Purple lesions are spots, patches, or bumps on the skin or mucous membranes that look violet, bluish, or dusky red. Most fall into one of two groups: bleeding under the skin (such as petechiae, purpura, and bruises), or a growth or inflammation of blood vessels and skin tissue (such as vascular birthmarks, lichen planus, or Kaposi sarcoma). A simple press test, the pattern of the spots, and a few blood tests usually point to the cause, and treatment is aimed at that cause rather than at the color itself.
In my practice, patients often arrive worried about a new purple patch. Many causes are harmless, but some signal a blood or vessel problem that needs prompt attention. This guide explains how clinicians sort them out.
What Counts as a Purple Lesion?
“Purple lesion” is a description, not a diagnosis. The color comes from blood, either leaked out of vessels into the skin or held inside abnormal or inflamed vessels. Lesions can be flat or raised, single or many, painful, itchy, or completely silent. Many people notice them only by chance, a reminder that no symptoms does not always mean nothing is wrong.
The first clinical question is whether the spot blanches. Pressing a clear glass or slide on it (called diascopy) tells you whether blood is still inside vessels (the color fades) or has escaped into the tissue (the color stays).
| Lesion type | Size / appearance | Blanches? | Usual meaning |
|---|---|---|---|
| Petechiae | Pinpoint dots, under about 3 mm | No | Low or poorly working platelets, raised vein pressure, infection |
| Purpura | About 3 mm to 1 cm | No | Platelet, clotting, or vessel-wall problem |
| Ecchymosis (bruise) | Larger than 1 cm | No | Trauma, fragile skin, clotting problem, blood thinners |
| Palpable purpura | Raised, can be felt | No | Inflammation of small vessels (vasculitis) |
| Vascular lesions | Flat or raised, often stable | Often yes, at least partly | Birthmarks, venous lakes, angiomas |
Common Causes of Purple Lesions
Blood and Platelet Causes
Many purple lesions have hematologic causes. Platelet disorders are the classic example: when platelets are too few or do not work properly, tiny vessels leak and petechiae or purpura appear, often on the lower legs first. Causes include immune thrombocytopenia (ITP), bone marrow disease, leukemia, and certain medicines.
Clotting-factor problems, such as hemophilia, liver disease, vitamin K deficiency, or anticoagulant drugs, tend to cause larger bruises and deeper bleeding rather than pinpoint spots.
Vessel-Wall and Skin Causes
- Senile (actinic) purpura: flat purple patches on the forearms and backs of the hands in older adults, due to thin, sun-damaged skin.
- Steroid purpura: similar fragility from long-term corticosteroid use.
- Vasculitis: inflamed small vessels cause raised, palpable purpura; IgA vasculitis is a common form in children.
- Scurvy: vitamin C deficiency weakens vessel walls, causing bleeding around hair follicles and gums.
Non-Bleeding Causes
Some purple lesions are not bleeds at all. Venous lakes, port-wine stains, and angiomas are vascular growths. Lichen planus produces itchy, flat-topped violet bumps. Kaposi sarcoma, a vascular tumor most often seen with weakened immunity, forms purple patches or nodules. Skin cancers such as melanoma can occasionally look purple or dark, which is why an unexplained changing lesion needs a proper look.
How Purple Lesions Are Diagnosed
Diagnosis starts with a history and examination. I ask when the lesions appeared, whether they followed an injury, which medicines and supplements the person takes (including aspirin, anti-inflammatories, and blood thinners), and whether there is bleeding elsewhere, such as from the gums or nose, or in the urine. The distribution, size, and whether lesions are raised all help narrow the list.
Common tests include:
- Complete blood count (CBC): checks the platelet count, normally about 150,000–450,000 per microliter, along with red and white cells.
- Blood smear: looks for abnormal cells or clumped platelets.
- Coagulation tests: PT/INR and aPTT screen the clotting cascade.
- Kidney function and urine test: important when vasculitis is suspected.
- Skin biopsy: confirms vasculitis, lichen planus, Kaposi sarcoma, or other skin conditions.
- Dermoscopy: a magnified skin exam that helps separate vascular and pigmented lesions.
Treatment Options
Treatment depends entirely on the cause. For bleeding problems, the aim is to correct the platelet count or the clotting defect. That may mean stopping or adjusting a medicine, treating ITP with corticosteroids or other immune therapies, replacing vitamin K or a missing clotting factor, or investigating the bone marrow.
Vasculitis is managed by treating any trigger and, when organs are involved, with anti-inflammatory or immunosuppressive drugs. Lichen planus usually responds to topical steroids. Kaposi sarcoma is treated by restoring immune function where possible, sometimes with local or systemic cancer treatment. Harmless vascular lesions can be left alone or treated with laser for cosmetic reasons.
For senile purpura, protecting the skin from knocks and sun, and moisturizing, is often all that is needed. The patches fade over a couple of weeks, though new ones may appear.
Complications and Prevention
The lesion itself is rarely the danger; the underlying condition is. A very low platelet count can lead to bleeding inside the body, including, rarely, into the brain. Untreated vasculitis can damage the kidneys, and ongoing blood loss can cause iron deficiency anemia. Fragile-skin purpura can tear and ulcerate, especially on the shins of older adults.
Prevention depends on the cause, but a few habits help most people:
- Protect thin skin with long sleeves and sunscreen, and pad sharp furniture edges at home.
- Review medicines and supplements that affect bleeding with your doctor or pharmacist, especially if you take more than one.
- Eat a varied diet with fruit and vegetables for vitamin C and leafy greens for vitamin K.
- Keep regular follow-up if you already have a known platelet, clotting, or autoimmune condition.
When to See a Doctor
Arrange a medical review for any purple lesion that is new and unexplained, spreading, changing shape or color, or not fading after two to three weeks. Seek urgent care if:
- Non-blanching spots appear with fever or feeling very unwell, which can signal serious infection such as meningococcal disease.
- You have widespread petechiae, blood blisters in the mouth, or bleeding from the gums, nose, or in the urine or stool.
- Raised purpura come with abdominal pain, joint pain, or blood in the urine.
- Bruising is heavy and you take a blood thinner.
For more on how platelets affect bruising and bleeding, see our platelets guide.
Frequently Asked Questions
Are purple lesions always serious?
No. Many are harmless, such as senile purpura or small bruises from knocks you did not notice. The concern is lesions that appear without explanation, keep multiplying, or come with bleeding, fever, or feeling unwell.
What is the difference between a bruise and purpura?
Both are blood under the skin. A bruise usually follows injury and is larger than 1 cm, while purpura are smaller spots that often appear without trauma and may reflect a platelet or vessel problem.
Can medications cause purple lesions?
Yes. Aspirin, anti-inflammatory painkillers, anticoagulants, some antidepressants, and long-term corticosteroids can all make purple spots or bruises more likely. Do not stop a prescribed medicine on your own; discuss it with your doctor first.
Which blood test checks for purple spots?
The complete blood count is the first test, because it measures platelets. Clotting tests such as PT and aPTT are usually added, and further tests depend on those results.
