Dermatology Quiz on Skin Lesions

Disorders of Hyperpigmentation (1/2)

• Freckles: Small brown/dark macules (flat). Darken in sun exposure. Increased melanin. Normal melanocyte number/density.

• Lentigo: Benign pigmented lesion. Increased number of melanocytes in the basal layer of epidermis. Not affected by UV/sun exposure. Morphology: small, flat, uniform brown, tan or black coloration. Smooth with no scaling or thickening. Commonly on sun-exposed areas (face, hands, forearms). Increased melanocytes at dermal-epidermal junction. No nesting or clustering of melanocytes (distinguishes from melanoma). Hyperpigmentation due to increased melanin production.

• Melanocytic Nevi: Benign neoplasm of melanocytes. Tan/brown pigmented lesions. Uniform color. Often round or oval shape.

Disorders of Hyperpigmentation (2/2)

• Hemosiderin Hyperpigmentation: Brownish skin discoloration. Caused by deposition of hemosiderin (breakdown of hemoglobin). Induration, scaling or atrophy in chronic cases. Occurs in lower extremities (ankles and shins). Symmetrical involvement is common. Secondary to chronic venous insufficiency (CVI). Extravasation of RBCs into the dermis. Macrophages phagocytose hemosiderin. Diagnosis: Clinical based on pigmentation associated with CVI or trauma. Dermoscopy: Hemosiderin deposition. Benign. Indicates underlying venous pathology. Chronic may lead to permanent discoloration or venous ulcers.

• Post-Inflammatory Hyperpigmentation (PIH): Acquired hyperpigmentation after skin injury or inflammation. Abnormal distribution of melanin in epidermis or dermis (skin's inflammatory response). Morphology: Hyperpigmented macules or patches with irregular borders. Color ranges: light brown-black (epidermal)or blue-gray (dermal). Epidermal PIH: Fades over months to years. Dermal PIH: More persistent and harder to treat.

Disorders of Hypo-pigmentation

• Albinism (Oculocutaneous Albinism (OCA)): Family of genetic disorders. Autosomal recessive. Absent/reduced melanin synthesis in melanocytes. Normal number of melanocytes. Most common forms: decrease tyrosinase activity. Hypopigmentation of hair, skin, eyes. White hair, pink skin color, blue eyes. Increased risk of sunburns, Increased risk of skin cancer, No UV light protection.

• Vitiligo: Acquired, localized pigment disorder. Autoimmune destruction of melanocytes.

• Idiopathic Hypomelanosis (IGH): Benign condition. Asymptomatic depigmented (white) macules/patches. No clinical signs of inflammation (warmth). Treatment: steroids, immunosuppressants. Dark skinned individuals: Obvious areas of depigmentation. Light skinned individuals: Failure to tan in localized region.

Other Disorders of Skin Pigmentation

• Multiple small, round or oval, hypopigmented macules. Seen in middle-aged and older adults. Results from chronic sun exposure and aging.
• Affects sun-exposed areas of skin. Hypopigmented macules (lighter than surrounding skin). Smooth surface with no scaling or atrophy.

Benign Epithelial Tumors

• Seborrheic Keratosis: Common benign tumors. Proliferation of immature keratinocytes. Arise spontaneously. Commonly on the trunk. Flat, well-demarcated, round or oval. Dark, velvety surface, appear "stuck on."

• Acanthosis Nigricans: Hyperpigmented (dark) plaques on skin. Intertriginous sites (folds). Associated with insulin resistance. Often seen in obesity, diabetes. Rarely associated with malignancy.

Other Skin Tumors

• Pityriasis Alba: Common, benign, self-limiting skin condition characterized by hypopigmented, scaly patches primarily in children and adolescents. Often in the face (cheeks) and neck, arms, and trunk. Form of atopic dermatitis associated with xerosis (dry skin. Hypopigmented light colored patches. Initially pink or red, fading to pale white over time. Fine scaling. Round, oval irregular shape (0.5-2cm). Lesions persist weeks to months, gradual repigmentation. Associated with atopic dermatitis and xerosis. Increased transepidermal water loss, dryness, and mild inflammation.

Premalignant and Malignant Epidermal Tumors

• Actinic Keratosis: Premalignant skin lesions, caused by sun exposure. Growth of atypical epidermal keratinocytes; can lead to squamous cell carcinoma. Round, red/brown papules or plaques. Sun-exposed areas.

• Squamous Cell Carcinoma (SCC): 2nd most common skin cancer. Arises from squamous cells in the epidermis. Occurs in sun-exposed areas (face, lips, ears, hands). DNA damage by UV light. Common in older adults (>75). Less than 5% metastasize to regional nodes. Rarely metastasize beyond nodes. Red, scaling plaques with sharp borders. More advanced lesions: ulcerate, keratin production. May crust or bleed. Risk factors: Sun exposure. Chronic immunosuppression. Organ transplants, HIV, long-term glucocorticoids. Chronic skin inflammation. Burns, chronic ulcers, and draining sinus tracts. Arsenic exposure.

• Basal Cell Carcinoma (BCC): Most common skin cancer. Slow growing. Rarely metastasizes. Most are found early and excised. Occur in sun-exposed areas. Lowest potential for recurrence or metastases. Pearly papules or nodules. May have telangiectasia on surface.