Skin Injury Factors and Lesions

Factors Causing Skin Injury

• External (exogenous) factors include environmental influences.
• Internal (endogenous) factors arise from within the body.

Types of Skin Lesions

• Primary lesions: Direct results of disease, crucial for diagnosis.
• Secondary lesions: Evolve from primary lesions, usually less diagnostically significant.

Primary Skin Lesions

• Macule: Discolored area, ≤ 1 cm; example: lentigo, a benign hyperpigmentation.
• Papule: Small, round, solid elevation, ≤ 1 cm in size.
• Plaque: Larger, flat-topped solid elevation of the skin.
• Nodule: Hard elevation, ≥ 1 cm, extends into deeper skin layers.
• Vesicle: Circumscribed elevation of < 1 cm filled with clear fluid.
• Bulla: Larger vesicle (> 1 cm) containing fluid within the epidermis.
• Tumor: Large mass implicating neoplasia, affecting skin or subcutis.
• Cyst: Epithelial-lined cavity with fluid or solid material.
• Pustule: Small, pus-filled elevation of the epidermis.
• Abscess: Accumulation of pus within epidermis or hair follicle.
• Wheal: Smooth, well-defined elevation from dermal edema, commonly seen in allergic reactions.

Secondary Skin Lesions

• Scale: Accumulation of flakes or dandruff on the skin surface.
• Crust: Dried exudate, blood, or serum accumulation.
• Comedo: Dilated hair follicle filled with cornified cells; often seen in conditions like hyperadrenocorticism.

Hair Abnormalities

• Alopecia: Loss of hair.
• Hypotrichosis: Less hair than normal.
• Atrichia: Absence of hair due to failure of development.
• Effluvium/defluxion: Excessive shedding.
• Hypertrichosis (hirsutism): More hair than usual; can be due to endocrine disorders.

Epidermal Pigmentation Alterations

• Hyperpigmentation: Increased melanin production, often due to inflammation or genetics.
• Hypopigmentation: Reduced melanin, can be congenital or due to melanocyte dysfunction.
• Pigmentation incontinence: Loss of melanin from the basal epidermis.

Secondary Lesion Characteristics

• Epidermal collarette: Circular rim of keratin flakes after vesicle/pustule loss.
• Ulcer: Break in the epidermis, exposing underlying dermis.
• Excoriation: Erosions or ulcers from scratching or trauma.
• Scar: Fibrous tissue replacing damaged skin.
• Fissure: Linear cracks in thickened, inelastic skin.
• Lichenification: Thickening and hardening of skin with visible superficial markings.

Explore the factors that cause skin injuries, both external and internal. This quiz delves into the gross morphology of skin lesions, distinguishing between primary and secondary lesions. Gain insight into the diagnostic significance of these conditions.