Macules are a flat, localized change in skin color. These spots represent a primary skin lesion, the initial visible sign of a change occurring within the skin. While often benign and cosmetic, macules can indicate an underlying health condition that requires medical attention.
Defining Macules and Their Visual Traits
A macule is defined as a small, circumscribed area of skin discoloration that is not raised or depressed. The defining feature is that they are non-palpable; you cannot feel any change in the skin’s texture or thickness. The medical standard for a macule is a size of less than one centimeter (1 cm) in diameter.
The color of a macule can vary significantly depending on its cause, presenting as red, brown, white, or purple. For example, a macule can be hyperpigmented, appearing darker than the surrounding skin, or hypopigmented, appearing lighter due to a lack of melanin.
Distinguishing Macules from Other Skin Lesions
In dermatology, the specific size and texture of a lesion are paramount for proper classification. Macules are differentiated from other common skin lesions based on whether they are flat and their overall size.
The most similar lesion is a patch, which shares the characteristic of being flat and non-palpable. Patches are larger macules, defined as any flat area greater than one centimeter (1 cm) in diameter. Examples include large birthmarks or the diffuse discoloration seen in conditions like vitiligo.
Other lesions are distinguished by their elevated nature, as they can be felt when touched. A papule is a small, solid, raised bump that is less than 1 cm in size, such as a typical pimple or mole. A plaque is a broader, elevated lesion, typically a flat-topped area of skin that is larger than 1 cm in diameter, often associated with conditions like psoriasis.
Common Underlying Causes
The discoloration that defines a macule arises from changes in the layers of the skin, most commonly involving pigment or blood vessels. The most frequent cause is a change in melanin, the pigment responsible for skin color. Freckles, known medically as ephelides, are classic examples of macules caused by increased local melanin production following sun exposure.
Another common category is post-inflammatory hyperpigmentation, where a darker macule is left behind after an inflammatory event like acne or an insect bite has healed. Conversely, macules can be hypopigmented, such as the white spots seen in tinea versicolor, a common fungal infection that interferes with pigment production. Conditions like vitiligo also cause white macules or patches due to the loss of melanocytes, the cells that produce pigment.
Macules can also result from vascular issues, which involve changes to the blood vessels near the skin surface. Petechiae are tiny, reddish-purple macules caused by small amounts of blood leaking from capillaries under the skin. These spots do not blanch, or turn white, when pressure is applied, which helps distinguish them from inflammatory redness. Certain vascular birthmarks, known as vascular nevi, may also present as reddish or purplish macules due to an abnormal collection of blood vessels.
When to Seek Professional Evaluation
While many macules are harmless, professional evaluation is warranted if a spot exhibits specific changes. Warning signs relate to a rapid change in the lesion’s appearance. This includes a sudden increase in size, an irregular or blurred border, or a dramatic shift in color toward shades of black, blue, or multiple hues.
Any macule that begins to develop new symptoms should also be examined by a healthcare provider. These concerning symptoms include persistent itching, tenderness, bleeding, or the development of an open sore that does not heal. Furthermore, the sudden appearance of multiple new macules across the body could signal a systemic illness or widespread rash and requires prompt diagnosis.