Arab Board Dermatology Final key terms

The appearance of new skin lesions along a line of trauma in a person with existing skin disease, classically seen in psoriasis, lichen planus and vitiligo. It reflects an abnormal response to injury rather than infection.

Pinpoint bleeding that appears when the scale is removed from a psoriatic plaque, caused by exposure of elongated, dilated dermal papillary capillaries. It is a clinical clue supporting psoriasis over other scaly plaques.

A chronic immune-mediated inflammatory disease driven by IL-23/Th17 pathways, producing well-demarcated erythematous plaques with silvery scale on extensor sites. It may involve joints and carries metabolic and cardiovascular comorbidity.

An idiopathic T-cell-mediated interface dermatitis producing pruritic, purple, polygonal, planar papules and plaques, often with fine white lines on the surface. Mucosal, scalp and nail involvement may occur.

Delicate white lacy lines on the surface of lichen planus lesions, especially on mucosal surfaces, corresponding to focal hypergranulosis. They help distinguish lichen planus from other violaceous papular eruptions.

Intercellular edema between keratinocytes of the epidermis that widens the spaces and stretches desmosomes, giving a spongy appearance. It is the histological hallmark of eczematous dermatitis and explains vesicle formation.

A chronic relapsing pruritic eczematous disease arising from skin barrier dysfunction, often with filaggrin mutations, and skewed type 2 immune responses. It usually begins in childhood and is associated with asthma and allergic rhinitis.

A structural protein that aggregates keratin filaments and is degraded into natural moisturizing factors in the stratum corneum. Loss-of-function mutations impair the skin barrier and predispose to atopic dermatitis and ichthyosis vulgaris.

A diagnostic procedure in which suspected allergens are applied to the back under occlusion and read at delayed intervals to detect type IV cell-mediated hypersensitivity. It is the gold standard for allergic contact dermatitis.

An eczematous eruption at sites of skin contact with an allergen, mediated by hapten-specific T lymphocytes after prior sensitization. It is delayed in onset and often sharply demarcated by the exposure pattern.

Separation of the upper epidermis with lateral pressure, indicating loss of keratinocyte cohesion. A positive sign suggests pemphigus vulgaris or toxic epidermal necrolysis, whereas it is negative in bullous pemphigoid.

An autoimmune blistering disease in which IgG antibodies target desmoglein 3, causing suprabasal acantholysis and flaccid blisters with erosions of skin and mucosa. Direct immunofluorescence shows intercellular epidermal IgG.

A transmembrane cadherin family protein forming desmosomal attachments between keratinocytes. Autoantibodies against desmoglein 1 and 3 underlie pemphigus foliaceus and vulgaris respectively.

Loss of intercellular adhesion between keratinocytes so that cells separate and round up, leaving clefts within the epidermis. It is the defining histologic event in pemphigus and is also seen in Hailey-Hailey disease.

A technique using fluorochrome-labeled antibodies on a patient's fresh skin biopsy to detect in vivo deposition of immunoglobulins or complement. The pattern and site of deposition help classify autoimmune blistering diseases and lupus.

Detection of a continuous granular band of IgG and complement at the dermoepidermal junction of lesional or sun-exposed skin by direct immunofluorescence. It supports a diagnosis of systemic lupus erythematosus but is not entirely specific.

A multisystem autoimmune disease with autoantibodies against nuclear antigens, producing photosensitive rashes, arthritis, cytopenias and renal disease. Skin findings include malar rash, discoid lesions and mucosal ulcers.

An idiopathic inflammatory myopathy with characteristic skin signs such as violaceous periorbital erythema, Gottron papules and photosensitive poikiloderma, plus proximal muscle weakness. It carries an increased risk of internal malignancy in adults.

Violaceous to erythematous scaly papules over the knuckles and other bony prominences, a pathognomonic cutaneous sign of dermatomyositis. They are often accompanied by nail fold capillary changes.

Localized scleroderma producing indurated, bound-down plaques of skin with a violaceous inflammatory border in active phases. Unlike systemic sclerosis, it usually spares the digits and lacks Raynaud phenomenon and internal organ fibrosis.

A connective tissue disease with microvascular injury and excessive collagen deposition, causing skin thickening, Raynaud phenomenon, digital ulcers and internal organ fibrosis. Antinuclear antibody patterns and specific autoantibodies aid classification.

Episodic reversible vasospasm of digital arteries triggered by cold or stress, producing blanching, cyanosis and rubor of the fingers. It may be primary or secondary to connective tissue disease such as systemic sclerosis.

In vivo magnification of skin structures using polarized or non-polarized light to reveal pigment networks, vascular patterns and other features invisible to the naked eye. It improves diagnostic accuracy for melanoma and other pigmented and vascular lesions.

The measured depth of a melanoma from the granular layer of the epidermis to its deepest invasive point, expressed in millimeters. It is the strongest single prognostic factor and guides staging and surgical margins.

A malignant neoplasm of melanocytes that may arise de novo or from a nevus, presenting as an asymmetric, irregularly bordered, multicolored lesion. Prognosis depends chiefly on Breslow thickness, ulceration and nodal status.

Identification and removal of the first draining lymph node from a tumor bed using dye or radiotracer mapping to detect occult metastasis. It is used for staging in melanoma and some squamous cell carcinomas.

A locally destructive but rarely metastasizing keratinocyte tumor with pearly translucent papules, telangiectasia and a rolled border, often on sun-exposed skin. Histology shows basaloid islands with peripheral palisading and clefting.

A tissue-sparing technique in which the tumor is excised and the entire peripheral and deep margin is examined microscopically on frozen sections during the same session. It offers high cure rates for tumors with ill-defined or high-risk features.

A malignant tumor of keratinocytes, usually arising in sun-damaged skin or from actinic keratosis, presenting as a firm hyperkeratotic or ulcerated nodule. Risk of metastasis is higher with deep invasion, immunosuppression and certain anatomic sites.

A rough, scaly macule or papule on chronically sun-exposed skin representing intraepidermal dysplasia of keratinocytes. It is a precursor lesion for squamous cell carcinoma and is treated with cryotherapy or field-directed therapies.

An autosomal dominant disorder caused by PTCH1 mutations, featuring multiple basal cell carcinomas, palmoplantar pits, jaw keratocysts and skeletal anomalies. Patients require lifelong photoprotection and surveillance.

An autosomal dominant scaling disorder from filaggrin loss of function, producing fine polygonal scales on extensor surfaces and sparing of flexures. It often coexists with atopic dermatitis and improves in humid weather.

A group of inherited disorders with mutations in structural proteins of the skin, causing blisters after minor mechanical trauma. Subtypes are classified by the level of cleavage within or below the basement membrane.

An intensely pruritic infestation by the mite Sarcoptes scabiei, with burrows, papules and nocturnal itching, often involving finger webs and genitalia. Diagnosis is confirmed by microscopy of skin scrapings or dermoscopy.

Cytologic examination of material scraped from the base of a vesicle and stained to look for multinucleated giant cells or acantholytic cells. It gives rapid but nonspecific support for herpesvirus infection or pemphigus.

A severe drug-triggered mucocutaneous reaction with widespread epidermal detachment and a positive Nikolsky sign, usually involving more than thirty percent of body surface area. It is a dermatologic emergency requiring intensive supportive care.

A severe mucocutaneous hypersensitivity reaction, usually to drugs, with epidermal detachment of less than ten percent of body surface area plus prominent mucosal erosions. It lies on a spectrum with toxic epidermal necrolysis.

A rapidly developing systemic hypersensitivity reaction with airway compromise, bronchospasm and hypotension, treated immediately with intramuscular epinephrine. Skin signs such as urticaria may be absent in severe cases.

Pruritic, transient wheals from mast cell histamine release causing dermal edema, with individual lesions lasting under twenty-four hours. Chronic spontaneous forms are investigated for triggers and autoimmune causes.

A treatment applying a photosensitizer such as aminolevulinic acid to the skin followed by light activation, generating reactive oxygen species that destroy dysplastic cells. It is used for actinic keratoses and superficial skin cancers.

Treatment with engineered antibodies or fusion proteins that block specific immune pathways, such as TNF, IL-17, IL-23 or IL-4/13. These agents require screening for latent tuberculosis and hepatitis before initiation.

A monoclonal antibody blocking the shared alpha subunit of the IL-4 and IL-13 receptors, used for moderate-to-severe atopic dermatitis and related type 2 diseases. It is generally well tolerated but may cause conjunctivitis.