#dermatology

• Abstergent — A substance, solution, or pharmaceutical preparation capable of cleansing biological tissues, wounds, or ulcerations by dissolving and removing dead cells, secretions, and impurities; (as an adjective) possessing purifying, detersive, and healing properties on the skin or mucous membranes.
• Acantholysis — A histological pathological process characterized by the loss of intercellular cohesion between keratinocytes in the stratum spinosum of the epidermis, caused by the destruction or dysfunction of desmosomes (cellular junction structures). This biochemical and immunological phenomenon leads to the separation of epithelial cells, formation of clefts, and subsequent development of intraepidermal vesicles or bullae, serving as the definitive microscopic hallmark for severe autoimmune diseases such as pemphigus vulgaris.
• Acanthoma — A benign cutaneous tumor formation characterized by the hyperplastic proliferation of keratinocytes within the stratum spinosum of the epidermis (acanthosis). This well-circumscribed lesion can manifest in various clinical and histological forms, the most notable being clear cell acanthoma (Degos) and acanthoma fissuratum, requiring microscopic differential diagnosis to exclude epidermal malignancies.
• Acanthosis — A histopathological alteration consisting of the thickening of the prickle cell layer (stratum spinosum) of the epidermis, caused by the proliferation of malpighian cells. In a clinical macroscopic sense, the term is frequently associated with 'Acanthosis nigricans', a skin condition characterized by hyperpigmented, velvety, and rough plaques, predominantly localized in intertriginous areas (neck, axillae, groin), serving as an important cutaneous marker for insulin resistance, obesity, or endocrine disorders.
• Acariasis — A generic term designating any contagious, parasitic skin, respiratory, or systemic disease caused by infestation with various species of mites in humans and animals. In human medicine, the most prominent manifestation is sarcoptic acariasis (scabies), whereas in apiculture and animal husbandry, the term describes severe conditions such as acarine disease of honeybees (caused by Acarapis woodi in the tracheae) or various forms of demodectic and psoroptic mange.
• Acrodermatitis — An inflammatory, chronic, or acute dermatological disorder localized exclusively or predominantly on the extremities of the body (hands, feet, fingers), manifesting as cutaneous lesions, erythema, or vesicles.
• Acroerythrosis — A peripheral circulatory disorder characterized by a persistent, intense, and often symmetrical reddish or purplish discoloration of the extremities (hands, feet, digits), caused by capillary dilation.
• Acrogeria — A rare congenital structural disorder characterized by premature aging, severe atrophy, and loss of subcutaneous adipose tissue localized exclusively within the extremities (hands and feet), also known as Gottron's syndrome.
• Achromatosis — A generalized pathological condition characterized by the total absence or severe diminution of normal pigmentation within a tissue, organ, or the entire organism. In dermatology, the term describes severe states of cutaneous depigmentation (such as extreme forms of albinism or vitiligo universalis) where cells no longer produce melanin.
• Achromia — The total congenital or acquired absence of normal pigmentation of the skin, hair, or other tissues, caused by the lack or destruction of melanocytes and melanin production. This general medical term covers manifestations such as generalized albinism or completely white patches occurring in advanced vitiligo.
• Leukoderma — A congenital or acquired cutaneous pathological condition characterized by the total absence or severe and extensive diminution of normal skin pigmentation, manifesting as broad white patches or generalized depigmentation of the epidermis. This structural disorder is caused by the absence, destruction, or chronic metabolic dysfunction of melanocytes, leading to a complete halt in melanin production and resulting in extreme skin sensitivity to ultraviolet radiation.
• Achromotrichia — A pathological condition or biological phenomenon characterized by the total loss or congenital absence of natural pigment within the hair shaft structure, leading to complete whitening or discoloration. This structural dermatological process is caused by the cessation of melanin production by the melanocytes within the hair follicle, and can be triggered by hereditary factors, severe nutritional deficiencies (such as a lack of copper or pantothenic acid), intense oxidative stress, or autoimmune disorders.
• Acropachydermia — A rare pathological clinical condition, congenital or acquired, characterized by the symmetric hypertrophic thickening of the skin and soft tissues of the extremities (hands and feet), often associated with subperiosteal osteoarticular deformities of the phalanges. This severe structural phenomenon impairs cutaneous elasticity and fine joint mobility, frequently manifesting within complex neuroendocrine syndromes, such as pachydermoperiostosis (Touraine-Solente-Golé syndrome), or as a secondary paraneoplastic reaction in chronic pulmonary diseases.
• Acroscleroderma — A localized clinical form or initial stage of systemic sclerosis (scleroderma), characterized by the thickening, induration, and progressive loss of skin elasticity restricted to the distal extremities (hands, feet) and the face. This structural autoimmune process alters microcirculation and dermal connective tissue, being almost constantly associated with Raynaud's phenomenon, painful digital tip ulcers, sclerodactyly, and facial tightening.
• Actinopathy — A structural medical term used to define any pathological state, skin lesion, or systemic condition directly caused by prolonged, accidental, or therapeutic exposure to light radiation, ultraviolet rays, or ionizing radiation (X-rays and gamma rays). Actinopathy encompasses conditions ranging from acute radiodermatitis and severe sunburns to deep cellular degenerative changes or actinic cataracts induced by aggressive radiant fluxes.
• Adiaphoresis — A pathological condition characterized by the total absence or severe diminution, congenital or acquired, of sweat secretion (perspiration). This structural clinical phenomenon disrupts the body's normal thermoregulation, exposing the patient to major risks of overheating (hyperthermia) and heatstroke in high ambient temperatures.
• Allergid — A secondary cutaneous eruption, of an allergic or inflammatory nature, appearing on the skin as a distant immune response to a primary infectious focus (bacterial, fungal, or parasitic) in the body, without the original pathogen being present in the secondary dermatological lesions. Structurally, allergids (such as mycids or tuberculids) reflect a cell-mediated dermo-epidermal hypersensitivity reaction.
• Ointment — Unarticulated form; a medicine or cosmetic product of soft and greasy consistency, obtained by mixing active ingredients with animal, vegetable, or synthetic fats. It is used for rubbing or greasing the skin to heal wounds, soothe irritations, provide dermatological protection, or nourish the external layers of the epidermis.
• Alopecic — Pertaining to alopecia or characterized by partial or total hair loss; presenting areas devoid of hair (baldness, calvities) due to pathological, genetic, or autoimmune causes. In structural clinical dermatology, the term describes a lesion or tegumentary region atrophied or affected by the loss of hair follicles, requiring dermoscopic investigations.
• Alopecia — The partial or total loss of hair from the scalp or other regions of the body, caused by genetic factors, endocrine imbalances, autoimmune diseases, systemic stress, or aggressive medical treatments. This structural pathological phenomenon affects the natural growth cycle of hair follicles, leading to their miniaturization or destruction, and is classified into cicatricial (irreversible) and non-cicatricial forms.