Skin Conditions Quiz: Common Skin Diseases

Shingles, also known as herpes zoster, is a cutaneous recurrence of a latent viral (in spinal or cranial nerve ganglia) infection caused by the varicella-zoster or chickenpox virus. It appears as multiple vesicles in the cutaneous distribution of a sensory nerve, a dermatomal distribution. In older individuals, it can be intensely painful, producing a chronic postherpetic neuralgia syndrome.

Ringworm is caused by certain mold-like fungi on the surface of the skin. Lesions are most often well circumscribed and round. The border of the lesion may be scaly or have small blisters. Lesions are often quite itchy. The diagnosis is easily confirmed by visualization of fungal elements in the skin scales after exposure to potassium hydroxide under the light microscope.

Psoriasis characteristically appears as elevated plaques of red scaling itching skin on the scalp, elbows, and knees. Its presence aside from its unpleasant appearance signals a systemic form of inflammation that can produce a destructive form of arthritis along with premature coronary vascular disease.

Rosacea is an inflammatory condition most often characterized by pustules, papules, and redness affecting the face. The papules and pustules respond to the anti-inflammatory effect of certain antibiotics. Some patients with rosacea note an increase in the size of their nose along with an unsightly change in shape.

A boil is an acute abscess most often produced by a bacteria like Staphylococcus aureus. It probably begins as an infection of a hair follicle and then progresses to a furuncle and then an abscess. Aside from taking an appropriate antibiotic, the abscess will resolve rapidly if it is incised and drained to allow the release of pus. It appears as a rapidly enlarging, tender, red fluid-filled mass that is exquisitely painful.

Scabies is an infestation produced by a mite, Sarcoptes scabiei, which seems to have a unique predisposition to infect only human skin. After an incubation period of about three weeks, the patient develops an allergic contact dermatitis to the mite and forms very itchy red vesicles that seem to be most common in the webs of the fingers and in the groin. People often acquire the infection during sexual activity or in nursing homes.

Plantar warts are benign tumors on the sole of the foot. The human papillomavirus (HPV) causes plantar warts. They usually appear as thickened callus-like lesions with small black dots visible in their depths. If the wart is present in a weight-bearing site, like the ball of the foot or heel, they can produce significant pain. Paring the thickened skin down to the normal thickness may relieve the pain. The appearance of these warts is quite different from those on the hands, which may be due to that fact that plantar warts form on a weight-bearing surface.

Athlete''s foot is a nonspecific term given to an itchy, chronic dermatitis affecting the feet. A fungal infection often causes athlete''s foot, but it may also be a manifestation of a variety of other conditions. If it is caused by a fungus, tinea pedis is an appropriate designation. The fungal nature of the eruption can be confirmed by examining a potassium hydroxide mount of scale or skin obtained from the affected skin.

A skin tag (acrochordon) is a fleshy polyp composed of skin, fibrous tissue, and blood vessels. It is characteristically found on the neck, armpit, and inguinal (groin) creases of most adult humans at one time or another. When the blood supply at the base of the polyp becomes compromised, there may be pain associated with the tag as it dies. There is no particular medical reason to destroy these, but this is easily accomplished by freezing the skin tag with liquid nitrogen. On the other hand, patients have been known to tie a piece of thread around the base of the tag to shut off its blood supply.

The three most common forms of skin cancers are basal cell carcinoma, squamous cell carcinoma, and malignant melanoma. Most cases of these three cancers are induced by mutations caused by ultraviolet light exposure although there are a few cases of skin cancers that are inherited. They typically appear on sun-exposed surfaces. Basal cell carcinomas are pearly, reflective lesions that bleed easily. Squamous cell carcinomas are keratotic nodules. Malignant melanomas are asymmetrical, irregularly shaped pigmented tumors. Pathological examination is required for diagnosis.

Rocky Mountain spotted fever is a bacterial disease caused by R. rickettsii, which is transmitted, to humans by the bite of a hard-shelled tick. Infected patients have a high fever, a severe headache and a rash composed of fine red spots on the arms and legs. There may be no history of a tick bite. The mortality rate can be quite high unless the patient is treated with doxycycline.

Head lice or pediculosis capitis is an infestation of the scalp hair by a six-legged insect of the genus Pediculus. The major manifestation is severe itching of the scalp and neck. Simple examination often reveals these insects, but it may be necessary to examine the hair shaft for nits if the adult louse cannot be seen.

Allergic contact dermatitis is a delayed hypersensitivity reaction. The dermatitis is weepy and oozing in a distribution localized to the skin that was exposed to the allergen. The identity of the allergen can be determined through patch testing, which is a localized exposure of a known concentration of the presumed allergen under occlusion for 48 hours. Paraphenylenediamine is a dye substance used to enhance the appearance of temporary tattoos, which are known to be allergenic.

Melasma is due to the abnormal deposition of melanin pigment in facial skin. It is most common in females on the forehead, malar cheeks, upper lip, and chin. It seems to be associated with pregnancy and oral contraceptives. It is believed that light plays a role in its appearance. Treatment may require the application of a topical bleaching cream containing hydroquinone, tretinoin, or azelaic acid. Occasionally, certain laser treatments may be of benefit.

Melanomas are malignant tumor of melanocytes. Most melanomas appear as irregular, asymmetrically pigmented spots and tumors on sun-exposed skin. They may be confused with benign nevi (moles) on occasion, but their growth and asymmetry are distinctive. Since they metastasize very early, it is important to diagnose them early because the cure rate is quite high if they are less than 1 mm thick.