What’s going on when I have spots on my body?

Author: Li Houmin, Chief Physician, Peking University People's Hospital

Reviewer: Yang Rongya, Chief Physician, Seventh Medical Center, PLA General Hospital

In daily life, we may encounter such a situation from time to time, that is, a color change occurs locally on the skin or mucous membrane. It is neither bulging nor sunken, and cannot be perceived by touch. It is just a localized color change. We call this color change a macules.

Of course, different colored rashes often represent different diseases. Let's learn more about them together.

erythema:

Erythema refers to localized redness, and the diseases involved vary due to different pathogenesis.

Some erythema is caused by infection, such as erysipelas, which is a bacterial infection. The most common sites are the lower legs or one side of the face. This type of erythema is called inflammatory erythema. Since inflammatory erythema is a symptom caused by congestion, in addition to color changes, there will also be local burning, redness, swelling, tenderness, and may be accompanied by regional lymph node enlargement and other symptoms.

Figure 1 Original copyright image, no permission to reprint

There are also some erythema that is not caused by infection. For example, some children are born with red birthmarks. This kind of birthmark cannot be felt, but only the local skin turns red. Red birthmarks are more likely to occur on the back of the scalp. The skin is red and flat to the touch. Moreover, this kind of erythema is caused by abnormal blood vessel development and will fade when pressed.

The reason for fading under pressure, such as erythema caused by vasodilation and increased blood vessels, will turn into normal skin color when pressed, but when you release your hand, it will become congested and turn into erythema again.

For example, purpura is a redness of the skin caused by bleeding. It is caused by the red blood cells running from the blood vessels to the outside of the blood vessels, so it cannot fade when pressed. Of course, this bleeding will gradually be absorbed and subside, so it has a color change, bright red at the beginning, gradually turning dark red; if the bleeding is deep, it will turn blue. Just like the place where you bump, the skin is prone to purpura. During the absorption process, it may appear blue, dark red, black, and then return to normal skin color.

Spots that are darker than your skin color:

The most common localized color deepening is post-inflammatory pigmentation. When the skin is damaged, the local skin is repaired and the melanin production increases, so the local color will deepen. Common examples include black acne marks, which are a type of post-inflammatory pigmentation. After a burn, there may also be a localized color deepening, which is also post-inflammatory pigmentation.

Some localized pigmentation is caused by complex mechanisms. For example, there is a common clinical disease called chloasma. Chloasma is a localized pigmentation that occurs on the zygomatic region and cheeks. Generally, its boundaries are not clear and the pathogenesis is very complex. It may be related to estrogen or sunlight exposure.

In addition, some liver diseases may also cause local pigmentation to darken.

Spots lighter than skin color:

If the color of this area of ​​skin is lighter than normal skin color, we call it hypopigmentation. The most common clinical case of this condition is vitiligo.

Figure 2 Original copyright image, no permission to reprint

The cause of vitiligo is very complex, and may be related to genetic factors, or to clinical triggers, such as sun exposure, emotional stress, local friction, etc. In the early stages of vitiligo, the skin color becomes lighter, and later it becomes more obvious, appearing porcelain white.

In addition to vitiligo, there are some other diseases that can also manifest as local skin color lightening, such as pityriasis versicolor. The scientific name of pityriasis versicolor is pityriasis versicolor. This kind of hypopigmentation generally appears in areas with more oil secretion. In some places, the pigment may darken. There may be some fine scales on the surface. It is a superficial fungal infection disease.

White lines:

There is a kind of white lines which are secondary rashes of the skin. They can be called growth lines or atrophy lines. Growth lines are caused by rapid growth, which pulls and breaks some fibers of the dermis, resulting in dermal atrophy. This kind of lines feels a little concave. When it first occurs, it is red. After it gets old, it slowly turns white and becomes narrower. It has such a development process.

There is another type of growth lines that occur on the abdomen during pregnancy, also called stretch marks, which also occur through the same mechanism.

In addition to stretch marks accompanied by loss or reduction of skin tissue, other diseases may also present similar symptoms. According to the location of the lost tissue, it can be divided into epidermal atrophy, dermal atrophy and subcutaneous tissue atrophy.

If atrophy occurs in the epidermis, the skin lines are reduced and appear to be refractive, similar to the reflection of parchment. If atrophy occurs in the dermis, the epidermis is completely normal, but due to the reduction of dermal tissue, the skin will be dimpled, which will be more obvious if the subcutaneous fat is atrophied.

If this skin atrophy is secondary to some other diseases, in addition to skin symptoms, the patient will also show some manifestations related to the primary disease.