Fungal Skin Infections Midterm Notes PDF

**INTEGUMENTARY - *Fungal Skin Infections*** **1. Tinea Infections (Dermatophytosis)** **Tinea infections** are superficial fungal infections of the skin caused by dermatophytes. These infections are classified based on the location of infection. - **Cause**: - **Dermatophytes**: Fungi t...

**INTEGUMENTARY - *Fungal Skin Infections*** **1. Tinea Infections (Dermatophytosis)** **Tinea infections** are superficial fungal infections of the skin caused by dermatophytes. These infections are classified based on the location of infection. - **Cause**: - **Dermatophytes**: Fungi that infect keratinized tissues such as skin, hair, and nails. - Common species include **Trichophyton, Microsporum, and Epidermophyton**. - **Pathophysiology**: - Dermatophytes infect the **stratum corneum** of the skin, hair, or nails. - These fungi produce **keratinase enzymes** that degrade keratin, allowing the fungus to use it as a food source. - This triggers an **immune response** involving cytokine release, neutrophil recruitment, and local inflammation, resulting in **itchy, scaly, and erythematous lesions** on the skin. - **Transmission**: - **Direct contact** with infected individuals, animals (like pets), or contaminated surfaces (e.g., locker rooms, shared towels, clothing, or bedding). - **Autoinoculation**: Scratching an infected area can spread the fungus to other body parts. - **Risk Factors**: - **Warm, moist environments** (like locker rooms, public showers, and swimming pools) promote fungal growth. - Wearing **tight-fitting, occlusive clothing**. - **Excessive sweating** (hyperhidrosis) and failure to dry the skin thoroughly. - **Compromised immune system** (e.g., HIV, diabetes) increases susceptibility to fungal infections【118:1†source】. **2. Tinea Capitis (Scalp Infection)** - **Cause**: Caused by dermatophytes such as **Trichophyton tonsurans** and **Microsporum canis**. - **Pathophysiology**: - The fungus invades the **scalp\'s stratum corneum** and hair follicles. - It weakens the hair shaft, leading to **hair breakage** and **scaly, itchy scalp lesions**. - Can result in **kerion**, a boggy, inflamed, and pustular mass caused by an exaggerated immune response. - **Transmission**: - **Person-to-person transmission** via contaminated combs, hats, or hairbrushes. - **Animal-to-human transmission** from infected animals like cats, dogs, and livestock. - **Risk Factors**: - Children are at a higher risk than adults. - **Close contact** with infected people or animals. - **Poor hygiene** and overcrowded living conditions. **3. Tinea Pedis (Athlete's Foot)** - **Cause**: Caused by dermatophytes such as **Trichophyton rubrum**, **T. mentagrophytes**, and **Epidermophyton floccosum**. - **Pathophysiology**: - The fungus infects the **stratum corneum** of the feet, particularly in the web spaces between the toes. - **Hyperkeratosis and scaling** develop as the immune system responds to the infection. - If left untreated, it can cause fissures and bacterial superinfections. - **Transmission**: - **Walking barefoot** in warm, moist public areas (locker rooms, showers, swimming pools). - **Direct contact** with contaminated footwear or towels. - **Risk Factors**: - **Sweaty feet** and wearing **tight, non-breathable shoes**. - **Poor hygiene**, such as not drying feet properly after bathing. - **Shared use of footwear** (e.g., rental shoes). **4. Tinea Corporis (Ringworm)** - **Cause**: Caused by dermatophytes like **Trichophyton rubrum** and **Microsporum canis**. - **Pathophysiology**: - The infection is limited to the **stratum corneum** of the skin. - It produces the classic **circular, red, scaly lesion with a central clearing**. - The infection spreads outward while the center of the lesion clears as the immune system suppresses fungal growth. - **Transmission**: - **Direct contact** with infected animals, humans, or contaminated surfaces. - **Fomites** such as clothing, towels, or gym equipment may also act as transmission vectors. - **Risk Factors**: - Contact with **infected animals** (common in children). - **Contact sports** like wrestling. - **Warm, humid climates** and shared use of gym equipment or towels. **5. Tinea Cruris (Jock Itch)** - **Cause**: Caused by dermatophytes like **Trichophyton rubrum** and **Epidermophyton floccosum**. - **Pathophysiology**: - The infection occurs in the **groin and inner thigh**. - Fungal invasion of keratinized tissues leads to **red, scaly, itchy lesions** with sharp borders. - Chronic scratching may lead to lichenification (thickened, leathery skin). - **Transmission**: - **Person-to-person transmission** or contact with contaminated items like clothing, towels, or underwear. - **Autoinoculation** from other infected body parts, such as feet (athlete's foot. - **Risk Factors**: - **Warm, humid climates**, excessive sweating, and tight clothing (like athletic wear). - **Overweight individuals** with large skin folds are at higher risk. - **Athletes** or those frequently in locker rooms and communal showers. **6. Tinea Unguium (Onychomycosis)** - **Cause**: Caused by dermatophytes like **Trichophyton rubrum** and **T. mentagrophytes**. - **Pathophysiology**: - The fungus invades the **nail bed and nail plate**, digesting keratin. - This causes **thickened, discolored, brittle nails**. - Chronic infections can lead to **onycholysis** (nail detachment from the nail bed). - **Transmission**: - **Direct contact** with infected nails or surfaces. - Can result from **autoinoculation** from tinea pedis (athlete's foot). - **Risk Factors**: - **Older age** and having **diabetes** or **peripheral vascular disease**. - **Exposure to moist environments**, such as public pools or communal showers. - **Nail trauma** or the use of **artificial nails**. **7. Candidiasis (Yeast Infection)** - **Cause**: Caused by **Candida albicans**, a yeast-like fungus that is normally part of the body\'s microbiota. - **Pathophysiology**: - Candida invades the **epidermal barrier** using **keratolytic proteases and enzymes**, breaking down keratin. - Infection occurs in warm, moist areas, such as **skin folds, oral cavity (thrush), and genital areas**. - Triggers an **inflammatory immune response**, resulting in **red, erythematous, itchy, and eroded lesions**. - **Transmission**: - Typically a result of **overgrowth** due to **altered immune status**, antibiotic use, or increased skin moisture. - **Autoinfection** occurs as Candida shifts from a **commensal** to a **pathogenic state** in susceptible individuals. - **Risk Factors**: - **Immunosuppression** (e.g., HIV, chemotherapy). - Use of **broad-spectrum antibiotics**. - **Warm, moist environments**. - **Poor hygiene** and **obesity** (due to large skin folds).