Text Book of Dermatology EDITOR-N-CHIEF Xu jinhua Department of dermatology Huashan Hospita Fudan University
Text Book of Dermatology EDITOR-IN-CHIEF Xu Jinhua Department of Dermatology Huashan Hospital Fudan University
CONTENTS hapterl Structure and function of human skin Chapter 2 Diagnosis of skin Disease Chapter 3 Therapy in Dermatology and venereology Chapter4 Fungal Diseases Chapter 5 Common viral diseases of skin Chapter 7 Sexually transmitted diseases Chapter 8 Contact Dermatitis Chapter 9 Neurodermatitis Chapter 10 ecz Chapter ll Urticaria Chapter 12 drug eruption Chapter 13 Papulosquamous dermatoses Chapter 14 Lupus Erythematosus Chapter 15 Bullous Dermatoses Chapter 16 vitiligo Chapter 17 Acne
CONTENTS Chapter1 Structure and function of human skin Chapter 2 Diagnosis of Skin Disease Chapter 3 Therapy in Dermatology and Venereology Chapter 4 Fungal Diseases Chapter 5 Common viral diseases of skin Chapter 6 Scabies Chapter 7 Sexually Transmitted Diseases Chapter 8 Contact Dermatitis Chapter 9 Neurodermatitis Chapter 10 Eczema Chapter 11 Urticaria Chapter 12 Drug Eruption Chapter 13 Papulosquamous dermatoses Chapter 14 Lupus Erythematosus Chapter 15 Bullous Dermatoses Chapter 16 Vitiligo Chapter 17 Acne
Chapter 1 Structure and function of human skin Introduction of skin structure Human skin is a uniquely engineered organ covering the body Being the largest organ, the skin provides around 16% of the body mass of an average person, and it covers average area of 1.5 m2. The average thickness is 0. 5-4 mm (not includ ing subcutaneous fat tissue). The skin is thickest on the palms and soles. It is very thin on the eyelid performs many vital roles as both a barrier and a regulating influence between the outside world and the controlled environment within our bodies Skin color differs by race, age, gender and location. It is darker around external enitalia, anus, and areola The skin is composed of epidermis, dermis, subcutaneous tissue and skin appendag including hair follicles, sebaceous glands, ecrrine glands and apocrine glands, nmailsges on its surface by continuously alternating ridges and sulci, in individually unique roved There is no hair on the palms and soles, so called glabrous skin. Glabrous skin is configurations known as dermatoglyphics. It is characterized by the presence of glands. Hair-bearing skin, on the other hand, has both hair follicles and sebaceous gland h encapsulated sense organs within the dermis, and by a lack of hair follicles and sebaceou but lacks encapsulated sense organs Histology of the skin lEpidermis The epidermis is the outmost tissue in human beings. Derived from ectoderm, it can be classified as stratified squamous epithelium. Keratinocyte is the major cell, making up 95% of the total. Other cells include melanocytes, Langerhans cells and merkel cells D)Keratinocyte es move progressively from attachment to the epidermal basement membrane towards the skin surface, forming several well-defined layers. The differentiation process is called cornification The epidermis contains five histologically distinct layers from the inside to the outside stratum basale, stratum spinosum, stratum granulosum, stratum lucidum and stratum corneum a.The stratum basale(basal cell layer) is a continuous layer that is generally described as only one cell thick, but may be two to three cells thick in glabrous skin and hyperproliferative epidermis. The cells of the basal layer are similar to those of other tissues within the body they contain the typical organelles such as mitochondria and ribosomes, and the cells are metabolically active. The keratinocytes of the stratum basale are attached to the basement membrane by hemidesmosomes, which act rather like proteinaceous anchors for these lowest layer cells. Within the stratum basale and the adjacent cell layer, the stratum spinosum, keratinocytes are connected througl desmosomes, again highly specialised proteinaceous cellular bridges b The stratum spinosum(also known as the spinous layer or prickle cell layer) is found on top of the basal layer, and together these two layers are termed the Malpighian layer This spinous layer consists of two to six rows of keratinocytes that change morphology from columnar to polygonal cells. Within this layer the keratinocytes begin to differentiate and synthesise keratins that aggregate to form tonofilaments
Chapter 1 Structure and function of human skin Introduction of skin structure Human skin is a uniquely engineered organ covering the body. Being the largest organ, the skin provides around 16% of the body mass of an average person, and it covers an average area of 1.5 m2 . The average thickness is 0.5-4 mm (not including subcutaneous fat tissue). The skin is thickest on the palms and soles. It is very thin on the eyelid. It performs many vital roles as both a barrier and a regulating influence between the outside world and the controlled environment within our bodies. Skin color differs by race, age, gender and location. It is darker around external genitalia, anus, and areola. The skin is composed of epidermis, dermis, subcutaneous tissue and skin appendages including hair follicles, sebaceous glands, ecrrine glands and apocrine glands, nails. There is no hair on the palms and soles, so called glabrous skin. Glabrous skin is grooved on its surface by continuously alternating ridges and sulci, in individually unique configurations known as dermatoglyphics. It is characterized by the presence of encapsulated sense organs within the dermis, and by a lack of hair follicles and sebaceous glands. Hair-bearing skin, on the other hand, has both hair follicles and sebaceous glands but lacks encapsulated sense organs. Histology of the skin 1.Epidermis The epidermis is the outmost tissue in human beings. Derived from ectoderm, it can be classified as stratified squamous epithelium. Keratinocyte is the major cell, making up 95% of the total. Other cells include melanocytes, Langerhan’s cells and Merkel cells. 1) Keratinocyte Keratinocytes move progressively from attachment to the epidermal basement membrane towards the skin surface, forming several well-defined layers. The differentiation process is called cornification. The epidermis contains five histologically distinct layers from the inside to the outside: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum and stratum corneum: a.The stratum basale (basal cell layer) is a continuous layer that is generally described as only one cell thick, but may be two to three cells thick in glabrous skin and hyperproliferative epidermis. The cells of the basal layer are similar to those of other tissues within the body; they contain the typical organelles such as mitochondria and ribosomes, and the cells are metabolically active. The keratinocytes of the stratum basale are attached to the basement membrane by hemidesmosomes, which act rather like proteinaceous anchors for these lowest layer cells. Within the stratum basale and the adjacent cell layer, the stratum spinosum, keratinocytes are connected through desmosomes, again highly specialised proteinaceous cellular bridges. b.The stratum spinosum (also known as the spinous layer or prickle cell layer) is found on top of the basal layer, and together these two layers are termed the Malpighian layer. This spinous layer consists of two to six rows of keratinocytes that change morphology from columnar to polygonal cells. Within this layer the keratinocytes begin to differentiate and synthesise keratins that aggregate to form tonofilaments
C The stratum granulosum(or granular layer)is only one to three cell layers thick, the stratum granulosum contains enzymes that begin degradation of the viable cell components such as the nuclei and organelles. The granular cells are so called because they acquire granular structures. Keratohyalin granules mature the keratins within the d The stratum lucidum is the layer in which the cell nucleus disintegrates. There is an increase in keratinisation of the cells concomitant with further morphological changes such as cell flattening. The stratum lucidum can be found in soles and palms e The stratum corneum(or horny layer )is the final product of epidermal cell differentiation. Typically, the stratum corneum comprises only 10 to 15 cell layers and is around 10 um thick when dry. This thin layer consists of dead, anucleate, keratinised cells embedded in a lipid matrix. The stratum corneum serves to regulate water loss from the body whilst preventing the entry of harmful materials, includ ing microorganisms Typically, it takes 14 days for a cell from the stratum basale to differentiate into a stratum corneum cell, and the stratum corneum cells are typically retained for a further 14 days prior to shedding 2)Melanocyte The melanocyte is a dendritic, pigment-synthesizing cell derived from neural crest that is confined mainly to the basal layer. Differentiation of the melanocyte correlates with the acquisition of its primary functions: melanogenesis, arborization, and transfer of pigment to keratinocytes. There are important organizational relationships and functional interactions between keratinocytes and melanocytes that the melanocyte depends on for differentiation and function. Approximately 36 basal and suprabasal keratinocytes ar thought to coexist functionally with each melanocyte in an epidermal melanin unit 3) The langerhan’scll Langerhans cells are bone marrow-derived, antigen-processing and-presenting cells that are involved in a variety of T cell responses. Langerhans cells are dendritic and do not form junctions with any of the cells. They are distributed in the basal, spinous, and granular layers, showing a preference for a suprabasal position Langerhans cells migrate from the bone marrow to the circulation into the en s ife ly in embryonic development and continue to repopulate the epidermis throug a number of the markers expressed by the Langerhans cell are characteristic for other cells of the monocyte-macrophage lineage and provide some insight into their function Langerhans cells are the primary cells in the epidermis responsible for the recognition uptake, processing, and presentation of soluble antigen and haptens to sensitized T lymphocytes, and are implicated in the pathologic mechanisms underlying cutaneous immunological disorders pidermal appendage Pilosebaceous units, eccrine and apocrine glands and nails constitute epidermal appendages. Embryologically, they are ectodermal in origin I) Hair follicle Hair can be found in varying densities of growth over the entire surface of the bod ceptions being on the palms, soles and glans penis. Follicles are most dense on the scalp and face Each hair follicle is lined by germinative cells, which produce keratin; and by melanocytes, which synthesize pigment. The hair shaft consists of an outer cuticle, a
c.The stratum granulosum (or granular layer) is only one to three cell layers thick, the stratum granulosum contains enzymes that begin degradation of the viable cell components such as the nuclei and organelles. The granular cells are so called because they acquire granular structures. Keratohyalin granules mature the keratins within the cell. d.The stratum lucidum is the layer in which the cell nucleus disintegrates. There is an increase in keratinisation of the cells concomitant with further morphological changes such as cell flattening. The stratum lucidum can be found in soles and palms. e.The stratum corneum (or horny layer ) is the final product of epidermal cell differentiation. Typically, the stratum corneum comprises only 10 to 15 cell layers and is around 10 µm thick when dry. This thin layer consists of dead, anucleate, keratinised cells embedded in a lipid matrix. The stratum corneum serves to regulate water loss from the body whilst preventing the entry of harmful materials, including microorganisms. Typically, it takes 14 daysfor a cell from the stratum basale to differentiate into a stratum corneum cell, and the stratum corneum cells are typically retained for a further 14 days prior to shedding. 2) Melanocyte The melanocyte is a dendritic, pigment-synthesizing cell derived from neural crest that is confined mainly to the basal layer. Differentiation of the melanocyte correlates with the acquisition of its primary functions: melanogenesis, arborization, and transfer of pigment to keratinocytes. There are important organizational relationships and functional interactions between keratinocytes and melanocytes that the melanocyte depends on for differentiation and function. Approximately 36 basal and suprabasal keratinocytes are thought to coexist functionally with each melanocyte in an epidermal melanin unit. 3) The Langerhan’s cell Langerhans cells are bone marrow–derived, antigen-processing and -presenting cells that are involved in a variety of T cell responses. Langerhans cells are dendritic and do not form junctions with any of the cells. They are distributed in the basal, spinous, and granular layers, showing a preference for a suprabasal position. Langerhans cells migrate from the bone marrow to the circulation into the epidermis early in embryonic development and continue to repopulate the epidermis throughout life. A number of the markers expressed by the Langerhans cell are characteristic for other cells of the monocyte–macrophage lineage and provide some insight into their function. Langerhans cells are the primary cells in the epidermis responsible for the recognition, uptake, processing, and presentation of soluble antigen and haptens to sensitized T lymphocytes, and are implicated in the pathologic mechanisms underlying cutaneous immunological disorders. 2. Epidermal appendages Pilosebaceous units, eccrine and apocrine glands and nails constitute epidermal appendages. Embryologically, they are ectodermal in origin. 1) Hair follicle Hair can be found in varying densities of growth over the entire surface of the body, exceptions being on the palms, soles and glans penis. Follicles are most dense on the scalp and face. Each hair follicle is lined by germinative cells, which produce keratin; and by melanocytes, which synthesize pigment. The hair shaft consists of an outer cuticle, a
cortex of keratinocytes and an inner medulla. The root sheath, which surrounds the hair bulb, is composed of an outer and inner layer. An erector pili muscle is assoc iated with the hair shaft and contracts with cold, fear and emotion to pull the hair erect, giv ing the skin goose bumps During the growing phase or anagen, the cells of the hair bulb actively devide and produce the growing hair. Then hair follicles go into the catagen, or transitional phase of activity, the matrix cells stop dividing. During catagen, the lower protion of the follicle disappears, leav ing behind a thin strand of epithelial cells surrounded by a thick basement membrane zone. During telogen, the ep ithelial strand subsequently shortens to the level of the arrector pili muscle 2) Sebaceous gland Sebaceous glands are derived from epidermal cells and are closely associated with hair follicles. Sebaceous glands are found in greatest abundance on the face and scalp, though they are distributed throughout all skin sites except the palms and soles. They are small in children, enlarging and becoming active at puberty, being sensitive to androgens. They produce an oily sebum by holocrine secretion in which the cells break down and release their lipid cytoplasm 3)Sweat glands Sweat glands are thought to be over 2.5 million on the skin surface and they are present over the majority of the body They are located within the dermis and are composed of coiled tubes, which secrete a watery substance They are classified into two different types: eccrine and apocrin a. Eccrine glands are found all over the skin especially on the palms, soles, axillae forehead. They are under psychological and thermal control. Sympathetic(choliner nerve fibres innervate eccrine glands. The watery fluid they secrete contains chloride, lactic acid, fatty acids, urea, glycoproteins and mucopolysaccharides b. apocrine glands are larger, the ducts of which empty out into the hair follicles. They are present in the axillae, anogenital region and areolae and are under thermal control They become active at puberty, producing a protein-rich secretion which when acted upon by skin bacteria gives out a characteristic odour. These glands are under the control f sympathetic( energi ic)nerve fibr 4)Nails Nails consist of a dense plate of hardened keratin between 0.3 and 0. 5mm thick The nail is made up of a nail bed, nail matrix and a nail plate. The nail matrix is composed of dividing keratinocytes, which mature and keratinise into the nail plate. Underneath the nail plate lies the nail bed. The nail plate appears pink due to adjacent dermal capillaries and the white lunula at the base of the plate. The thickened epidermis which underlies the free margin of the nail at the proximal end is called the hyponychium. Fingernails grow at 0. 1 mm per day; the toenails more slowly 2. Dermis The dermis derives from mesoderm, and is typically 3-5 mm thick and is the major component of human skin. It is composed of a network of connective tissue, predominantly collagen fibrils providing support and elastic tissue providing flexibility The dermis has numerous structures embedded within it: blood and lymphatic vessels nerve endings, pilosebaceous units and sweat glands(eccrine and apocrine). The extensive vasculature of the skin is essential for regulation of body temperature whilst
cortex of keratinocytes and an inner medulla. The root sheath, which surrounds the hair bulb, is composed of an outer and inner layer. An erector pili muscle is associated with the hair shaft and contracts with cold, fear and emotion to pull the hair erect, giving the skin `goose bumps'. During the growing phase or anagen, the cells of the hair bulb actively devide and produce the growing hair. Then hair follicles go into the catagen, or transitional phase of activity, the matrix cells stop dividing. During catagen, the lower protion of the follicle disappears, leaving behind a thin strand of epithelial cells surrounded by a thick basement membrane zone. During telogen, the epithelial strand subsequently shortens to the level of the arrector pili muscle. 2) Sebaceous gland Sebaceous glands are derived from epidermal cells and are closely associated with hair follicles. Sebaceous glands are found in greatest abundance on the face and scalp, though they are distributed throughout all skin sites except the palms and soles. They are small in children, enlarging and becoming active at puberty, being sensitive to androgens. They produce an oily sebum by holocrine secretion in which the cells break down and release their lipid cytoplasm. 3) Sweat glands Sweat glands are thought to be over 2.5 million on the skin surface and they are present over the majority of the body. They are located within the dermis and are composed of coiled tubes, which secrete a watery substance. They are classified into two different types: eccrine and apocrine. a. Eccrine glands are found all over the skin especially on the palms, soles, axillae and forehead. They are under psychological and thermal control. Sympathetic (cholinergic) nerve fibres innervate eccrine glands. The watery fluid they secrete contains chloride, lactic acid, fatty acids, urea, glycoproteins and mucopolysaccharides. b. Apocrine glands are larger, the ducts of which empty out into the hair follicles. They are present in the axillae, anogenital region and areolae and are under thermal control. They become active at puberty, producing a protein-rich secretion which when acted upon by skin bacteria gives out a characteristic odour. These glands are under the control of sympathetic (adrenergic) nerve fibres. 4) Nails Nails consist of a dense plate of hardened keratin between 0.3 and 0.5mm thick. The nail is made up of a nail bed, nail matrix and a nail plate. The nail matrix is composed of dividing keratinocytes, which mature and keratinise into the nail plate. Underneath the nail plate lies the nail bed. The nail plate appears pink due to adjacent dermal capillaries and the white lunula at the base of the plate. The thickened epidermis which underlies the free margin of the nail at the proximal end is called the hyponychium. Fingernails grow at 0.1 mm per day; the toenails more slowly. 2. Dermis The dermis derives from mesoderm, and is typically 3–5 mm thick and is the major component of human skin. It is composed of a network of connective tissue, predominantly collagen fibrils providing support and elastic tissue providing flexibility. The dermis has numerous structures embedded within it: blood and lymphatic vessels, nerve endings, pilosebaceous units and sweat glands (eccrine and apocrine). The extensive vasculature of the skin is essential for regulation of body temperature whilst