A marble-like red pattern on the legs in SLE: livedo reticularis, vasculitis, or a light-triggered rash?

When to call 1669, and when to be seen the same day

A net-like pattern on the legs, without other warning signs, is not a reason to call 1669.

The NHS stroke symptoms page, opened 31 October 2026, says to call emergency services if you think you are having or have had a stroke, or if signs appeared within the last 24 hours even if they have stopped. Sudden signs on that page include face weakness, trouble smiling, arm weakness or numbness, and slurred or confused speech. Other signs listed there are weakness or numbness down one side, blurred vision or loss of sight in one or both eyes, trouble finding words, confusion or memory loss, dizziness or falling, a severe headache, and nausea or vomiting. In Thailand that call is 1669 when the person is not already in a hospital. Do not drive there.

The NHS pulmonary embolism page, opened the same day, says to call emergency services for sudden difficulty breathing, pain in the chest or upper back, a very fast heartbeat, or someone passing out. Coughing up blood is on that page’s urgent-appointment list, not the emergency-call list. Pain and swelling in a leg, usually the calf, with skin that is red, blue, or darker, are described there as deep-vein thrombosis and can be harder to see on brown or black skin. That needs an urgent visit, not 1669, unless one of the emergency items is also present.

An ulcer, black skin, tissue death, or a digit that is very cold and pale needs a same-day clinician visit, following the Johns Hopkins descriptions of untreated cutaneous vasculitis and of tissue loss in Raynaud phenomenon. Fever with new palpable purpura is also a same-day concern. If the person is already in a hospital, tell the staff there.

Short answer

A net-like pattern on the legs in SLE can be livedo reticularis. That pattern is not antiphospholipid syndrome, not vasculitis, and not a UV rash. Hot air is not the same as ultraviolet light. Do not start aspirin from the pattern alone.

A photo does not name the pattern

A net or marble-like pattern can suggest livedo reticularis. One photo does not name the subtype, and it does not show whether antiphospholipid antibodies are present. The page on an itchy rash when SLE is suspected and the page on an elbow rash that burns and is not named as SLE answer different questions. So do the pages on leg swelling after long standing and on warning signs before another stroke.

Before the visit about a net-like rash

Photograph the pattern when it is present and when it has faded. Note heat or cold, how long it lasted, and whether there is pain, an ulcer, or swelling in one leg.

Prepare the notes before the visit about a net-like rash in SLE

Several net patterns, and they are not one name

The DermNet livedo reticularis page, updated September 2016, describes mottled skin in a net or lace, with a cyanotic colour around pale centres, blotchy and reddish-blue to purple. It can be transient or persistent, mostly affects the legs, may be more pronounced in the cold, may or may not improve with warming, and cold can cause tingling or numbness.

That page keeps the names apart. Cutis marmorata is a physiologic, changeable pattern, temporary in about 50% of healthy infants and in many adults, especially young women in the cold. It usually fades on rewarming and is usually symptomless. Primary livedo reticularis in adults is intermittent and less influenced by room temperature. Livedo racemosa is generalised and persistent, with irregular broken markings, and often involves the trunk and buttocks as well as the legs.

The DermNet SLE page, February 2015, lists livedo reticularis among nonspecific skin findings and says it occurs in 20% to 30% of patients with SLE. That is a group figure, not the chance of the person reading this page, and not the risk of APS.

The livedo page points the other way. It says antiphospholipid syndrome results in livedo racemosa in 25% of patients with APS, and in 70% of those with SLE-associated APS. Those are shares among people who already have APS. They are not the share of net patterns that turn out to be APS.

A net is not an antibody result, and an antibody result is not APS

The Johns Hopkins Lupus Center page on antiphospholipid antibodies, opened 31 October 2026, says many people with these antibodies have a purple or reddish lacy pattern on the arms and legs. Having the pattern does not mean the antibodies are present. The page calls it a correlation. The pattern also occurs with other vessel diseases and in many healthy women.

That page, whose listed sources stop in 2009, writes three different sentences. One: about 50% of people with lupus have these antibodies. Two: over twenty years, about half of lupus patients who have the lupus anticoagulant will have a blood clot. Three: 50% of people with lupus have APS. All three are group statements on that page. None is the chance for a person with a net pattern today, and none is the 20% to 30% livedo figure.

The same page lists fetal loss or miscarriage, clots in veins or arteries, low platelets from immune attack, stroke, transient ischemic attacks, a clot on a heart valve, pulmonary emboli, and pulmonary hypertension. It says clotting risk does not necessarily follow lupus activity. Antibodies named there include the lupus anticoagulant, anticardiolipin, and anti-beta-2 glycoprotein I. Levels can rise and fall.

The APS wording on that page is a different tool from the 2023 criteria. The page says complications from the antibodies, together with clots or pregnancy complications and a significant antibody level, usually indicate APS.

The 2023 ACR/EULAR APS classification criteria, published October 2023, are for research. They are not a home score from a photograph. Entry requires at least one positive antiphospholipid antibody test within 3 years of an antibody-associated clinical criterion. Classification then needs at least 3 points from the clinical domains and at least 3 points from the laboratory domains. The six clinical domains are large-vein thrombosis, large-artery thrombosis, microvascular disease, obstetric disease, heart-valve disease, and hematologic disease. The two laboratory domains are lupus anticoagulant coagulation assays and ELISA for IgG or IgM anticardiolipin and/or IgG or IgM anti-beta-2 glycoprotein I. The abstract gives a range of 1 to 7 points per item. It does not assign points to livedo. In the validation cohort, specificity was 99% versus 86% for the 2006 revised Sapporo criteria, and sensitivity was 84% versus 99%. Those pairs describe the criteria in a research cohort. They are not the reader’s chance.

The DermNet livedo page says extensive screening is unlikely to help without a careful history and examination, and that a lupus anticoagulant panel should be ordered in acquired livedo that is not brought on by cold. That is a clinician decision for that pattern. It is not a home panel for every net that fades with temperature, and it is not a rule to test nobody. A history of clots, stroke, repeated pregnancy loss, and a low platelet count belongs in the visit. The page on SLE with a pulmonary embolism is for someone who already has a known lung clot. There is no English twin of that page.

Vasculitis, vessel occlusion, and a net are different

The DermNet SLE page calls cutaneous vasculitis palpable purpura or urticarial vasculitis, and it calls vasculopathy at the digit tips occlusion of small vessels by thrombus. Those are separate lines.

The Johns Hopkins skin page describes cutaneous vasculitis as inflammation of vessels near the skin that restricts flow. Lesions may look like hives, may itch, and do not turn white when pressed. Digits may develop tissue death. Untreated lesions may ulcerate and necrose.

The livedo page separates the microscope pictures. Early vasculopathy shows lymphocytes and histiocytes on the vessel wall, joining fibrin and closing capillaries. Neutrophilic vasculitis of medium vessels is a different picture. A net alone is not called vasculitis on this page. An ulcer or black skin needs a prompt visit, because both vasculitis and the livedoid vasculopathy mentioned on that page can involve ulcers.

Ultraviolet light, heat, and Raynaud phenomenon

Johns Hopkins says about 50% of people with lupus are sensitive to sunlight and other ultraviolet sources, including artificial light, both UV-A and UV-B. That is a group figure. DermNet says lupus-specific rashes tend to be induced or worsened by ultraviolet radiation and sit on sun-exposed skin such as the face, neck, upper chest, and upper back. Photoprovocation uses ultraviolet or visible wavelengths. The Lupus Foundation of America page, updated 8 February 2024 and medically reviewed 9 January 2023, says ultraviolet rays in sunlight and some indoor lights can worsen rashes and other lupus symptoms. Hot air is not in those definitions.

Specific rashes are acute, subacute, or chronic. The subacute form may be ring-shaped or scaly. The Lupus Foundation says about one in three cases of that form is due to, or made worse by, common medicines such as proton-pump inhibitors or some calcium-channel blockers, and that this can appear months to years later. That is a different rash from a net. Do not stop a medicine because of this page.

The same foundation says a new rash in lupus can be a drug reaction, an allergy, or another skin disease such as eczema or psoriasis. Treatment needs the right name first. It points to a dermatologist who knows lupus, working with a rheumatologist when there is one. On darker skin, red or pink may look dark purple or dark brown.

The NHS heat-rash page, reviewed 9 May 2024, next review due 9 May 2027, describes small raised spots 2 mm to 4 mm across, some fluid-filled, with an itchy or prickly feeling and mild swelling. Blocked sweat glands are the cause, and it usually settles in a few days. A net is not that rash.

DermNet calls erythema ab igne a one-sided form of livedo from local heat injury. Ask whether heat was applied to one area. Do not use the name heat rash for a net.

Johns Hopkins separates Raynaud phenomenon, present in about one third of people with lupus, a group figure. Fingers or toes blanch, then turn blue, then red, in cold that other people might find only mildly uncomfortable. Ulcers and tissue death of the digits can follow. Cigarettes and caffeine can make it worse. A clinician may consider a calcium-channel blocker to widen vessels. That is a treatment for Raynaud phenomenon, not a cause of the net, and not an instruction to start a medicine. A net can look stronger in the cold, but the drawing is not the three-colour change of the digits.

Biopsy, medicines, and smoking

DermNet says that if a biopsy is required, at least two samples should come from the red-blue area and the white area, with serial sections. A palpable site is preferable. Even a large biopsy from the centre of a livedo racemosa ring may be reported as normal. More than one sample raises the chance of seeing a medium vessel in the deep dermis and fat. This page does not send everyone for a biopsy.

There is no specific treatment for the pattern except avoiding cold. Rewarming, or treatment of a known cause, may let the colour return. When occlusive vasculopathy is confirmed, DermNet says a clinician may recommend low-dose aspirin and anticoagulants. The SLE page says aspirin is recommended for diagnosed APS. Neither sentence is an instruction to buy a medicine because of a net. Do not start aspirin or a blood thinner, and do not stop a lupus medicine.

The livedo page says smoking cessation is essential to reduce arterial events such as stroke. The SLE page says, in a separate sentence, that smoking is linked with more severe disease and with weaker antimalarial effect. Medicines named on the livedo page include amantadine, minocycline, gemcitabine, catecholamines, and nonsteroidal anti-inflammatory drugs. Bring the start dates. Do not stop them from this page.

Net, vasculitis, ultraviolet rash, and sweat rash

Point	Livedo	Vasculitis	Ultraviolet rash	Sweat rash
What the opened sources describe	A reddish-blue to purple net, mostly on the legs	Palpable purpura, or hive-like lesions that do not blanch, sometimes with ulcers	A lupus-specific rash induced by ultraviolet light, usually on sun-exposed skin	Small raised spots, 2 mm to 4 mm, itchy or prickly
What raises that possibility	Change with cold, or a broken pattern that stays	Pain, an ulcer, or black skin	It follows sun or ultraviolet light, not hot air alone	Heavy sweating, then spots within a few days
What this page does not order	No APS name from the net	Not every net is vasculitis	Hot air is not photosensitivity	Do not call a net a sweat rash

What a clue can suggest, and what it cannot settle

Clue	What it can suggest	What it cannot settle
A red-purple net	Livedo reticularis	The cause
It fades when warmed	Cutis marmorata is possible	Other diseases are not cleared
A broken pattern that stays	Livedo racemosa	A cause still has to be sought
A net plus APS antibodies	Vessel risk is higher in that context	APS still needs clinical and laboratory criteria
Palpable purpura	Vasculitis is possible	Further tests may be needed, and a biopsy is not for everyone
Ulcer or black skin	Vasculopathy or vasculitis	Same-day care
A rash on sun-exposed skin	Photosensitivity or cutaneous lupus	It is not always a net
Spots after sweating	A sweat rash is possible	The spots have to match, not a net
A net plus swelling in one leg	A clot has to be considered	Urgent assessment
A net plus sudden neurologic signs	Stroke has to be considered	Call 1669 if not already in a hospital

Questions to answer for the clinician

When did the pattern start?
Does it appear only in hot weather?
Has it appeared in the cold?
How many minutes or hours until it fades?
Are both sides equal?
Is there pain, burning, numbness, or itch?
Is there palpable purpura?
Is there an ulcer or black skin?
Are the toes cold or pale?
Is one leg swollen?
Do the digits change through white, blue, and red?
Has there been a clot in a leg or a lung?
Has there been a stroke or a warning spell?
Have there been repeated pregnancy losses or other pregnancy complications?
Have antiphospholipid antibodies been tested?
What was the lupus anticoagulant, if tested?
What was anticardiolipin, if tested?
What was anti-beta-2 glycoprotein I, if tested?
What is the platelet count?
Is the lupus active or quiet now?
What are C3 and C4, if measured?
What is anti-dsDNA, if measured?
Is there urine protein or kidney inflammation?
Which immune-suppressing medicines are in use?
Does the person smoke?
Is an estrogen-containing contraceptive or hormone therapy in use, so clot risk can be reviewed?
Should dermatology or rheumatology come first this time?
Is there a reason for an antiphospholipid panel?
Is there a reason for a biopsy, and from which site?
Which symptoms mean the emergency department before the next visit?

What to bring

A photo while the pattern is up, and a photo when the skin is closer to its usual colour
Start time, how long it lasted, and whether it followed heat, cold, or sun
Pain, numbness, ulcers, and leg swelling
Clot history, stroke history, and pregnancy history
Every medicine, including lupus medicines, with start dates
Earlier APS results, if any
Blood count and platelets, complement, and anti-dsDNA
Urine, protein, and kidney function, if measured
Smoking history

Mechanism, as summarized by the author

Asst. Prof. Dr. Norawit Raatpiboon lines the opened sources up this way. The net appears when skin blood flow falls and deoxygenated haemoglobin increases. At the edge of each vascular unit the capillary bed is thinner than at the centre. Cold can spasm small arteries and the colour can return. Prolonged spasm, clot, or thick blood fits a pattern that stays. Lupus-specific rashes follow a different path, tied to ultraviolet light rather than the temperature of the air. The net is a vessel sign. It is not the name APS, and it is not the name vasculitis.

Sources opened for this page

Common questions

Can SLE cause a net-like pattern on the legs?

Yes. The DermNet SLE page from February 2015 reports livedo reticularis in 20% to 30% of patients with SLE. That is a group figure, not the chance of the person reading this page, and not the risk of APS.

What is livedo reticularis?

DermNet describes a net or lace, reddish-blue to purple, around pale centres, mostly on the legs, transient or persistent.

Is this pattern dangerous?

DermNet says the pattern itself is relatively benign. An associated clotting disease such as APS can lead to serious arterial events. The pattern alone does not show that disease.

How is livedo different from vasculitis?

A net is not vasculitis. DermNet separates vessel occlusion from neutrophilic vasculitis of medium vessels, and the SLE page calls cutaneous vasculitis palpable purpura or urticarial vasculitis.

How is livedo different from Raynaud phenomenon?

Johns Hopkins describes Raynaud phenomenon as fingers that turn white, then blue, then red in the cold. Livedo is a net on the limbs that may look stronger in the cold. They are not the same name.

How is livedo different from a light-triggered rash?

Lupus-specific rashes are tied to ultraviolet light and usually sit on sun-exposed skin. A net is not that rash.

Is hot weather the same as photosensitivity?

No. Johns Hopkins and the Lupus Foundation tie photosensitivity to ultraviolet light, not to air temperature.

What does a sweat rash look like?

The NHS page reviewed 9 May 2024 describes small raised spots 2 mm to 4 mm across, itchy or prickly, sometimes fluid-filled, from blocked sweat. That is not a net.

How does the pattern relate to APS?

Johns Hopkins says many people with antiphospholipid antibodies have livedo. Having the pattern does not mean the antibodies are present, and antibodies plus a net are not the name APS by themselves.

Does everyone with the pattern need antibody tests?

No. DermNet says broad screening without a history and examination is unlikely to help, and that a lupus anticoagulant panel should be ordered when livedo is acquired and not brought on by cold. A clinician decides.

Can the 2023 APS criteria be applied to the pattern alone?

No. Those criteria classify people for research. They need an antibody result within 3 years of a clinical criterion, then at least 3 clinical points and at least 3 laboratory points. The abstract does not give points for the pattern alone.

What if there is an ulcer or black skin?

See a clinician the same day. Johns Hopkins says untreated cutaneous vasculitis may ulcerate and cause tissue death.

What if one leg is swollen as well?

The NHS pulmonary embolism page describes pain and swelling in a leg as a deep-vein thrombosis. That needs an urgent visit. If breathing becomes suddenly difficult, the chest hurts, or someone passes out, and the person is not already in a hospital, call 1669.

Is aspirin or a blood thinner needed?

Do not start either. DermNet says low-dose aspirin and anticoagulants may be recommended once occlusive vasculopathy is confirmed, or for diagnosed APS.

Should lupus medicines be stopped?

No. The Lupus Foundation says a new rash may come from a medicine or from another skin disease, and treatment needs the right name first.

How should the photos be taken?

Take one while the pattern is up and one when it has faded. Note heat or cold, how long it lasted, whether both sides match, and whether it hurts.

Dermatology or rheumatology?

The Lupus Foundation points to a dermatologist who knows lupus and who works with a rheumatologist when there is one. This page does not rank who must come first for every person.

Which symptoms mean calling 1669?

Call when the person is not already in a hospital and has a sign on the NHS emergency lists for stroke or for pulmonary embolism. The pattern alone is not that call.

If the pattern fades with warmth, is it safe?

Cutis marmorata usually fades on rewarming. Primary livedo in adults is less tied to temperature, and livedo racemosa can persist. Fading alone does not clear other diseases.

Can local heat cause a net?

Yes. DermNet calls erythema ab igne a one-sided livedo from local heat injury. Ask whether heat was applied to that area.

Limit of this page

This page summarizes sources that were opened, so a reader can prepare questions. It does not name a disease from a photo, and it does not say to start aspirin, start a blood thinner, or stop a lupus medicine. If an emergency sign is present and the person is not already in a hospital, call 1669.