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…
Developmental anomalies are a diverse group of congenital disorders that result from faulty in utero morphogenesis. When they affect the skin, developmental anomalies can range in severity from isolated minor physical findings to potentially life-threatening conditions or cutaneous signs of significant extracutaneous defects. Midline Lesions of the Nose or Scalp A midline mass or pit on the nose or scalp due to a dermoid cyst, cephalocele,…
This chapter discusses genetic skin diseases that are not covered in other chapters, including conditions featuring extracutaneous tumorigenesis, enzyme deficiencies, premature aging, and ectodermal dysplasia. Disorders Featuring Extracutaneous Tumorigenesis Cowden Syndrome and OtherForms of PTEN Hamartoma Tumor Syndrome Spectrum of autosomal dominant multisystem disorders that feature characteristic skin findings ( Fig. 52.1 ), macrocephaly, hamartomatous overgrowth of a variety of tissues, and a predisposition to certain…
A mosaic organism is composed of ≥2 genetically distinct cell populations derived from a homogeneous zygote. – Genomic mosaicism results from alteration in the DNA sequence, affecting genes or chromosomes – Functional (epigenetic) mosaicism results from changes in gene expression (but not the DNA sequence) that are passed on during cellular replication; an important example is lyonization in female embryos, where random inactivation of one of…
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Ichthyoses and erythrokeratodermas represent a diverse group of disorders of cornification, which are characterized by a defective epidermal barrier due to abnormal differentiation and/or desquamation of keratinocytes. Ichthyoses feature diffuse scaling of the skin, often in a widespread distribution, whereas erythrokeratodermas present with circumscribed areas of hyperkeratosis without prominent scaling. These conditions usually have a genetic basis, with the occasional exception of acquired ichthyosis associated with…
Introduction Recognizing the skin signs of systemic disease is an important aspect of dermatology; however, the vast number of cutaneous manifestations, combined with the infrequency with which each sign is encountered, can be daunting. The approach in this chapter is to provide several examples of the most commonly observed or most characteristic cutaneous findings, based on the organ system most often involved – for example, papulonodules…
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Malnutrition Poor nutrition resulting from an insufficient or poorly balanced diet or from defective digestion or utilization of foods. Malnutrition encompasses both deficiencies and excesses (e.g. obesity) ( Fig. 43.1 ; Tables 43.1 and 43.2 ). Table 43.1 Malnutrition-deficiency syndromes with mucocutaneous manifestations. Deficiency syndrome Mucocutaneous features Systemic features Marasmus (see Fig. 43.2 ) Xerotic, thin, pale, lax, wrinkled skin Occasionally fine scaling and hyperpigmentation Follicular…
There are four major forms of cutaneous calcification (calcinosis cutis): (1) dystrophic – locally within sites of pre-existing skin damage; (2) metastatic – due to systemic metabolic derangements; (3) iatrogenic – secondary to medical treatment or testing; and (4) idiopathic . An occasional patient will have a mixed form. Cutaneous ossification (osteoma cutis) occurs in the setting of several genetic disorders, in a miliary form on…
The porphyrias represent a group of metabolic disorders in which there is dysfunction of the enzymes involved in heme synthesis ( Fig. 41.1 ). With the exception of acquired porphyria cutanea tarda (PCT), the underlying etiology is monogenetic mutations. Porphyrins absorb light energy (400–410 nm) and their accumulation within the skin can lead to photosensitization, with water-soluble porphyrins producing blisters and lipophilic porphyrins leading to acute…
A heterogeneous group of disorders in which there are deposits, usually of endogenous materials, within the skin. Entities belonging to this group that are covered in other chapters include mucinoses ( Ch. 38 ), amyloidosis ( Ch. 39 ), porphyrias ( Ch. 41 ), and calcinosis cutis ( Ch. 42 ). Gout Metabolic disorder in which there is hyperuricemia due to increased production and/or decreased excretion…
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In this group of disorders, there is deposition of glycosaminoglycans, previously referred to as mucopolysaccharides (“mucin”), within the skin, especially the dermis. Most often, the deposit is composed of hyaluronic acid. While several of the entities are idiopathic, underlying disorders include autoimmune thyroid disease, a monoclonal gammopathy, diabetes mellitus, and LE. Scleredema Symmetric diffuse induration of the skin, usually limited to the upper back and posterior…
Systemic-Onset Juvenile Idiopathic Arthritis (SoJIA; Still Disease) and Adult-Onset Still Disease (AoSD) Among the major types of juvenile idiopathic arthritis (JIA; formerly juvenile rheumatoid arthritis [JRA]), cutaneous manifestations are most common in SoJIA, psoriatic arthritis (see Ch. 6 ), and rheumatoid factor (RF)-positive polyarthritis (rheumatoid nodules and other findings similar to rheumatoid arthritis [RA]; see below). SoJIA can develop at any age prior to 16 years…