The truism that ‘there is no substitute for a good history’ is just as applicable in dermatology as in any other branch of medicine. Indeed, history-taking is a core skill in the medical curriculum. The time needed to take a history depends on the complaint. For example, the history in a patient with hand warts can usually be completed quickly, but more time and detailed questioning…
Dermatology has a vocabulary that is quite distinct from that of other medical specialties and without which it is impossible to describe skin disorders (a skill vital in dermatologist training curricula). A lesion is a general term for an area of disease, usually small. An eruption ( or rash) is a more widespread skin involvement, normally composed of several lesions, which may be the primary pathology…
Recent and rapid advances in genetics have had an impact on our understanding of skin diseases. The Human Genome Project has now mapped all human genes, of which there are about 35 000. Whilst the original Mendelian concept of single gene (monogenic) disorders applies to many skin diseases, which can therefore show classical patterns of inheritance including autosomal dominant (AD), and autosomal recessive (AR). These conditions…
Inflammatory responses are central to biological homeostasis. Inflammation is mediated by molecular signalling between resident skin cells and specialized immunological cells which results in specific cellular interactions, or by release of soluble mediators. In the skin, strong inflammatory reactions are important for defence against infection (e.g. redness and exudate in impetigo), but in immunocompromised individuals, the risk of infection is increased (e.g. viral warts). As well…
Keratins The important molecules synthesized by the skin include keratin, melanin, collagen and glycosaminoglycans (GAGs). Keratins are high-molecular-weight polypeptide chains produced by keratinocytes ( Fig. 4.1 ). They are the major constituents of the stratum corneum, hair and nails. The stratum corneum comprises 65% keratin (along with 10% soluble protein, 10% amino acid, 10% lipid and 5% cell membrane). Keratin proteins are of varying molecular weight…
The skin is a metabolically active organ with vital functions ( Box 3.1 ), including the protection and homeostasis of the body. Box 3.1 Functions of skin Presents barrier to physical agents Protects against mechanical injury Antimicrobial peptides have a bactericidal effect Prevents loss of body fluids Reduces penetration of UV radiation Helps to regulate body temperature Acts as a sensory organ Affords a surface for…
Hair Hairs are found over the entire surface of the skin, with the exception of the glabrous skin of the palms, soles, glans penis and vulval introitus. The density of follicles is greatest on the face. Embryologically, the hair follicle has an input from the epidermis, which is responsible for the matrix cells and the hair shaft, and the dermis, which contributes to the papilla, with…
Key features ▪ The skin is one of the most common targets for adverse drug reactions ▪ To determine the cause of the eruption, a logical approach based on clinical characteristics, chronologic factors, and a literature search is required ▪ Exanthematous eruptions and urticaria are the two most common forms of cutaneous drug reactions ▪ When an exanthematous eruption is associated with fever, lymphadenopathy, and/or edema…
Introduction The skin is one of the largest organs in the body, having a surface area of 1.8 m 2 and making up about 16% of body weight. It has many functions, the most important of which is as a barrier to protect the body from noxious external factors and to keep the internal systems intact. Skin is composed of three layers: the epidermis, the dermis…
Erythema Multiforme Synonym ▪ Erythema multiforme minor – erythema multiforme von Hebra Key features ▪ A self-limited but potentially recurrent disease ▪ Abrupt onset of papular “target” lesions, with the vast majority of lesions appearing within 24 hours ▪ Two types of target lesions are recognized: (1) typical, with at least three different zones; and (2) atypical papular, with only two different zones and/or a poorly…
Introduction Erythema represents a change in the color of the skin that is due to the dilation of blood vessels, especially those in the papillary and reticular dermis. The color, which is blanchable, can vary from pink to dark red to violaceous. Most erythemas last for days to months, but some may last only minutes (e.g. flushing). A very heterogeneous group of cutaneous disorders manifests as…
Synonyms ▪ Wheals – hives, nettle rash ▪ Angioedema – Quincke edema, angioneurotic edema Key features ▪ Urticaria is characterized by transient skin or mucosal swellings due to plasma leakage. Superficial dermal swellings are wheals, and deep swellings of the skin or mucosa are termed angioedema. Wheals are characteristically pruritic and pink or pale in the center, whereas angioedema is often painful, less well-defined, and shows…
Key features ▪ Plant constituents produce a variety of adverse cutaneous reactions, including a significant proportion of cases of allergic contact dermatitis ▪ Adverse cutaneous reactions are due to a small minority of plants ▪ The most common dermatoses related to plants are: urticaria, mechanical and chemical irritant contact dermatitis, phytophotodermatitis, and allergic contact dermatitis ▪ Two major plant allergens are urushiol (Anacardiaceae family which includes…
Introduction Given the diverse occupations that people pursue, there are thousands of chemicals and other potentially noxious insults that can impinge on the skin in many different ways . Traditionally, the types of hazardous exposure are categorized as: mechanical – friction, pressure, vibration, mechanical disruption chemical – elements and chemical compounds (organic, inorganic, and proteins) physical – heat, cold, radiation (UV and ionizing) biological – organisms…
Synonyms ▪ Irritant reaction ▪ Irritant dermatitis ▪ Irritant dermatitis syndrome ▪ Irritant contact dermatitis syndrome ▪ Toxic contact dermatitis ▪ “Housewife's eczema” ▪ “Chemical burn” Key features ▪ Irritant contact dermatitis (ICD) is a localized, non-immunologically initiated, cutaneous inflammatory reaction. Its clinical characteristics are polymorphous, and they include erythema, scaling, edema, vesiculation, and erosions in acute cases, with erythema, lichenification, hyperkeratosis, and fissures in chronic…
Synonyms ■ Contact dermatitis ■ Contact eczema Key features ■ Allergic contact dermatitis (ACD) is a pruritic, eczematous reaction ■ Acute ACD and many cases of chronic ACD are well demarcated and localized to the site of contact with the allergen ■ ACD can also have a diffuse or patchy distribution, depending on the allergen and/or the development of disseminated eczema (autosensitization dermatitis) ■ The prototypic…
In addition to contact and atopic dermatitis, there exists a heterogeneous group of inflammatory skin diseases that obviously share the hallmarks of eczema, but display characteristic additional features. Their pathogenesis is generally less well understood, but most exhibit distinctive etiologic features. Seborrheic Dermatitis Key features ▪ Infantile and adult forms ▪ Lesions favor the scalp, ears, face, central chest, and intertriginous areas ▪ Etiologic links with…
Synonym ▪ Atopic eczema Key features ▪ Common inflammatory skin condition that typically begins during infancy or early childhood and is often associated with other atopic disorders such as asthma, allergic rhinoconjunctivitis, food allergies, and eosinophilic esophagitis ▪ Complex genetic disease with environmental influences ▪ Characterized by intense pruritus and a chronic or chronically relapsing course ▪ Acute inflammation and involvement of the cheeks, scalp and…
Lichen Planus Synonym ▪ Lichen ruber planus Key features ▪ Idiopathic inflammatory disease of the skin, hair, nails and mucous membranes, seen most commonly in middle-aged adults ▪ Flat-topped violaceous papules and plaques favoring the wrists, forearms, genitalia, distal lower extremities, and presacral area ▪ Clinical variants include actinic, annular, atrophic, bullous, hypertrophic, inverse, linear, ulcerative, vulvovaginal–gingival, lichen planopilaris, lichen planus pigmentosus, and drug-induced ▪ Some…
Synonyms ▪ Exfoliative dermatitis ▪ Exfoliative erythroderma ▪ Red man syndrome Key features ▪ Erythroderma is clinically defined as erythema and scaling involving >80–90% of the body surface area ▪ Systemic manifestations include peripheral edema, tachycardia, loss of fluid and proteins, and disturbances in thermoregulation ▪ Erythroderma has multiple etiologies; the most common causes are psoriasis, drug reactions, atopic dermatitis, and cutaneous T-cell lymphoma (CTCL) ▪…