega 3-4 settimana).
Diagnosi
Caratteristiche cliniche, laboratorio di micologia.
Diagnosi differenziale
Pioderma, dermatite, psoriasis.
Terapia
- Generale: correggere i fattori predisponenti factors (sudore, scarpe non adatte).
- Topica: la scelta del veicolo per l'antimicotico dipende dalla localizzazione e dalle caratteristiche cliniche.
Antisettici: Soluzione di Castellani, solfato ossichinolonico (1:1000).Antimicotici (antifungini): imidazoli, allilamine, cicloproxamina, amorolfina.Cheratolitici:acido salicilico, urea (unchie, capelli). Tintura di Fabry (acido salicilico, fenolol).Formalina per disinfectare le scrape. - Terapia sistemica: imidazoli (itraconazolo, fluconazolo), allylamines (terbinafina), griseofulvina.
Diagnosi differenziale
Tests
- This farmer spent August at a Alpine mountain farm cabin with his cows and a few mosquitoes. The skin lesion shown in the picture appeared in mid-August. It is asymptomatic but spreading. What is your diagnosis?
- A 20-year-old woman with hay fever has three house cats. The pictured lesion has been present for 3 weeks. Which additional studies are required?
- What are the differential diagnostic considerations here?
- What are the possible causes of this nail dystrophy?
- Which of these factor predispose to tinea capitis?
- Statement 1 If tinea capitis is suspected, the scalp should be examined with Wood light
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