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Varicella zoster virus
Poxvirus (Smallpox and Molluscum contagiosum)
Herpes simplex virus
Malassezia (Tinea versicolor and Seborrhoeic dermatitis)
Pediculus humanus and Phthirus pubis (Lice)
Sarcoptes scabiei (Scabies)
Human herpesvirus 6 (Roseola)
Varicella zoster virus
Human herpesvirus 8 (Kaposi sarcoma)
Pigmentation skin disorders: Pathology review
Acneiform skin disorders: Pathology review
Papulosquamous and inflammatory skin disorders: Pathology review
Vesiculobullous and desquamating skin disorders: Pathology review
Skin cancer: Pathology review
Bacterial and viral skin infections: Pathology review
Viral exanthems of childhood: Pathology review
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Sam Gillespie, BSc
Kara Lukasiewicz, PhD, MScBMC
Tanner Marshall, MS
Samantha McBundy, MFA, CMI
With acne vulgaris, acne means “eruption” and vulgaris, means “common”. So acne vulgaris is a common skin eruption that occurs when hair follicles, or pores, get blocked by particles like dead skin cells or oil. Once hair follicles are blocked, it forms small raised, red bumps on the skin. Acne is particularly common among teenagers because of the skin changes that occur during puberty. Acne can be categorized into different types based on specific characteristics. For example, mild acne usually consists of whiteheads and blackheads, moderate acne, usually consists of pustules, and severe acne, usually consists of cysts and nodules.
Now, the skin is divided into three main layers--the epidermis, dermis, and hypodermis. The epidermis forms the thin outermost layer of skin, and has 5 sublayers: the stratum corneum as the outermost layer followed by the stratum granulosum, the stratum spinosum, and the stratum basale. In the palms and feet, which are areas with thicker skin, there is a fifth layer called the stratum lucidum which is around one cell layer thick. Underneath the layers of the epidermis is the dermis, and it’s mainly made up of connective tissue but also contains nerve endings, hair follicles, sweat glands, sebaceous glands, lymphatic vessels and blood vessels. Focusing on the hair follicles, each one contains a strand of hair, composed of the shaft, root, and bulb that sits in the follicle. The hair follicle is epidermal tissue that dips down into the dermis, and is associated with other structures like apocrine glands, sebaceous glands, the arrector pili muscle, and nerve receptors. Now, sebaceous glands, or oil glands, are located in the dermis layer of the skin and are connected to hair follicles. Each sebaceous glands secrete an oily substance called sebum into a nearby hair follicle or through pores that extend directly to the skin surface. Sebum is a substance made of different fatty acids and waxy esters to help transport nutrients and lubricate the skin. As it turns out, arrector pili muscles surround the sebaceous glands, so when these tiny muscles contract, sebum gets squeezed out. Sebum softens the hair shaft preventing it from becoming brittle. Sebum also prevents moisture loss from the skin and is slightly acidic, which helps to deter pathogens. And below all of this is the hypodermis which is made of fat and connective tissue that anchors the skin to the underlying muscle.
Acne vulgaris (commonly called acne) is a chronic skin disease that occurs when hair follicles are clogged with dead skin cells and oil from the skin. It is characterized by blackheads or whiteheads, pimples, oily skin, and possible scarring.
It primarily affects areas of the skin with a high number of oil glands, such as the face, chest, shoulders, and back. Acne is self-limiting but can cause significant emotional distress.
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