Mycoses and Dermatophytoses Overview

Mycoses Categories

• Mycoses are categorized into cutaneous, subcutaneous, systemic, and opportunistic.
• Cutaneous mycoses specifically affect the keratinized layers of skin, hair, or nails. Superficial cutaneous mycoses, specifically dermatophytoses, are included in this category.
• Subcutaneous mycoses involve deeper skin layers.
• Systemic mycoses affect multiple organ systems.
• Opportunistic mycoses affect individuals with weakened immune systems.

Dermatophytoses

• Dermatophytoses affect the keratinized layers of the skin, hair, or nails.
• Symptoms include itching, scaling, ring-like skin patches, brittle and broken hair, and thick discoloured nails.
• Dermatophytes are keratinophilic (keratin-loving).
• Ringworm is a common name for dermatophytosis, named by the Greeks and Romans.

Dermatophytosis Classification

• Dermatophytes are classified by their usual habitat: anthropophilic, geophilic, or zoophilic.
• Anthropophilic dermatophytes infect humans.
• Geophilic dermatophytes inhabit the soil and infect humans.
• Zoophilic dermatophytes infect animals, but can also infect humans.

Dermatophytes Involved in Ringworm

• Three anamorphic genera are involved in ringworm: Microsporum, Epidermophyton, and Trichophyton.
• Microsporum species infect hair and skin only.
• Epidermophyton species attack skin and nails only.
• Trichophyton species attack skin, hair, or nails.

Pathogenesis and Immunity in Dermatophytosis

• Contact and trauma can contribute.
• Moisture plays a role in infection.
• Crowded living conditions can increase risk.
• Cellular immunodeficiency makes individuals more susceptible.
• Chronic inflammation can worsen infection.
• Re-infection is possible, but requires a larger inoculum.

Sites of Common Ringworm Infections

• Schools
• Military camps
• Prisons
• Warm damp areas
• Animals

Modes of Transmission

• Close human contact.
• Sharing of items like clothes, combs, brushes, towels, and bedsheets (fomites).
• Animal-to-human contact (zoophilic).

Types of Ringworm and Affected Sites

• Tinea capitis affects the head, scalp, eyebrows, and eyelashes.
• Tinea facialis affects the face.
• Tinea corporis affects the body.
• Tinea cruris affects the groin (jock itch).
• Tinea unguium affects the nails.
• Tinea barbae affects the beard.
• Tinea manuum affects the hands.
• Tinea pedis affects the feet (athlete's foot).
• Tinea imbricata shows distinctive lesions.

Tinea capitis Clinical Presentations

• Endothrix (black dot): Fungal elements invade hair without destroying the cuticle, often associated with a black dot appearance on the scalp.
• Ectothrix (gray patch): Fungal elements destroy the hair cuticle; hyphae are then converted into infectious arthroconidia. Small well-defined patches are common.
• Kerion: A complication of scalp ringworm caused by an overzealous immune response. The condition involves painful and inflamed nodules and plaques. Usually, of animal origin. Kerion heals, but potentially leaves some scarring.
• Favus/Tinea favosa: This is the severe form of tinea capitis, characterized by the invasion of hair by hyphae. Common symptoms include yellow crusts (scutula) on the scalp, and a foetid odour.

Tinea corporis - Clinical Symptoms

• Typically restricted to the stratum corneum of smooth skin.
• Skin lesions form concentric or ring-like lesions.
• Lesions may become inflamed.

Tinea cruris - Clinical Symptoms

• Lesions tend to be circinate (ring-shaped) and serpiginous (snake-like)
• Often found on the groin, inner thighs, and scrotum.
• Factors like persistent perspiration, high humidity, tight clothing, and diabetes can exacerbate it.

Tinea cruris predisposing factors

• Persistent perspiration
• High humidity
• Tight clothing
• Diabetes
• Obesity
• Topical glucocorticoid application

Three Anamorphic Genera Involved in Ringworm

• Microsporum: infects hair and skin only
• Epidermophyton: attacks skin and nails only
• Trichophyton: attacks skin, hair or nails.
• Microsporum audouinii, M. canis, M. ferrugineum, and M. gypseum are included as Microsporum species.
• Ringworm species include T. concentricum, T. mentagrophytes, T. rubrum, T. tonsurans, T. violaceum, T. verrucosum, and T. schoenleinii.

Tinea unguium- Clinical Symptoms

• Infection typically begins at the edges of the nail plate.
• Paronychia (inflammation around the nail) arises.
• T. rubrum, T. mentagrophytes, and E. floccosum are common causative agents.

Tinea barbae- Clinical Symptoms

• Commonly present in farm workers
• Inflammatory lesions are common
• T. mentagrophytes is the common causative organism.

Tinea manuum- Clinical Symptoms

• Dermatophyte infection of the hands.
• Zoophilic or geophilic fungus can cause it.
• Anthropophilic fungus is usually the culprit.

Tinea pedis- Clinical Symptoms

• Infection typically occurs between the toes or in toe webs.
• It often releases clear fluid.
• Common in the 4th and 5th toes.
• Pruritic (itchy), scaly soles and painful fissures between toes are often found.
• T. mentagrophytes, T. rubrum, and E. floccosum can be causative agents.

Hair Penetration Test- Procedure

• Examining the scalp or affected area for fungal infections.
• Cleaning the area to remove oils or debris.
• Collecting hair strands using tweezers as close to the scalp as possible.
• Microscopic examination of the hair sample using KOH (potassium hydroxide)
• Observing for fungal hyphae or conidia inside the hair shaft.

Hair Penetration Test- Positive and Negative Results

• Positive result: Fungal hyphae or conidia present inside hair shaft. This indicates fungal infection of the hair itself.
• Negative result: No fungal elements seen inside the hair shaft. Infection is limited to the outer layers of the skin and does not involve the hair shaft.

Hair Penetration Test- Characteristics of Culture, Test and Microscopic Features

• T. mentagrophytes: Positive in hair perforation test; microscopic features include tear-drop microconidia; culture positive in urea test.
• T. rubrum: Negative in hair perforation test; microscopic features include clavate or peg-shaped microconidia; urea test negative.

This quiz explores the categories of mycoses, including cutaneous, subcutaneous, systemic, and opportunistic forms. It also delves into dermatophytoses, focusing on their symptoms, classification, and the characteristics of dermatophytes. Test your knowledge on fungal infections and their classifications.