Dermatology Cheat Sheet

The core ideas of Dermatology distilled into a single, scannable reference — perfect for review or quick lookup.

PiqCue — piqcue.com/dermatology/cheatsheet

Quick Reference

Skin Barrier Function

The stratum corneum and associated lipids form a selectively permeable barrier that prevents transepidermal water loss, blocks pathogen entry, and protects against environmental insults. Disruption of this barrier is central to conditions such as atopic dermatitis and irritant contact dermatitis.

Morphology of Skin Lesions

The systematic description of skin lesions by their primary morphology (macule, papule, plaque, vesicle, bulla, nodule, pustule, wheal) and secondary changes (scale, crust, erosion, ulcer, lichenification) is the foundation of dermatologic diagnosis.

Dermatopathology

The subspecialty that examines skin biopsy specimens under the microscope to establish histologic diagnoses. It correlates clinical findings with microscopic patterns such as spongiosis, acanthosis, interface dermatitis, and granulomatous inflammation.

Psoriasis Pathophysiology

Psoriasis is a chronic, immune-mediated inflammatory disease driven primarily by the IL-23/Th17 axis. Dysregulated T-cells release cytokines such as IL-17 and TNF-alpha, causing keratinocyte hyperproliferation and the characteristic plaques.

Melanoma and the ABCDEs

Melanoma is the most lethal form of skin cancer, arising from melanocytes. The ABCDE criteria (Asymmetry, Border irregularity, Color variation, Diameter greater than 6 mm, and Evolution) are clinical screening tools for early detection.

Atopic Dermatitis

A chronic, relapsing inflammatory skin disease characterized by intense pruritus and eczematous lesions. It involves a complex interplay of genetic predisposition, epidermal barrier dysfunction, immune dysregulation (Th2 predominance), and environmental triggers.

Contact Dermatitis

An inflammatory skin reaction caused by direct contact with an irritant (irritant contact dermatitis) or an allergen (allergic contact dermatitis). Allergic contact dermatitis is a type IV delayed hypersensitivity reaction mediated by T-cells.

Mohs Micrographic Surgery

A precise surgical technique for removing skin cancer in which thin layers of tissue are excised and examined microscopically in real time until clear margins are achieved. It offers the highest cure rate while sparing maximum healthy tissue.

Acne Vulgaris Pathogenesis

Acne results from four interrelated factors: excess sebum production, follicular hyperkeratinization, colonization by Cutibacterium acnes, and inflammation. Hormonal influences, particularly androgens, drive sebum production during puberty.

Skin Cancer Spectrum

Skin cancers range from basal cell carcinoma (most common, locally invasive, rarely metastasizes) to squamous cell carcinoma (can metastasize, especially in immunosuppressed patients) to melanoma (least common but most deadly). UV radiation is the primary modifiable risk factor for all three.

Key Terms at a Glance

Acanthosis:Thickening of the stratum spinosum (prickle cell layer) of the epidermis.

Actinic Keratosis:A precancerous, rough, scaly patch on sun-damaged skin caused by chronic UV exposure; may progress to squamous cell carcinoma.

Biopsy:The removal of a tissue sample for histologic examination. Common dermatologic types include shave, punch, and excisional biopsies.

Comedo:A plugged pilosebaceous follicle. Open comedones (blackheads) have a dilated pore; closed comedones (whiteheads) are covered by skin.

Corticosteroid (Topical):An anti-inflammatory medication applied to the skin, classified by potency from class I (superpotent) to class VII (least potent).

Cryotherapy:The use of extreme cold (typically liquid nitrogen) to destroy abnormal tissue such as warts, actinic keratoses, and superficial skin cancers.

Dermis:The layer of skin beneath the epidermis containing collagen, elastin, blood vessels, nerves, hair follicles, and sweat glands.

Dermoscopy:A non-invasive technique using a handheld device with magnification and polarized light to examine pigmented and non-pigmented skin lesions.

Eczema:A general term for inflammatory skin conditions characterized by itching, redness, and vesiculation. Atopic dermatitis is the most common form.

Epidermis:The outermost layer of the skin composed mainly of keratinocytes arranged in stratified layers from stratum basale to stratum corneum.

Erythema:Redness of the skin caused by dilation of superficial blood vessels, often a sign of inflammation or infection.

Excoriation:A secondary skin lesion caused by scratching, resulting in a loss of the epidermis and upper dermis.

Hives (Urticaria):Raised, itchy wheals caused by mast cell degranulation and histamine release; individual lesions typically resolve within 24 hours.

Hyperpigmentation:Darkening of the skin due to excess melanin production, which may follow inflammation, sun exposure, or hormonal changes.

Immunofluorescence:A laboratory technique using fluorescent-labeled antibodies to detect immune deposits (IgG, IgA, complement) in skin biopsy specimens. Critical for diagnosing autoimmune blistering diseases.

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