Dermatology Library

P

PABA:

Short for para-aminobenzoic acid. It is used in many sunscreens. It works well, but some people are allergic to it. If you're allergic to PABA, use a PABA-free sunscreen instead.

Papillomavirus (Human Papillomavirus):

See: Warts

Papules:

Pink bumps on the skin.

Pediculosis:

See: Head Lice

Pemphigus vulgaris:

Pemphigus vulgaris (PV) is one of a group of chronic, relapsing auto-immune diseases causing blistering of the skin and mucosal membranes. Substances called antibodies produced by the immune system normally attack hostile viruses and bacteria. In a person with pemphigus, the immune system mistakenly regards the cells in skin and mucous membranes as foreign, and attacks them. This causes burn-like lesions or blisters that do not heal. Pemphigus vulgaris is very rare. There is no cure but it is controllable with heavy immunosuppressive treatment. It is non-infectious.

Perioral Dermatitis:

Perioral dermatitis is a common skin problem that affects young women and occasionally, men or children. "Perioral" refers to the area around the mouth, and “dermatitis” indicates a rash or irritation of the skin. The areas most affected by perioral dermatitis are the facial lines from the nose to the sides and borders of the lips, and the chin. The areas around the nose, eyes, and cheeks can also be affected. There are small red bumps, mild peeling, mild itching, and sometimes burning associated with perioral dermatitis. When the bumps are the most obvious feature, the disease can look like acne.

Phlebectomy:

A treatment for varicose veins. The enlarged vein is removed through tiny incisions made along its length. The procedure is called ambulatory phlebectomy when it is performed in an outpatient facility and the patient goes home the same day.

Also see: Veins

Photoaging/Photodamage:

Photodamage may be chronic or acute; acute photodamage is a sunburn. Photoaging and photodamage (dermatoheliosis) are terms used interchangeably to describe those chronic changes in the appearance and function of the skin caused by repeated sun exposure rather than by the passage of time (the latter called intrinsic or chronologic aging). Overwhelming epidemiologic and laboratory evidence indicates that sun exposure and other sources of UV radiation (UVR) play the major role in causing the undesirable skin changes of fine and coarse wrinkles, roughness, laxity, mottled pigmentation, actinic lentigines, actinic keratoses, leathery texture/coarseness, scaling/xerosis, sallowness, and telangiectasia. Cigarette smoking is the only other environmental factor that has been related to the development of changes in the skin associated with aging. Because there is equally compelling evidence that UVR, from sun exposure or artificial sources, or both, is associated with an increased incidence of benign, premalignant, and malignant skin neoplasms, the changes of photoaging/photodamage have important epidemiologic significance, as well as aesthetic implications and are therefore not trivial concerns. No credible scientific evidence contradicts the relation of sun exposure to the development of skin cancer and the undesirable results of photoaging and photodamage.

Phototherapy:

Phototherapy is exposure to nonionizing radiation for therapeutic benefit. It may involve exposure to UVB, UVA or various combinations of UVB and UVA radiation. Photochemotherapy (PUVA) is the therapeutic use of radiation in combination with a photosensitizing chemical. It currently involves the use of psoralens and UVA radiation. Treatment with these modalities may involve partial or whole-body exposure.

Piedra:

Piedra is a fungous infection of the hair shaft, caused by either Piedraia hortae (black piedra) or Trichosporon beigelii (white piedra).

Also see: Fungal Infections

Piercing:

See: Tattoos and Piercing

Pityriasis rosea:

Pityriasis rosea is a rash that occurs most commonly in people between the ages of 10 and 35, but may occur at any age. The typical rash begins with a single lesion - known as a herald patch (also called primary plaque of mother patch) - that heralds the onset of a more generalized rash that comes after a variable period of time. One to two weeks after the appearance of the herald patch, the secondary rash appears in crops. Appearance of the secondary rash may rarely be delayed for 2 to 3 months or they may appear almost simultaneously. The lesions usually have a central distribution, on the trunk and proximal limbs. The secondary rash has a Christmas-tree-like pattern. Usually there are no permanent marks as a result of this condition, although some darker-skinned persons may develop long-lasting flat brown spots that eventually fade. It may occur at anytime of year, but pityriasis rosea is most common in the spring and fall. Pityriasis rosea usually does not itch and is not contagious.

Pityriasis versicolor:

Pityriasis (tinea) versicolor is a superficial infection of the stratum corneum by the yeast Malassezia furfur (syn. Pityrosporum orbiculare). This yeast is part of the normal cutaneous flora. Pityriasis (tinea) versicolor is characterized by hyperpigmented and hypopigmented scaly patches, primarily on the trunk and proximal extremities. It is a common disorder that affects people of all age groups, but is most commonly seen in adults. Infants and children can also be affected, but often have an atypical presentation. This disease is typically worse in geographic areas with tropical ambient temperatures. Multiple factors are known to contribute to its pathogenesis.

Also see: Tinea

Plantar warts:

See: Warts

Plaque psoriasis:

Psoriasis characterized by red, silvery-white, scaly skin lesions (most common variety of psoriasis).

Also see: Psoriasis

Precursor lesion:

A lesion that has the potential to develop into a melanoma. Precursor lesions include dysplastic nevi, benign compound nevi, small and large congenital nevomelanocytic nevi, and lentigo maligna.

Also see: Melanoma

Primary cutaneous melanoma:

Any primary melanoma lesion, regardless of tumor thickness, in patients without clinical or histological evidence of regional or distant metastatic disease.

Also see: Melanoma, Skin Cancer

Pruritus:

A sensation that provokes the desire to scratch. Itching can be a significant source of frustration and discomfort for patients. When severe, it can lead to loss of sleep, anxiety, and depression.

Psoriasis:

Psoriasis is a chronic skin disease that is classically characterized by thickened, red areas of skin covered with silvery scales. The extent of skin involvement can range from discrete, localized areas to generalized body involvement. The joints, nails, and mucous membranes may also be affected with the disease. Some cases of psoriasis are so mild that people don’t know they have it. Severe psoriasis may cover large areas of the body. Dermatologists can help even the most severe cases. Psoriasis is not contagious and cannot be passed from one person to another, but it is most likely to occur in members of the same family. In the United States, two out of every hundred people have psoriasis (four to five million people). There are approximately 150,000 new cases that occur each year.

Psoriatic Arthritis:

A genetically driven autoimmune disease that occurs in less than 10% of persons with psoriasis. Large and small joints are affected. Psoriatic arthritis is often associated with psoriasis in fingernails and toenails.

Pseudoxanthoma elasticum (PXE):

A rare, inherited disease that affects selected connective tissue in some parts of the body. Its incidence has been estimated at 1/25,000-50,000. However, the true incidence is unknown, as it is likely that some patients are so mildly involved that they escape diagnosis and some have atypical presentations. Elastic tissue in the body becomes mineralized, that is, calcium and other minerals are deposited in the tissue. This can result in changes in the skin, eyes, cardiovascular system and gastrointestinal system. Skin changes are sometimes the first indication that a person has pseudoxanthoma elasticum . The affected individual might notice small bumps, or lesions, on the skin. Typically, these skin changes appear first on the sides of the neck and then progress to other parts of the body, but other sites may be involved. The skin lesions are asymptomatic. They do not cause any problems in and of themselves. The definitive tool to diagnose the disorder is a skin biopsy done by a dermatologist.

Pustule:

An inflammatory comedo that resembles a whitehead with a ring of redness around it. A pus-filled pimple.

PUVA:

The acronym for Psoralen + ultraviolet light A. PUVA is a type of phototherapy used in treatment of psoriasis. Treatment requires the patient to ingest, topically apply, or bathe in a medication called psoralen before being exposed to UVA rays.

See: Psoriasis

PXE:

See: Pseudoxanthoma elasticum