| Popis: |
Hair erector muscle (HEM) is everywhere in dermatopathology but has been less studied than other smooth muscle systems in the skin. HEM disorders are passive and active, the former related to the involvement, as a bystander fascicle, by nearby conditions. The muscle can be permeated by nevus cells, infiltrated or destroyed by keratoacanthoma and other malignancies, encroached by hemangiomas, suffused by erythrocytes in purpura and pyocytes in an abscess, incorporated into scars and entrapped and deformed by a dermatofibroma. Less passively, HEM can participate in follicular processes, insect bites, collagen-vascular diseases, syphilis, solar elastosis and amyloid. More proper to the muscle yet rarely encountered are myositis (dermatomyositis), poorly understood myopathies (atrophy, vacuolar changes, eosinophilic globules), deposit diseases (glycogenosis) and, even, rare dystrophies (Duchenne/Becker). Finally, other than HEM tumors (leiomyoma, leiomyosarcoma), hamartomatous conditions include disorganized/hypertrophic muscle in blue nevi, hyperplasia in Becker’s nevus, and more substantial muscle mass increase as in smooth muscle hamartoma (including similar changes in mature port-wine stain) and in the rare congenital midline hamartoma. This presentation outlines orderly features and, mainly, compiles disorders of HEM, few of them a disease on its own but still a supplement to a gamut of many more noticeable entities. |
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