Primary And Secondary Skin Lesions PDF

**Primary and Secondary Skin Lesions** **Primary skin lesions** develop as a direct result of the disease process. Common examples of primary skin lesions include: - **Macule:** A flat, circumscribed area of discoloration less than 1 cm in diameter. Examples include freckles, flat moles, pet...

**Primary and Secondary Skin Lesions** **Primary skin lesions** develop as a direct result of the disease process. Common examples of primary skin lesions include: - **Macule:** A flat, circumscribed area of discoloration less than 1 cm in diameter. Examples include freckles, flat moles, petechiae, measles, and scarlet fever. - **Patch:** Similar to a macule, but larger than 1 cm in diameter. Examples include vitiligo, port-wine stains, mongolian spots, and café au lait spots. - **Papule:** An elevated, firm, circumscribed area less than 1 cm in diameter. Examples include warts, elevated moles, lichen planus, fibroma, and insect bites. - **Plaque:** An elevated, firm, rough lesion with a flat top surface greater than 1 cm in diameter. Examples include psoriasis, seborrheic keratoses, and actinic keratoses. - **Nodule:** Elevated, firm, circumscribed lesion; deeper in the dermis than a papule; 1-2 cm in diameter. Examples include erythema nodosum and lipomas. - **Tumor:** An elevated, solid lesion; may be clearly demarcated; deeper in the dermis; more than 2 cm in diameter. Examples include neoplasms, benign tumors, lipomas, neurofibromas, and hemangiomas. - **Vesicle:** An elevated, circumscribed, superficial, fluid-filled lesion less than 1 cm in diameter. Examples include varicella (chickenpox), herpes zoster (shingles), and herpes simplex. - **Bulla:** A vesicle larger than 1 cm in diameter. Examples include blisters and pemphigus vulgaris. - **Pustule:** An elevated, superficial lesion similar to a vesicle but filled with purulent fluid. Examples include impetigo and acne. - **Cyst:** An elevated, circumscribed, encapsulated lesion in the dermis or subcutaneous layer filled with liquid or semisolid material. Examples include sebaceous cysts and cystic acne. **Secondary skin lesions** result from changes in primary lesions or from external factors such as scratching or infection. Common examples of secondary skin lesions include: - **Scale:** Heaped-up, keratinized cells; flaky skin. Examples include flaking of the skin after scarlet fever or a drug reaction and dry skin. - **Crust:** Dried serum, blood, or pus on the skin surface. - **Erosion:** Loss of part of the epidermis. Examples include chemical injury. - **Ulcer:** Loss of epidermis and dermis. Examples include pressure ulcers and stasis ulcers. - **Fissure:** A linear crack or break from the epidermis to the dermis. Examples include athlete's foot, cracks at the corners of the mouth, and anal fissures. - **Atrophy:** Thinning of the skin surface and loss of skin markings. Examples include aged skin and striae. - **Scar:** A thin to thick fibrous tissue that replaces normal skin after injury to the dermis. Examples include healed wounds or surgical incisions. - **Keloid:** An irregularly shaped, elevated, progressively enlarging scar caused by excessive collagen formation during healing. - **Lichenification:** Rough, thickened epidermis secondary to persistent rubbing, itching, or skin irritation. Examples include chronic dermatitis. - **Excoriation:** Loss of epidermis; linear, hollowed-out, crusted area. Examples include abrasions, scratches, and scabies. **Inflammatory Skin Disorders** **Inflammatory skin disorders** are a group of conditions that cause inflammation of the skin. The most common inflammatory disorders are eczema and dermatitis. **Contact dermatitis** occurs when the skin comes into contact with an irritant or allergen. There are two main types of contact dermatitis: allergic contact dermatitis (ACD) and irritant contact dermatitis (ICD). - **Allergic contact dermatitis** is a type IV delayed hypersensitivity reaction that occurs when the skin comes into contact with an allergen. Common allergens include microorganisms, chemicals, foreign proteins, latex, drugs, and metals. - **Irritant contact dermatitis** is a non-specific inflammatory reaction caused by the direct cytotoxic action of a substance on the skin. ICD is not mediated by the immune system. The severity of the inflammation is related to the concentration of the irritant, length of exposure, and disruption of the skin barrier. Common irritants include water, detergents, solvents, acids, alkalis, fiberglass, dust, metal salts, insecticides, herbicides, dyes, fragrances, and preservatives. **Atopic dermatitis** is a chronic inflammatory skin condition characterized by dry, itchy skin. It is often associated with a family history of atopic conditions such as asthma, hay fever, and eczema. The cause of atopic dermatitis is not fully understood, but it is thought to be a combination of genetic and environmental factors. **[Comparison of Contact Dermatitis and Atopic Dermatitis]** **Feature** **Contact Dermatitis** **Atopic Dermatitis** ----------------------------- ---------------------------------------------- -------------------------------------------------------------------- **Cause** Exposure to an irritant or allergen Unknown, likely a combination of genetic and environmental factors **Mechanism** Allergic (ACD) or non-allergic (ICD) Immune dysregulation **Clinical Manifestations** Erythema, edema, pruritis, vesicular lesions Dry, itchy skin, erythema, scaling, lichenification **Distribution** Localized to area of contact Flexural surfaces (e.g., elbows, knees, neck) **Papulosquamous Skin Disorders** **Papulosquamous skin disorders** are characterized by the development of papules, scales, plaques, and erythema. **Psoriasis** is a chronic, relapsing, proliferative, immune-mediated inflammatory disorder that involves the skin, scalp, and nails. It is thought to be caused by a combination of genetic and environmental factors. The inflammatory cascade of psoriasis involves complex interactions between macrophages, fibroblasts, dendritic cells, natural killer cells, T-helper cells, and regulatory T cells, leading to the secretion of inflammatory mediators that promote keratinocyte proliferation, angiogenesis, and infiltration of other immune cells into the lesions. **Acne rosacea** is a chronic inflammatory skin condition that most often affects the central face. The exact cause is unknown, but genetic factors, immune dysregulation, and neurovascular dysregulation are involved. Triggers for rosacea include chronic sun exposure and damage, heat, alcohol consumption, hormonal fluctuations, and stress. **Acne vulgaris** is an inflammatory disorder of the pilosebaceous follicle, the sebaceous gland contiguous with a hair follicle, that usually occurs during adolescence. **Lichen planus (LP)** is a benign autoimmune inflammatory disorder that can affect the skin, nails, and mucous membranes. The cause is unknown, but T cells, adhesion molecules, inflammatory cytokines, perforin, and antigen-presenting cells are involved. LP is also linked to drugs and the hepatitis C virus. **Common Bacterial Skin Infections** **Bacterial skin infections** are common and usually caused by local invasion of pathogens. **Causative Microorganisms** The most common causative microorganisms of bacterial skin infections are: - *Staphylococcus aureus* (including methicillin-resistant strains) - Beta-hemolytic streptococci - Group A Streptococcus - *Streptococcus pyogenes* **Types of Bacterial Skin Infections and Their Clinical Manifestations** - **Folliculitis:** An infection of the hair follicle. It typically presents as papules or pustules with a surrounding area of erythema. - **Cellulitis:** An infection of the dermis and subcutaneous tissue. It manifests as an erythematous, warm, edematous, painful area without a distinct border. - **Impetigo:** A superficial skin infection, more common in children, characterized by honey-colored crusted lesions that typically occur around the nose and mouth. **Common Viral Skin Infections** **Varicella-zoster virus (VZV)** causes varicella (chickenpox) and herpes zoster (shingles). VZV is spread via airborne droplets or direct contact with actively shedding lesions. It is highly contagious. - **Chickenpox** manifests as an itchy, blistering rash on the trunk, scalp, or face. - **Shingles** is characterized by painful vesicular eruptions along a dermatome (the area of skin supplied by a single spinal nerve). **Herpes simplex virus (HSV)** causes oral and genital herpes infections. Transmission occurs through contact with infected oral or genital secretions. - **Oral herpes** commonly presents as cold sores or fever blisters around the mouth. - **Genital herpes** involves painful blisters or ulcers in the genital area. **Human papillomavirus (HPV)** causes warts (verrucae). - **Common warts** are typically elevated with a rough, grayish surface. - **Genital warts (condylomata acuminata)** are sexually transmitted and appear as cauliflower-like lesions. **Tinea Infections and Candidiasis** **Tinea infections** and **candidiasis** are common fungal skin infections. **Tinea infections** are caused by dermatophytes, a type of fungi that thrives on keratin. These infections are often called \"ringworm\" due to the characteristic ring-shaped lesions they produce. Transmission occurs via direct contact with the fungus, either from person-to-person or through contact with contaminated objects. **Candidiasis** is caused by the yeast-like fungus *Candida albicans*. *C. albicans* is normally found on mucous membranes, skin, in the gastrointestinal tract, and vagina. It can switch from a commensal organism to a pathogen, especially in individuals who are immunocompromised. **Clinical Manifestations of Tinea Infections and Candidiasis** **Infection** **Clinical Manifestations** --------------------------- -------------------------------------------------------------------------------------- **Tinea capitis** Scaly, pruritic scalp with bald areas; hair breaks easily **Tinea corporis** Circular, scaly patches with a slightly elevated border **Tinea cruris** Erythematous, scaling patches in the groin **Tinea pedis** Scaling, macerated, painful skin between toes **Tinea manuum** Dry, scaly lesions or moist, vesicular lesions on the palms **Oral candidiasis** White plaques or spots in the mouth that can lead to shallow ulcers **Cutaneous candidiasis** Erythematous, pruritic rash in skin folds, such as under the breasts or in the groin **Benign Skin Tumors and Skin Cancer** Some **benign skin tumors**, such as actinic keratosis (AK) and nevi (moles), can develop into skin cancers. **Actinic keratosis (AK)** is a precancerous skin condition that develops on sun-exposed areas of the skin. AKs are caused by chronic exposure to UV radiation. They appear as rough, scaly patches that are often pink or red in color. AKs can progress to squamous cell carcinoma (SCC). **Nevi (moles)** are benign growths of melanocytes, the pigment-producing cells of the skin. They are common and usually harmless, but some nevi can develop into melanoma. Atypical nevi (dysplastic nevi) are more likely to develop into melanoma than common nevi. **[Comparison of Skin Cancers]** **Basal Cell Carcinoma** - **Pathophysiology:** Arises from mutations in the *TP53* tumor-suppressor gene, leading to loss of keratinocyte repair functions and resistance to apoptosis. Primarily associated with the Sonic Hedgehog signaling axis with disinhibition of the *PTCH1* gene. - **Clinical Manifestations:** Pearly or ivory nodule with small blood vessels on the surface (telangiectasias), often with a depressed center and rolled borders. Grows slowly and rarely metastasizes. **Squamous Cell Carcinoma** - **Pathophysiology:** Caused by chronic UV radiation exposure, leading to mutations in the *TP53* gene and other genes involved in DNA repair and apoptosis. - **Clinical Manifestations:** Firm, elevated lesion with a scaly or crusted surface. Can grow rapidly and may metastasize to lymph nodes. **Melanoma** - **Pathophysiology:** Arises from malignant degeneration of melanocytes. Involves mutations that activate oncogenes and inactivate tumor suppressor genes, leading to uncontrolled cell growth. - **Clinical Manifestations:** Variable appearance, often asymmetrical with irregular borders and color variation. Can grow rapidly and metastasize to lymph nodes and distant organs. **The Role of Ultraviolet Radiation in Skin Cancer** **Ultraviolet radiation (UVR)** is a major risk factor for all types of skin cancer. Exposure to UV radiation from the sun and tanning beds can damage DNA in skin cells and suppress the immune system, increasing the risk of skin cancer. UVB radiation is primarily responsible for sunburn, while UVA radiation penetrates deeper into the skin and contributes to premature aging and skin cancer. People with fair skin, light hair, and blue eyes are at increased risk for skin cancer because they have less melanin, the pigment that protects the skin from UV radiation.