AOBD Dermatology key terms

Pinpoint bleeding that appears when scale is lifted from a lesion, caused by dilated superficial dermal capillaries close to the surface. It is classically associated with psoriasis but can occur in other scale-topped conditions.

Separation of the upper epidermis when lateral pressure is applied to skin adjacent to a blister or erosion. A positive sign indicates loss of keratinocyte cohesion, as in pemphigus vulgaris or toxic epidermal necrolysis.

A wheal-and-flare response that develops within minutes after stroking or scratching the skin, reflecting mast cell degranulation. It is a form of physical urticaria and is usually benign and self-limited.

Development of new lesions of a skin disease along lines of trauma, scratching, or surgery in previously uninvolved skin. It is seen in psoriasis, lichen planus, vitiligo, and other conditions.

A severe mucocutaneous reaction, usually drug-induced, marked by widespread epidermal death and detachment of large sheets of skin. It is distinguished from Stevens-Johnson syndrome mainly by the percentage of body surface area involved.

Raised, itchy, transient wheals caused by dermal edema from mast cell mediator release. Individual lesions typically resolve within 24 hours, and angioedema may accompany them when deeper tissue is involved.

Regular elongation of rete ridges with thickening of the epidermis, producing a test-tube-like appearance on microscopy. It is the characteristic epidermal pattern of psoriasis and some spongiotic or lichenoid mimics.

Retention of nuclei within the stratum corneum, indicating incomplete or accelerated keratinization. It is a common finding in psoriasis, spongiotic dermatitis, and many other inflammatory skin diseases.

Intercellular edema between keratinocytes that widens the spaces between cells and stretches desmosomes, giving a sponge-like appearance. It is the hallmark epidermal change of eczematous dermatitis.

A band-like lymphocytic infiltrate hugging the dermoepidermal junction with damage to basal keratinocytes. It produces the clinical pattern seen in lichen planus and lichenoid drug eruptions.

Loss of cohesion between keratinocytes caused by breakdown of intercellular attachments, leading to rounded detached cells. It is the defining mechanism of blister formation in pemphigus and Hailey-Hailey disease.

Individually dying keratinocytes that appear as shrunken, eosinophilic bodies scattered through the epidermis. They are a feature of lichenoid reactions, graft-versus-host disease, and erythema multiforme.

A test in which fluorescent antibodies are applied to a patient's skin biopsy to detect bound immunoglobulins or complement. It is essential for diagnosing autoimmune blistering diseases such as pemphigus and bullous pemphigoid.

A technique in which a skin specimen is incubated in concentrated salt solution to separate the epidermis from the dermis at the basement membrane. Fluorescent antibody binding above or below the split helps distinguish pemphigus from pemphigoid.

Cytologic and architectural features of melanocytes that deviate from benign nevus cells, such as enlarged nuclei, irregular spacing, and poor maturation. Grading atypia helps distinguish dysplastic nevi from melanoma.

The measured depth of a melanoma from the granular layer of the epidermis to the deepest invasive tumor cell. It is the single most important prognostic factor and guides staging and surgical margins.

A staged surgical technique in which tumor is excised, mapped, and examined microscopically in horizontal sections while the patient waits. It maximizes tissue conservation and cure rates for skin cancers in high-risk locations.

Rapid tissue processing in which a specimen is frozen, cut, and stained for immediate microscopic review during surgery. It is used in Mohs surgery to confirm tumor clearance before reconstruction.

Removal of the bulk of a visible tumor before taking the thin, mapped layers examined by frozen section in Mohs surgery. It reduces the number of stages needed while preserving the margin assessment.

The most common skin cancer, arising from basal keratinocytes and typically appearing as a pearly papule with telangiectasias. It rarely metastasizes but can cause local tissue destruction if untreated.

A malignant tumor of keratinocytes, often on sun-exposed skin, that may arise from actinic keratosis and can metastasize. Risk factors include ultraviolet exposure, immunosuppression, and chronic wounds.

A rough, scaly lesion on sun-damaged skin representing intraepidermal keratinocyte dysplasia. It is considered a precursor to squamous cell carcinoma and is treated with cryotherapy, topical agents, or field therapy.

A chronic, relapsing inflammatory skin disease characterized by dry, intensely itchy skin and a course that often begins in infancy. It is driven by barrier dysfunction and immune dysregulation and is associated with asthma and allergic rhinitis.

Widespread herpes simplex virus infection superimposed on pre-existing skin disease, most often atopic dermatitis. It presents with punched-out monomorphic vesicles and erosions and is a medical emergency requiring systemic antiviral therapy.

A common, benign eruption in the first days of life consisting of blotchy erythema with small yellow-white pustules. It resolves spontaneously and requires no treatment.

A heat-related eruption caused by obstruction of eccrine sweat ducts, producing tiny papules or vesicles. Variants include miliaria crystallina and miliaria rubra, especially in infants in warm environments.

Small white spots on an erythematous buccal mucosa that appear shortly before the rash of measles. They are a classic early diagnostic sign of rubeola infection.

A red, swollen tongue with prominent papillae seen in Kawasaki disease and streptococcal scarlet fever. It reflects mucocutaneous inflammation and helps distinguish these febrile illnesses.

A benign vascular tumor that appears shortly after birth, grows rapidly for months, and then slowly involutes. Most require only observation, but some need treatment because of location, size, or ulceration.

A uniformly light-brown, flat patch present from birth or early childhood. Multiple lesions suggest neurofibromatosis type 1, particularly when combined with axillary freckling.

A chronic inflammatory condition causing greasy scale and erythema on the scalp, face, and intertriginous areas. It is linked to Malassezia yeast and is common in infants and adults.

A self-limited eruption that often begins with a single larger herald patch followed by oval scaly lesions along skin cleavage lines. It typically resolves within weeks to months and needs only symptomatic care.

The initial, larger, finely scaly oval lesion that precedes the generalized rash of pityriasis rosea. It usually appears on the trunk days to weeks before the smaller secondary lesions.

Noninvasive examination of skin lesions with a magnifying device that reveals subsurface colors and structures. It improves diagnostic accuracy for melanoma and other pigmented and vascular lesions.

Complete removal of a lesion with a margin of normal tissue for histologic examination. It is preferred for suspected melanoma so the entire lesion can be assessed for depth and margins.

A cylindrical full-thickness sample of skin taken with a round cutting instrument. It is useful for inflammatory dermatoses and small lesions but does not fully sample large tumors.

An ultraviolet light source used to examine skin fluorescence and pigment changes. It helps detect conditions such as vitiligo, tinea capitis, and some pigmentary disorders.

An acquired disorder of depigmented macules caused by loss of functioning melanocytes. Lesions are well demarcated and may be associated with autoimmune thyroid disease and other conditions.