The visible pigmentation of the skin or hair is a combination of the amount of melanin, type of melanin (eumelanin vs. pheomelanin), degree of vascularity, presence of carotene, and thickness of the stratum corneum. Other materials can be deposited abnormally…
Raynaud Phenomenon and Raynaud Disease Raynaud phenomenon is characterized by episodic, recurrent vasospasm of the fingers and toes resulting in white, blue, and red discoloration provoked by cold or stress. When it occurs in the presence of an associated disease,…
Lesions on the mucous membranes may be more difficult to diagnose than lesions on the skin, and not merely because they are less easily and less often seen. There is less contrast of color and greater likelihood of alterations in…
Diseases of the Hair Normal human hairs can be classified according to cyclic phases of growth. Anagen hairs are growing hairs; catagen hairs are those undergoing transition from the growing to the resting stage; and telogen hairs are resting hairs,…
Cutaneous Lymphoid Hyperplasia (Lymphocytoma Cutis, Lymphadenosis Benigna Cutis, Pseudolymphoma) Benign cutaneous lymphoid hyperplasia can be caused by medications, injected foreign substances, infections, and arthropod bites, or it may be idiopathic. If there is a histologic resemblance to lymphoma, the term…
Granulatomatous reactions generally represent patterns of chronic inflammation that may take a long time to develop and a long time to respond to treatment. Granulomatous inflammation can occur in the setting of inflammatory disorders (autoimmune, autoinflammatory), medication reactions, malignancies, and…
Melanocytes originate in the embryonal neural crest and migrate to the epidermis, dermis, leptomeninges, retina, mucous membrane epithelium, inner ear, cochlea, and vestibular system. Nevus cells are a form of melanocyte with a tendency to aggregate into clusters of cells.…
Epidermal Nevi Epidermal nevi are hamartomatous growths of the epidermis that are present at birth in about half of patients or develop early in childhood. The term epidermal nevus includes several entities, including keratinocytic epidermal nevi, nevus sebaceus, and nevus…
In this chapter proliferations derived from vascular endothelial cells, fibroblasts, myofibroblasts, smooth muscle cells, Schwann cells, and lipocytes are reviewed. Also discussed are several neoplasms of cells invading or aberrantly present in the dermis, such as metastatic cancer, endometriosis, and…
The genetic basis for common diseases such as atopic dermatitis and psoriasis, in addition to rare diseases, has been partially elucidated. Some genetic disorders are explained by mutations in a specific gene or genes that lead to a specific clinical…