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Other Papulosquamous Disorders

Small Plaque Parapsoriasis Synonyms ▪ Parapsoriasis en plaques ▪ Chronic superficial [scaly] dermatitis ▪ Digitate dermatosis (variant) ▪ Xanthoerythrodermia perstans (variant) Key features ▪ Chronic, asymptomatic, erythematous scaly patches ▪ Lesions are generally <5 cm in diameter or digitate ▪ Histologically, mild, nonspecific spongiotic dermatitis with parakeratosis is seen ▪ There is a predominance of CD4 + T cells in the lymphocytic infiltrate ▪ A dominant T-cell…

Psoriasis

Key features ▪ Psoriasis is a chronic, immune-mediated disorder that results from a polygenic predisposition combined with environmental triggers, e.g. trauma, infections, medications, psychological stress ▪ The underlying pathophysiology involves various classes of T cells and their interactions with dendritic cells and cells involved in innate immunity, including neutrophils and keratinocytes ▪ Identification of susceptibility genes has pointed to a major role for the innate and…

Psychocutaneous Diseases

Introduction “Psychodermatology” refers to any aspect of dermatology in which psychological factors play a significant role. At least a third of patients seen in dermatology practices require consideration of associated emotional and psychosocial factors for effective management of their skin condition . Many patients with psychodermatologic problems resist referral to a mental health professional, and some become upset if such a referral is suggested. Ironically, the…

Pruritus and Dysesthesia

Introduction Pruritus can be defined as an unpleasant sensation that elicits a desire to scratch. The presumed biologic purpose of pruritus is to provoke scratching to remove a parasite or other harmful pruritogen. Pruritus is the most common skin-related symptom. It often arises from a primary cutaneous disorder but represents a manifestation of an underlying systemic disease in ~10–25% of affected individuals . Non-dermatologic conditions that…

Cutaneous Neurophysiology

Key features ▪ Two subsets of pruritoceptive C neurons that respond to histamine versus cowhage and then activate distinct spinothalamic tract neurons ▪ Peripheral itch mediators include histamine, proteases, and interleukin-31, while central itch mediators include opioids, gastrin-releasing peptide, and B-type natriuretic peptide ▪ There is an overlap between chronic itch and chronic pain, including activation of multiple brain areas and associated neuromediators and receptors, e.g.…

Immunology

Key features ▪ The major purpose of the immune system is protection against harmful organisms. This is achieved by a rapid “primitive” reaction, called the innate immune response, and a more highly developed specific reaction, called the adaptive immune response ▪ The characteristics of an adaptive immune response are specificity and the accumulation of memory, thus enabling improvement with each successive encounter with a particular antigen…

Molecular Biology

Introduction Advances in molecular biology are rapidly changing our understanding of skin biology and disease. Increased knowledge is being translated into new molecular diagnostic tests that are transforming the clinical practice of dermatology. Molecular analyses are currently being employed to diagnose genodermatoses , cutaneous infections , melanomas , lymphomas , and inherited or autoimmune blistering disorders . In order to use these tests in a prudent…

Skin Development and Maintenance

Introduction Development of the human embryo is a complex process involving highly orchestrated cell movements, proliferation, death, and differentiation. This chapter focuses on key events and regulatory mechanisms that result in skin morphogenesis, maintenance, and regeneration. The spectrum of cutaneous abnormalities that can result from mutations in genes with critical roles in skin development is discussed. Ultimately, improved understanding of the pathways and signaling cascades that…

Anatomy and Physiology

Key features ▪ The relationship between function and structure of the skin is best demonstrated by presenting diseases that illustrate how skin can fail. Thus, disease reveals function, and function illustrates structure ▪ The most obvious function of skin is to maintain an internal environment that allows an organism to protect DNA and to reproduce it relatively faithfully ▪ Cutaneous structures include an epidermis that serves…

Basic Principles of Dermatology

Introduction to Clinical Dermatology The skin represents the largest organ of the human body. The average adult has 1.75 m 2 (18.5 ft 2 ) of skin that contains a variety of complex adnexal structures, including hair follicles, nails, glands and specialized sensory structures, all of which function in protection, homeostasis, and the transmission of sensation. Dermatology is the field of medicine that deals with the macroscopic study…

Principles of Systemic Drug Use

Key Points Systemic medications used for dermatologic conditions are associated with risks. The choice of systemic medication requires assessment of the disease severity and the performance of a risk–risk analysis balancing the risk of the disease with the risks of the medication. Patients should be made aware of the Food and Drug Administration indications for the selected systemic medication and the basis for off-label use. Systemic…

Cutaneous Drug Eruptions

Key Points Prevent harm: Be aware of high-risk drugs and always consider a drug reaction as part of a differential diagnosis. Monitoring: Monitor for systemic involvement. Diagnosis: Determine the morphology of the eruption and decide if it is simple or complex. Management and treatment: After a causality assessment, stop most likely potential drugs when clinically appropriate. Introduction Cutaneous drug reactions account for a large proportion of…

Leg Ulcers

Key Points Venous leg ulcerations are the most common cause of leg ulcers, followed by mixed venous/arterial disease and arterial insufficiency. However, up to 10% of leg ulcers are due to atypical etiologies, infections, metabolic disorders, neoplasms, and inflammatory processes. Venous insufficiency or dysfunction is caused by outflow abnormalities or venous reflux, resulting in sustained ambulatory venous pressures or venous hypertension. Arterial insufficiency results from failure…

Oral Disease

Key Points A thorough examination of the intraoral soft tissues, including palpation, is necessary to detect the subtle signs of systemic disease as well as localized problems such as leukoplakia. Autosomal dominant cancer syndromes may present with diverse mucous membrane manifestations: odontogenic keratocysts in nevoid basal cell carcinoma syndrome; papillomatosis in multiple hamartoma and neoplasia syndrome; pigmented macules in Peutz–Jeghers syndrome. The mat-like telangiectases of the…

Nail Signs of Systemic Disease

Key Points A complete and detailed history and physical examination of all 20 nails is essential in evaluating patients with suspected manifestations of systemic disease. Subacute bacterial endocarditis is the most common systemic cause of splinter hemorrhages, which occur proximally and are typically present in multiple nails. Muehrcke lines, half-and-half nails, and Terry nails are all examples of apparent leukonychia, in which there is abnormal nail…

Hair Disorders in Systemic Disease

Key Points Hair loss in the setting of systemic disease may occur through one of five mechanisms: telogen effluvium, anagen arrest, hair miniaturization, scarring alopecia, and hair shaft disorders. The most common cause of hair loss is telogen effluvium, which can be divided into five subtypes depending on which portion of the hair cycle is pathologically lengthened or shortened. Anagen arrest occurs when there is a…

Mast Cell Disease

Key Points Mastocytosis is a disease of both children and adults. Most children have skin-limited disease and an excellent prognosis. Many adults have either cutaneous only or indolent systemic mastocytosis, and a very good prognosis. Patients with more advanced disease have a worse prognosis, which may include the development of a second hematologic malignancy. The diagnosis is established by demonstrating increased mast cells in the skin…

Pregnancy

Key Points Physiologic changes associated with pregnancy have effects on the skin including pigmentary changes such as linea nigra and melasma; vascular changes such as telangiectasia, varicosities, and spider angiomata; connective tissue changes such as striae distensae; and changes on glandular structures, hair, nails, and mucosal surfaces. Pregnancy can also impact neoplasms both benign and malignant. There is a variable and often unpredictable effect of pregnancy…

Neurocutaneous Disease

Key Points Neurofibromatosis is an autosomal dominant disorder characterized by cutaneous neurofibromas, café-au-lait macules, and myriad systemic features with marked variability of expression. Patients with neurofibromatosis are at risk for the development of a malignant peripheral nerve sheath tumor. Increasing or constant pain, change in consistency, or rapid growth of a nodule within an existing plexiform neurofibroma are concerning signs of malignant transformation. Tuberous sclerosis complex…

Cutaneous Manifestations Observed in Transplant Recipients

Key Points Skin infections occur at a great frequency in solid organ and bone marrow transplant recipients largely as a consequence of immunosuppression. Neoplasms, particularly squamous cell carcinomas, occur at greater frequency, are more difficult to manage, and are more likely to metastasize than in the nontransplant population. Graft-versus-host disease, particularly the chronic variant, remains a problem, particularly among patients with bone marrow or stem cell…