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Figure 3-12 Sensory stimulus on the skin.
Skin lesions
Skin lesions are fairly common but can look different in regard to shape, color, and texture. The most common skin lesions include:
•Macule – Typically called freckles, a macule can also be a flat mole, or non-palpable such as rubella.
•Plaque – Common with psoriasis, a plaque lesion defines a lesion that is slightly elevated though flat-topped, rough, and has a firm surface.
•Nodule – Most often palpable, elevated, and firm, typically one to two cm in diameter.
•Scale – This type of skin lesion is defined as keratinized cells of regular shape (thick or thin) and often silvery-white in color. These lesions often present with flaky exfoliation such as with psoriasis or exfoliative dermatitis.
•Papule – An elevated lesion that is firm yet palpable, and typically measures less than 1 cm in diameter, such as a wart.
•Wheal – This type of lesion is often irregular shaped, elevated, and can be solid or transient with variable diameters. It’s typical with insect bites or urticaria.
•Crust – A lesion that is slightly elevated, composed of dried blood, serum, or other type of exudate, commonly seen in scab formation or conditions such as eczema.
Figure 3-13 Bacteria attach to skin.
Skin lesions can also be defined in a manner that is dependent upon their appearance. For example:
•Discreet – this type of lesion is distinct in size, shape, and spacing.
•Confluence – a group of lesions merged together. Example, urticaria.
•Linear – appear as a stripe, streak, or distinct line.
•Grouped – the lesions form into clusters that are grouped in a specific area. Example: contact dermatitis.
•Gyrate – this type of lesion looks like a snake or a worm.
•Polycyclic – this type of lesion has distinct rounded edges that are closely grouped to one another.
Figure 3-14 Dermatitis and normal skin.
Some skin problems are inherited, while others are due to inadequate diet or nutritional deficiencies. Others are caused by environmental conditions. Some are caused by disorders of the immune system.
■Common Causes of Skin Problems
A number of factors can contribute to common skin problems. Various forms of fungal bacterial and viral infections are common triggers. These can typically be described based on their pathophysiology. For example, see the lists of common skin infections and their classifications listed below:
Viral
•Herpes simplex
•Herpes zoster
•Warts
Acne
•Acne vulgaris
•Acne rosacea
Eczematous
•Contact dermatitis
•Atopic dermatitis
•Lichens simplex chronicus
•Seborrheic dermatitis
Fungal infections
•Candidiasis
•Tinea (tinea corporis/tinea cruris)
Bacterial infection
•Folliculitis
•Impetigo
•Boils (furuncles)
•Carbuncle
Figure 3-15 Sunbathing and skin damage.
More serious threats, but less common, are traumatic injury or disease to the skin, including cancers and burns.
Common skin threats
According to the American Academy of Dermatology, skin cancer is rated as a leading cause of cancer in the US, with estimations that one in five Americans has a likelihood of developing some type of skin cancer during their lifetime.19
Incident rates of skin cancer, types of skin cancer, survival rates, mortality rates, and risk factors have increased globally, with nearly 10,000 Americans diagnosed with skin cancer daily.20
One of the most prevalent contributory causes of skin cancer is overexposure to sunlight or UV radiation.
Most cancers are caused by mutations of DNA in skin cells. Three major types of skin cancer are most prevalently diagnosed:
•Basal cell carcinoma
•Squamous cell carcinoma
•Melanoma
The major cause of overexposure? Tanning.
Basal cell carcinoma is the most common form of skin cancer and the least malignant. Basal cell carcinoma typically appears on areas of the skin constantly exposed to sunlight, such as the face. It’s a slow-growing carcinoma, and in many cases, metastasizes before it’s even been noticed by the individual. The good news is that through surgical excision, a person has a 99% chance of cure.21
The second most common type of skin cancer is called squamous cell carcinoma. This type of cancer grows rapidly and will metastasize if not removed in a timely manner. In general, when caught early and removed through surgical excision or radiation therapy, prognosis is good.
Melanoma, otherwise known as cancer of the melanocytes, is the most dangerous and the most resistant to chemo-therapy. Melanoma is extremely metastatic. While not as common as basal cell or squamous cell carcinoma, it can prove deadly.
Figure 3-16 Tanning and skin cancer risk.
Most of us are (or should be) familiar with the ABCDs for recognizing a melanoma growth, which often starts out looking like a freckle or a mole. As a refresher:
•Asymmetry – one of the most recognizable signs of a melanoma is asymmetry, or a
