A cyst is a closed sac of tissue that develops under the skin or inside the body, typically filled with fluid, semi-solid material, or air. While most cysts are benign and painless, the sudden appearance of a dark, purple discoloration signals a change in the underlying structure. This color shift does not automatically indicate a serious illness, but it warrants a closer look at the biological events occurring beneath the skin’s surface. A purple hue is primarily a visual sign that the cyst has experienced a significant internal event, usually involving blood or an intense inflammatory response.
The Physiological Reason for Purple Coloration
The change in a cyst’s color to purple is a direct result of changes in the blood supply and composition within or immediately surrounding the growth. The most common cause is localized hemorrhage, which is the leakage of blood from small vessels into the cyst cavity or the adjacent tissue. When this bleeding occurs, the hemoglobin in red blood cells begins to break down, mimicking the process of a common bruise.
As hemoglobin degrades, it progresses through a cycle of color changes, starting red-blue and eventually turning purple, blue, and then green-yellow before being reabsorbed. A purple cyst represents the stage where deoxygenated blood or broken-down blood pigments are visible through the skin. This effect is intensified when the pooled blood is close to the surface or when the cyst wall is thin.
Another mechanism is a severe inflammatory response, often triggered by a sudden rupture or infection. Inflammation involves the dilation of blood vessels and an increased concentration of blood flow to the affected area. This engorgement creates a dark, purplish tint, especially in a localized mass.
Increased pressure within a rapidly growing or ruptured cyst can also compress and damage surrounding blood vessels, contributing to the bluish-purple discoloration. The darkness is a visual cue that a large volume of blood or highly concentrated inflammatory cells are contained within a confined space.
Types of Cysts Associated With a Purple Appearance
Several types of benign growths exhibit this distinct purple or dark coloration, with the appearance often linked to the internal contents or structure. A common cause is a hematoma, which is not a true cyst but rather a solid swelling of clotted blood outside of blood vessels, often following trauma. This collection of blood appears dark purple or black as it pools and clots beneath the skin.
A ruptured epidermal inclusion cyst frequently presents with a purple appearance due to the intense inflammation it causes. These cysts are filled with keratin, and when the cyst wall breaks, the keratin is released into the dermis, triggering a foreign-body immune reaction. This acute inflammatory process leads to swelling, redness, and the deep purplish color associated with severe tissue irritation.
Vascular lesions, such as hemangiomas or certain venous malformations, are growths primarily composed of blood vessels and inherently appear dark or purple. A cavernous hemangioma, for example, is found in the deeper layers of the skin and has a faint blue or purple color because of the pooled blood within the abnormal vessels. Similarly, a cherry angioma can appear in various colors, including purple, due to its composition of tiny, dilated blood vessels.
Another example is a hemorrhagic ovarian cyst, which forms when a functional cyst bleeds internally after ovulation. If this internal cyst is large enough or ruptures, the resulting bleeding and irritation can cause deep pelvic pain and other systemic symptoms. The purple color is due to the blood filling the cyst cavity, though the color is not externally visible on the skin.
Accompanying Symptoms That Require Medical Attention
While a purple cyst is often the result of a benign event like a minor hemorrhage or sterile rupture, certain accompanying symptoms indicate the need for immediate medical consultation. The presence of a fever above 100.4°F suggests a systemic infection that requires prompt treatment. A cyst that is rapidly increasing in size over a few hours or days is also a warning sign, as this can indicate aggressive infection, rapid internal bleeding, or an unexpected malignancy.
Severe and escalating pain that is out of proportion to the size of the cyst should prompt medical attention, especially if accompanied by nausea or vomiting. These symptoms can signal a serious event, such as the rupture of a larger cyst or, in the case of an ovarian cyst, the complication of ovarian torsion. The presence of pus, particularly if foul-smelling, indicates a bacterial infection that requires drainage and likely antibiotic therapy.
A spreading area of redness, often described as red streaks radiating away from the cyst, is a sign of cellulitis, a potentially serious skin infection. Unexplained weakness, dizziness, or paleness along with the purple discoloration suggests internal bleeding and a loss of blood volume. These signs move the issue beyond a simple skin concern and into an area of immediate health risk.