Addison's Disease Addison's disease (chronic primary adrenocortical insufficiency) occurs when the adrenal gland has lost most of its functional capacity. Addison's disease can be caused by many different disease states that inhibit the functioning of the adrenal gland. The adrenal…
Beriberi Beriberi is a nutritional deficiency state that is caused directly by a lack of thiamine (vitamin B 1 ) in one's diet or by a lack of proper absorption of the vitamin. A rare form of acquired thiamine deficiency…
Alopecia Areata Alopecia areata is an autoimmune disease that causes discrete circular or oval areas of nonscarring alopecia. This form of alopecia has several clinical variants, including alopecia totalis, alopecia universalis, and an ophiasis pattern. Therapy is often difficult. The…
Actinomycosis Many species of the bacterial genus Actinomyces are able to cause disease in humans. The infection tends to run a chronic course that leads to suppurative granulomatous abscesses in the skin. The diagnosis may be suspected if there is…
Basement Membrane Zone, Hemidesmosome, and Desmosome Basement Membrane Zone The basement membrane zone (BMZ) of the epidermis is a beautiful and complex structure and a marvel of biological engineering. The zone acts to attach the overlying epidermis to the underlying…
Acanthosis Nigricans Acanthosis nigricans is a commonly encountered skin dermatosis that can be seen in various clinical scenarios. It is overwhelmingly associated with obesity but can occur secondary to medications, endocrine disorders such as the HAIR-AN syndrome ( h yper…
Adnexal Carcinoma Adnexal carcinomas are a diverse group of malignant skin tumors that are derived from the various components of the skin appendageal structures. These tumors are extremely rare and comprise well less than 1% of all skin cancers diagnosed…
Acrochordon Acrochordons are better known by their common name of skin tag or fibroepithelial polyp. They are found universally throughout humankind. Probably every adult has at least one skin tag located somewhere across the surface of his or her skin.…
Embryology of the Skin The human skin develops from two special embryonic tissues, the ectoderm and the mesoderm. Epidermal tissue is derived from the embryonic ectoderm. The dermis and subcutaneous tissue are derived from the embryonic mesoderm. The developmental interactions…