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Foreign Body Reactions

Key features ▪ Foreign body reactions represent inflammatory responses to inorganic and high-molecular-weight organic materials that have been introduced into the skin and are variably resistant to degradation ▪ Routes of introduction can vary from accidental or self-inflicted to surgical and cosmetic procedures to topical application of various compounds ▪ The most common clinical presentation is red to red–brown papules, nodules or plaques (with or without…

Non-infectious Granulomas

Introduction The granulomatous diseases discussed in this chapter may be defined as having an inflammatory cutaneous infiltrate in which histiocytes are the preponderant inflammatory cells. While cutaneous sarcoidosis is the prototype of non-infectious (sterile) granulomatous dermatitides, there are a number of other entities in this group ( Fig. 93.1 & Table 93.1 ). Additional non-infectious granulomatous disorders are covered in other chapters, including rheumatoid nodules in…

Xanthomas

Key features ▪ Cutaneous xanthomas can signal the presence of an underlying hyperlipidemia or monoclonal gammopathy ▪ An understanding of basic lipid metabolism provides insight into the underlying hyperlipoproteinemias as well as the formation of xanthomas ▪ The major forms of xanthomas associated with hyperlipidemia are: eruptive, tuberous, tendinous and plane (including xanthelasma) ▪ Normolipemic plane xanthomas occur in association with monoclonal gammopathies ▪ Histologically, lipid-laden…

Histiocytoses

Overview The histiocytoses represent a group of proliferative disorders that share a common CD34 + progenitor cell in the bone marrow. Three “histiocytes” of cutaneous importance are: (1) the Langerhans cell , which migrates to and from the epidermis and functions as a potent antigen-presenting cell (APC); (2) the mononuclear cell/macrophage (sometimes called the “true” histiocyte), which migrates to and from the dermis and has both…

Skin Signs of Abuse

Child Abuse Synonym ▪ Battered child syndrome Key features ▪ Signs of physical abuse include: unexplained bruises; injuries of the thorax, abdomen, buttocks, genitals, chin, ears, or neck; curvilinear marks; and cigarette burns or other well-demarcated burns ▪ Signs of sexual abuse include attenuation, fresh tears, or scars of the hymen and the anal margin extending out onto perianal skin Introduction Child abuse encompasses the broad…

Signs of Drug Abuse

Introduction According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), the essential feature of a substance use disorder is a cluster of cognitive, behavioral, and physiologic symptoms whereby an individual continues to use a substance despite significant substance-related problems. Diagnosis of substance use disorder is based on a pathologic pattern of behaviors including impaired control, social impairment, risky use, and the pharmacologic criteria of…

Environmental and Sports-Related Skin Diseases

The skin is our primary interface with the environment. Amongst Earth's creatures, humans are unique in their ability to manipulate the environment by manufacturing clothing, shelter, and heating or cooling devices to allow them to live in a variety of environmental extremes. Despite technologic advances that have allowed humans to live, work and play in most of the environments on this planet, deliberate or inadvertent exposure…

Photodermatologic Disorders

All skin can react to light because it contains molecules (chromophores) whose chemical structures are capable of absorbing ultraviolet radiation (UVR) or other electromagnetic energy. This absorbed energy is then either re-emitted harmlessly as biologically inactive radiation or diverted to driving thermochemical reactions, leading to molecular, cellular, tissue, and clinical changes. These alterations are subsequently repaired or result in permanent effects. Nucleic acids are the most…

Ultraviolet Radiation

Key features ▪ Exposure of the skin to UV light has acute, short-term effects and chronic, long-term effects, both of which are wavelength-dependent. Profound effects also occur with non-erythemogenic doses of UV light ▪ UV light affects the skin's immune system, exerting both pro- and anti-inflammatory responses ▪ UV light induces several different types of DNA damage in a wavelength-dependent manner, such as pyrimidine dimers (UVB…

Bites and Stings

Insects Insect Bites and Stings (Class Insecta) Key features ▪ Pruritic papules sometimes progress to vesiculobullae or persistent prurigo nodularis-like lesions ▪ Papular urticaria may be localized to sites of bites or generalized ▪ Pseudolymphomatous reactions occasionally occur ▪ Anaphylaxis is mainly related to hymenopterid stings ▪ Secondary infection is most often staphylococcal Introduction Insect bites and stings are prevalent throughout the world. In temperate climates…

Infestations

Scabies Synonyms ▪ Itch mite infestation ▪ “Seven-year itch” Key features ▪ Human scabies is a pruritic condition caused by infestation with the host-specific mite Sarcoptes scabiei var. hominis , which lives its entire life within the epidermis ▪ Although the scabies mite is not a known vector for any systemic disease, secondary bacterial infections with Streptococcus pyogenes or Staphylococcus aureus may develop ▪ Transmission typically…

Protozoa and Worms

Key features ▪ Protozoa are responsible for many tropical diseases that not only affect large regions of the world but also can have different clinical presentations in the Old World versus the New World (e.g. leishmaniasis) ▪ Protozoal infections can lead to significant morbidity in both immunocompromised hosts (e.g. toxoplasmosis) and immunocompetent individuals (e.g. Balamuthia spp.) ▪ Worms (helminths) are common parasites with a worldwide distribution;…

Sexually Transmitted Infections

Introduction The term “venereal diseases” was historically used to refer to infections that are sexually transmitted, i.e. syphilis, gonorrhea, chancroid, lymphogranuloma venereum, and granuloma inguinale. These disorders are now referred to as “sexually transmitted diseases” (STDs) or “sexually transmitted infections” (STIs), terms that directly reflect recognition that they are caused predominantly by sexual contact with an infected person. For infections caused by pathogens for which non-sexual…

Other Viral Diseases

Introduction Viral infections are frequently associated with cutaneous manifestations, especially in children, in whom they are the most common cause of exanthems. An exanthem is defined as a skin eruption occurring as a sign of a general disease. Viral exanthems may present with distinctive cutaneous features or in an entirely nonspecific fashion, and at times they may pose a significant diagnostic challenge, even to the most…

Human Herpesviruses

The human herpesviruses (HHVs) are categorized into three groups: alpha, beta, and gamma herpesvirinae ( Table 80.1 ). Each virus contains a core of linear double-stranded DNA, an icosahedral capsid 100–110 nm in diameter, and an envelope with glycoprotein spikes on its surface. The pathogenesis of herpesvirus infections follows the sequence of primary infection, latency, and reactivation. The eight human herpesviruses are discussed in this chapter and…

Human Papillomaviruses

Synonyms ▪ Verrucae vulgares (singular: verruca vulgaris) – common warts ▪ Verrucae palmares et plantares – hand and foot warts ▪ Verrucae planae – flat warts, plane warts ▪ Condylomata acuminata (singular: condyloma acuminatum) – genital warts ▪ Condylomata plana – flat cervical condylomas, plane condylomas ▪ Squamous intraepithelial lesion (SIL) – cervical intraepithelial neoplasia (CIN); vulvar (VIN); vaginal (VaIN); penile (PIN); anal (AIN) ▪ Buschke–Löwenstein…

Cutaneous Manifestations of HIV Infection

Key features ▪ A broad spectrum of infectious, inflammatory, and neoplastic skin conditions may occur in the setting of HIV-induced immune dysfunction ▪ The cutaneous findings often correlate with immune status, and knowing the viral load and CD4 + T-cell count can help to generate a more focused differential diagnosis ▪ The possibility of HIV infection should be considered when patients present with severe, unusual, and…

Fungal Diseases

Key features ▪ Cutaneous fungal infections are broadly divided into two groups: (1) those that are limited to the stratum corneum, hair, and nails; and (2) those that involve the dermis and subcutaneous tissues ▪ Superficial fungal infections of the skin are most often due to dermatophytes and Candida spp. ▪ “Subcutaneous” mycoses are often the result of implantation, while systemic or “deep” mycoses of the…

Rickettsial Diseases

Key features ▪ Rickettsiae are small, obligately intracellular, Gram-negative bacteria that reside within an arthropod host (tick, flea, louse, or mite) during part of their life cycle ▪ The arthropod vector transmits the rickettsiae in its saliva or feces during feeding ▪ The major vertebrate target cells of Rickettsia (endothelium), Orientia (endothelium), Ehrlichia (monocytes or neutrophils), Anaplasma (neutrophils), and Coxiella (macrophages) determine to a large degree…

Mycobacterial Infections

In 1896, the name “mycobacteria” was given to a large group of bacteria that produce filamentous pellicles similar to molds when grown in liquid media. These organisms are thin, slightly curved to straight, non-motile and non-spore-forming, with a waxy coating that makes them resistant to most stains. Mycobacteria are also acid-fast, which means they are not readily decolorized by acid after staining . A number of…