Mycoses Overview and Keratitis

Mycoses Overview

• Mycoses are fungal diseases, generally chronic.
• Factors like diabetes, cancer, alcoholism, AIDS, surgery and immunosuppressive/antibiotic use can increase the risk of systemic mycoses.
• Sporotrichosis has a distinctive clinical presentation with lesions aligned along lymphatic vessels.

Categories of Mycoses

• Cutaneous mycoses include superficial mycoses and dermatophytoses.
• Subcutaneous mycoses are infections below the skin's surface.
• Systemic mycoses spread to multiple organs within the body.
• Opportunistic mycoses affect individuals with weakened immune systems.

Superficial Mycoses

• Keratitis is a fungal infection affecting the cornea of the eye.
• It can lead to vision loss.
• Common causative agents include Fusarium, Aspergillus, Curvularia, Penicillium, Cephalosporium, and Candida.

Keratitis

• Microscopic exam reveals molds (except Candida).
• Candida appears as yeast cells with pseudohyphae strands.
• Clinical presentation involves a white plaque on the cornea that slowly progresses to ulceration.
• Satellite lesions and endothelial plaques develop in the eye due to fungal involvement.
• Vision impairment is a common outcome.

Keratitis Therapy

• Topical application of drugs like Amphotericin B is toxic to the retina.
• Natamycin (5-fluorocytosine or 5% pimaricin) is the preferred treatment but is expensive and difficult to obtain.

Otomycosis

• Otomycosis, also known as fungus ear or mycotic otitis externa, is a chronic fungal infection of the outer ear and ear canal.
• Aspergillus, Mucor, Penicillium, and Rhizopus are the most common causative agents.
• Initial presentation is often mild irritation that progresses to inflammation and pus production.
• Debris accumulates inside the ear canal.

Otomycosis Therapy

• Clean and aerate the ear canal using a cotton swab saturated with Burrow's Solution.

Superficial Mycoses: Non-dermatophytic Tinea

• Tinea versicolor (Pityriasis Versicolor): Characterized by discolorations or depigmentation with scaling on the skin.
  • Appears in those with dark complexions or those who do not tan.
  • Caused by Malassezia furfur, a common endogenous skin colonizer.
• Tinea nigra: Characterized by brown to black macular patches, primarily on the palms.
  • Differentiate from melanoma through biopsy and culture.
  • Caused by Phaeoannellomyces werneckii.
• Piedra: Characterized by nodules attached to the hair shaft (a cement-like substance).
• Black Piedra: Caused by Piedraia hortae (hard, dark brown to black gritty nodules).
• White Piedra: Caused by Trichophyton ovoides/Trichophyton beigelli/Trichophyton inkin/Trichophyton cutaneum.

Malassezia furfur

• Temporary remedy: 1% Selenium Sulfide.
• Other associated skin diseases include folliculitis, obstructive dacryocystitis, and seborrheic dermatitis among immunocompromised individuals (e.g., AIDS patients) receiving total parenteral nutrition (TPN).

Hortaea werneckii

• Similar clinical presentation to other conditions, potentially leading to misdiagnosis and unnecessary surgery.
• Often confused with melanoma.
• Flat lesion, lack of scaling, and absence of inflammation.
• Colonies are shiny, moist, and a yeast-like structure and may change color to olive-greenish black.

Hortaea werneckii Therapy

• Topical treatments such as mixture of 3% sulphur and 3% salicylic acid, tincture of iodine, weak Whitfield's ointment, and 20-30% sodium thiosulfate.

Trichosporon spp.

• Systemic diseases caused by Trichosporon are frequently fatal.
• Most common clinical consequences is non-specific fever or pneumonia.
• Trichosporon asahaii and Trichosporon mucoides cause specific systemic diseases.
• Microscopy: interwoven, septate hyphae with characteristic oval, rectangular arthroconidia formation in KOH mounting, or fungal media
• Colonies are typically straw, cream or yeast-like, varying from smooth to wrinkled, dry to moist.
• Biochemical tests essential for species identification.

Additional information, image analysis, and case studies (not included in the structured notes).

• Images of different fungi, including fungal cultures, and microscopic images of the fungi are referenced throughout the slides
• Clinical presentations with images of affected skin areas and hair.
• Information about how to identify fungi using a potassium hydroxide (KOH) preparation and Wood's lamp.
• Methods for culturing fungi and interpreting the results of cultures.

This quiz covers the essential concepts of mycoses, their categories, and specific infections like keratitis. It highlights the factors increasing the risk for systemic mycoses and the clinical presentations of various fungal diseases. Test your knowledge on the distinctions between cutaneous, subcutaneous, and opportunistic mycoses.