Diseases and Disorders of the Skin
The skin can provide physicians with clues about the health of the body, since many diseases that affect other organ systems are evident as telltale clues on the skin. A rash, such as that typical of measles or chicken pox, can indicate an infection that affects the whole body. Yellow tinge of the skin signals that the liver is not working properly. Other diseases are specific to the skin itself. These disorders range from the merely distressing to the potentially life-threatening.
Acne occurs when a hair follicle becomes blocked, usually by keratin-containing dead cells, preventing sebum from reaching the surface of the skin. Bacteria that normally live in the hair follicle break down the sebum behind the blockage, producing chemicals that cause inflammation in the surrounding skin. The result of this inflammation is a pimple. Acne tends to occur during the teenage years because hormones that increase at puberty promote both keratin formation and sebum production.
Staphylococcus aureus is commonly found in boils, carbuncles, and pimples. It also causes impetigo, a skin disease that usually affects children and is characterized by small blisters containing pus that easily rupture and form a thick, yellowish crust. Streptococcus pyogenes causes erysipelas, which are red patches in the skin. Burns, is a skin disease characterize by blue-green pus, are often infected by pseudmonas aeruginosa.
Bedsores or Pressure Sores
Bedsores or pressure sores, also known as decubitus ulcers, develop in patients who are immobile (bedridden or confined to a wheelchair). The weight of the body, especially in areas over bony projections such as the heels and hip bones, compresses tissues and causes reduced circulation. The consequence is destruction of the hypodermis and deeper tissues that is followed by death of the skin. Once the skin dies, microorganisms gain entry to produce an infected ulcer.
Birthmarks are congenital disorders of the capillaries in the dermis of the skin. A strawberry birthmark is a mass of soft, elevated tissue that appears bright red to deep purple in color. In 70% of patients, strawberry birthmarks disappear spontaneously by the age of seven. Port-wine stains appear flat, bluish or dull red patches that persist throughout life.
Eczema and Hives
In response to various triggering substances, or allergens, immune cells known as mast cells in the skin may release a chemical called histamine. Other immune cells called T-cells may directly damage the epidermis. These can result in either of two skin disorders, eczema or hives. Eczema is a red, scaly rash that commonly occurs in body folds such as in front of the elbow, behind the knee, and around the groin. Hives (also called urticaria) are red, raised, weltlike lesions on the skin, often occurring on the face and neck. Hives are often triggered by ingestion or inhalation of a substance, such as a medication or food, to which a person is allergic. Occasionally, hives may be an indication of a more serious, even life-threatening allergic reaction. In such situations, the airways can become constricted, making breathing difficult.
Ringworm is a fungal infection that affects the keratinized portion of the skin, hair, and nails and produces patchy scaling and an inflammatory response. Several species of fungus cause ringworm in human are described by their location on the body; in the scalp the condition is ring worm, in the feet it is athlete's foot, and in the groin, it is jock itch.
An elevation of the skin that is variable in size and is often pigmented and hairy is called a mole. It is an aggregation of melanocytes in the epidermis. Most people have 10 to 20 moles which appear in childhood and enlarge until which appear in childhood and enlarge until puberty.
Any type of cell present in the skin can become cancerous. Two types of cancers of keratinocytes, squamous cell carcinoma and basal cell carcinoma are together the most commonly diagnosed cancers. These cancers can usually be cured by surgical removal. A far more dangerous cancer is melanoma, a cancer that develops from melanocytes. When diagnosed early, it can often be surgically cured, but this form of cancer may spread rapidly, or metastasize, to the internal organs and can be fatal within months of diagnosis.
All of these types of skin cancer are related to sun exposure. Scientists believe that the sun's ultraviolet rays damage the DNA of the skin cells, eventually turning them cancerous. Skin cancer develops most commonly on sun-exposed areas, such as the face, hands, arms, and legs. People who have light skin that sunburns easily are at higher risk of skin cancer, as are people who have a history of significant sun exposure, particularly those who regularly sunbathe or those who work outside without protective clothing, such as lifeguards. However, several decades may elapse between sun exposure and the development of skin cancer - someone who was a lifeguard at age 20 may not develop skin cancer until age 50, for example. Moles are other darkly pigmented areas of the skin that change appearance by enlarging, bleeding, or developing irregular borders or coloring may be a sign of cancer. Doctors recommend that people at risk for skin cancer regularly self-examine their body for any skin changes. Whatever their skin tone, people can reduce their risk of developing skin cancer by wearing clothing that covers the body and a hat that shields the face when in the sun and by using a sunscreen with a sun protection factor (SPF) of 15 or greater.
Cold sores (herpes simplex), German measles, chickenpox, measles, and warts (which are caused by a viral infection of the epidermis), are some of the viral infections of the skin