Photo Facts The UV radiation (UVR) emitted by the sun is arbitrarily subdivided based on wavelength into UVA (400–320 nm), UVB (320–290 nm), and UVC (290–200 nm). More than 95% of UVR that reaches the earth’s surface is UVA. UVA, but not UVB, can penetrate through glass windows. The penetration of UVR into the skin is wavelength-dependent ( Fig. 73.1 ). Principles and formulations of sunscreens…

Insects The bite of any insect can lead to a local cutaneous reaction whose intensity can vary depending on the individual’s level of sensitivity; the typical presentation is a 2- to 8-mm, erythematous urticarial papule in an exposed area ( Fig. 72.1 ); lesions are often multiple and can be grouped ( Fig. 72.2 ). Secondary changes consisting of excoriations may be present; less often, vesicles…

Scabies Infestation by Sarcoptes scabiei var . hominis , a mite that lives within the stratum corneum of human skin ( Fig. 71.1 ). Transmission is primarily by direct contact with an infested person and occasionally by fomites (e.g. clothing); incubation period may be up to 6 weeks; in some tropical regions, scabies can infest the majority of individuals in a community. Asymptomatic infestation by scabies…

Leishmaniasis Three major forms: (1) cutaneous ( Fig. 70.1 ); (2) mucocutaneous ( Fig. 70.2 ); and (3) visceral (e.g. liver, spleen). Caused by more than 15 different species of Leishmania ( Table 70.1 ). Table 70.1 Four major species of Leishmania that cause cutaneous disease. Complex Species Major geographic distribution Leishmania tropica L. major Arid areas of Africa (north and south of the Sahara), Middle…

In this chapter, five sexually transmitted infections (STIs) are covered – syphilis, gonorrhea, chancroid, lymphogranuloma venereum (LGV), and granuloma inguinale. Additional more common STIs including herpes simplex infections, mollusca contagiosa, condyloma acuminata, pubic lice, and HIV infection are discussed in Chapter 65, Chapter 66, Chapter 67, Chapter 68, Chapter 71 , respectively. When one STI is present, a search for others is indicated. Syphilis (Lues) Etiologic…

Viral infections frequently have cutaneous manifestations, especially in children. This chapter covers classic childhood exanthems, poxvirus infections, and several other viral infections with characteristic skin findings. Nonspecific viral exanthems , typically presenting with blanchable erythematous macules and papules in a widespread distribution, are also common in children infected with enteroviruses (see below) and a variety of respiratory viruses, generally resolving spontaneously within a week. Fig. 68.1…

General Human herpesviruses (HHV) are a family of double-stranded DNA viruses (8 members) with a lipid envelope. All share the ability to establish lifelong latency in their host following primary infection. Basic pathogenesis of HHV infections involves a sequence of primary infection, establishment of latency, reactivation, and recurrent (secondary) infection. Clinical presentations depend on the host’s age, anatomic location, immune status, and ethnicity (e.g. EBV). Spread…

Key Points Human papilloma viruses (HPV) comprise a large group of at least 200 genotypes of DNA viruses that infect the skin and mucosa. Different genotypes cause different skin lesions ( Table 66.1 ). – Clinical variants differ as to anatomic location, morphology, histopathology, and HPV subtype; correlation of clinical and histopathologic findings is particularly important for bowenoid papulosis and verrucous carcinoma in order to prevent…

There are a number of cutaneous disorders that point to the diagnosis of HIV infection. For some, it is the mere presence of the skin disease, whereas for others, the disease is extensive or proves recalcitrant to therapy ( Table 65.1 ; Figs 65.1–65.14 ). As HIV infection is associated with immunosuppression, the clinical presentation of various infectious diseases is often reminiscent of that observed in…

Key Points Cutaneous fungal diseases can be broadly divided into two groups: – Superficial – limited to the stratum corneum, hair, and/or nails – Deep – dermal and/or subcutaneous Superficial fungal infections can be further subdivided into: – Non-inflammatory – most commonly tinea versicolor, but includes tinea nigra and piedra – Inflammatory – primarily infections due to dermatophytes ( Trichophyton , Microsporum , Epidermophyton ; e.g.…

Rickettsial infections often have cutaneous manifestations that can vary from nonspecific maculopapular eruptions to an eschar at the site of inoculation (by the vector) to petechiae and retiform purpura ( Table 63.1 ). These Gram-negative bacteria reside within an arthropod – tick, flea, mite, or louse – during a portion of their life cycle and are transmitted to humans while feeding, either via saliva or via…

Key Points Mycobacteria are the etiologic agents of three major types of infection: – Leprosy – Mycobacterium leprae – Tuberculosis – Mycobacterium tuberculosis – Atypical or nontuberculous infections – e.g. Mycobacterium marinum, Mycobacterium chelonae ( Tables 62.1 and 62.2 ) Table 62.1 Mycobacteria that cause cutaneous disease. Modified classification of Runyon from: Hautmann G, Lotti T. Atypical mycobacterial infections of the skin. Dermatol Clin 1994;12:657–68; Yates…

The skin is normally colonized by hundreds of species of bacteria as part of the cutaneous microbiota (flora). These organisms help prevent skin infection by competing with pathogenic microorganisms. Skin infection with bacteria may be a primary problem (e.g. impetigo) or a complication of another skin disease (e.g. atopic dermatitis) and may lead to multisystem dysfunction (e.g. toxic shock syndrome). Nomenclature of these diseases often reflects…

Introduction The anatomy ( Fig. 60.1 ), normal cutaneous findings, and benign lesions of the anogenital area ( Table 60.1 ) should be appreciated before addressing diseases in this area. Table 60.1 Normal findings and benign lesions of the anogenital region. Papules in the anogenital region can also result from HPV infection, in particular condylomata acuminata and common warts (see Ch. 66 ). Common Less common…

In addition to common benign lesions such as bite fibromas and mucoceles, oral findings can represent clues to the diagnosis of skin disorders (e.g. lichen planus, early pemphigus vulgaris) or cutaneous signs of systemic disease ( Table 59.1 ). Table 59.2 provides an overview of topical care for oral inflammatory conditions. Table 59.1 Systemic diseases with oral manifestations. Disorder Oral findings Primary systemic amyloidosis (see Ch.…

The nail matrix, which is the growth area, has proximal and distal components ( Fig. 58.1 ). – The proximal nail matrix forms the top (surface) of the nail plate – The distal nail matrix forms the underside of the nail plate; therefore, biopsies of the distal matrix are less likely to produce a deformity of the surface of the nail plate Fingernails grow ∼1–3 mm…

Definitions Hypertrichosis : excessive hair growth on any area of the body, beyond what is normally expected for a patient’s demographic group. Hirsutism : excessive terminal hair growth in women or children in a pattern typically seen in adult men. Lanugo hair : long fine hair that is grown in utero , covers the fetus, and is normally shed either in utero or during the first…

In a normal scalp, 90–95% of hairs are in anagen phase, 5–10% in telogen phase ( Fig. 56.1 ). About 50–100 hairs normally shed daily. Alopecias can be categorized as diffuse vs circumscribed, patterned vs non-patterned, and non-scarring vs scarring loss ( Fig. 56.2 ). Non-Scarring Alopecias Male and Female Pattern Hair Loss (Androgenetic Alopecia) 80% of Caucasian men are affected by age 70 years. Women…

Definitions Hyperpigmentation : a term used to describe disorders characterized by darkening of the skin; encompasses hypermelanosis. Hypermelanosis : a more specific term that denotes an increase in the melanin content of the skin; typically due to an increase in melanin production but occasionally from an increase in the density of active melanocytes. Discoloration : a term used to describe an abnormal color of the skin;…

Introduction/Definitions Leukoderma and hypopigmentation : areas of skin are lighter in color than uninvolved skin, due primarily to a decrease in melanin; decreased blood supply to the skin (e.g. nevus anemicus) can be another cause of leukoderma. Hypomelanosis : an absence or reduction of melanin in the skin that may be due to any one or a combination of the following: 1. A decrease in the…