The Diagnostic Process: Imaging, Bloodwork, and Biopsy

Diagnosing Sneddon syndrome is a complex process because no single blood test, biopsy, or scan can definitively “prove” the condition exists ^[1]. Instead, doctors use a combination of clinical exams, specialized imaging, and tissue samples to build a case for the diagnosis while ruling out other common stroke causes and systemic disorders. This is known as a clinical diagnosis—it relies heavily on the presence of the characteristic skin pattern (livedo racemosa) alongside evidence of cerebrovascular disease ^[1][2].

Brain Imaging: Supportive Clues

Magnetic Resonance Imaging (MRI) is essential for evaluating the brain’s blood vessels. While an early or unremarkable MRI does not automatically rule out Sneddon syndrome, doctors look for several possible supportive patterns that, when combined with your clinical history, point toward the diagnosis:

• Non-Territorial Infarcts: In a typical stroke, the damage often follows the path of one major artery (a “territory”). In Sneddon syndrome, MRIs may show scattered, small areas of damage across different parts of the brain (non-territorial infarcts) ^[3].
• Microbleeds and Siderosis: Using specialized MRI sequences, doctors may find tiny spots of old bleeding (microbleeds) or staining on the brain’s surface (superficial siderosis) ^[4]. These findings are variable and can occur in other small-vessel disorders, but they are useful pieces of the puzzle ^[4]. Importantly, if microbleeds are present, they create a treatment trade-off that your doctor must weigh when prescribing blood thinners; they do not automatically rule out anticoagulation.
• Atrophy: Over time, reduced blood flow can cause certain areas of the brain to shrink slightly, known as multifocal cerebral atrophy ^[3].

The Skin Biopsy: Searching for Clots

A skin biopsy can provide strong supportive evidence, but it must be performed carefully. Because the affected blood vessels are located deep in the skin, a standard shallow biopsy may miss the diagnosis entirely ^[5][2].

• The Technique: Dermatologists and dermatopathologists often recommend taking samples from the white center of the lace-like skin pattern. The biopsy needs to reach the deep border between the dermis and the fat layer (the subcutis) where the small arteries reside ^[5][6]. The exact number and location of samples are specialist decisions.
• Occlusive Microangiopathy: This is the term pathologists use when they see that the small arteries are blocked by thickened walls or small clots without prominent inflammation ^[5][2][7].

Because the exact biopsy approach is determined by the specialist based on the lesion, and because the blocked vessels are scattered, even a technically perfect biopsy only captures the necessary changes in a percentage of cases (roughly 70% in some standardized studies) ^[2][5]. A “normal” or negative biopsy does not mean you do not have Sneddon syndrome if your other symptoms fit the pattern ^[8].

Essential Bloodwork and Heart Testing

Beyond imaging and biopsies, your medical team will run tests to characterize your specific risk profile.

Antiphospholipid Antibody Screening

Doctors will test your blood for markers such as lupus anticoagulant, anticardiolipin antibodies, and anti-beta-2-glycoprotein-I antibodies ^[9].

• If a test is positive, your doctor may repeat it at least 12 weeks later. This repeat test is not to “confirm” Sneddon syndrome, but to establish whether you have persistent antibodies that meet the criteria for Antiphospholipid Syndrome (APS), which often carries a higher risk of future clots ^[10].
• Be aware that if you are already taking certain anticoagulants, they can interfere with lupus anticoagulant testing. This requires careful coordination with your specialist and the laboratory.

Cardiac Echocardiogram (Heart Ultrasound)

Sneddon syndrome can sometimes involve the heart valves. A baseline transthoracic echocardiogram (an ultrasound of the heart) is often appropriate during the initial diagnostic or stroke workup ^[11]. While one specific study found valve involvement in 50% of an antibody-negative cohort, the findings can be subtle and clinically variable, and this prevalence does not mean half of all patients will develop severe clinical heart disease ^[11]. The need for and timing of repeat echocardiograms will be individualized based on your symptoms and the initial results ^[12].