What Is Nailfold Capillaroscopy and Why Is It Performed?

Nailfold capillaroscopy is a non-invasive diagnostic imaging technique used to visualize and assess the small blood vessels, or capillaries, in the skin at the base of the fingernails. This area, known as the nailfold, is unique because the capillaries run parallel to the skin’s surface, allowing their entire length to be observed. The primary purpose of the examination is to evaluate the health of the microcirculation, which is the blood flow through the smallest vessels.

The Nailfold Capillaroscopy Procedure

The examination lasts between 15 and 30 minutes. To begin, the patient is seated comfortably and asked to rest for about 15 to 20 minutes in a room with a controlled temperature, between 20 and 25 degrees Celsius, to allow their circulation to stabilize. The fingers to be examined, often all except the thumbs, are then placed on a supportive surface at heart level. Thumbs are generally avoided due to the higher likelihood of capillary irregularities from daily mechanical stress.

A clinician then applies a drop of immersion oil, such as cedar or olive oil, onto the skin at the base of the nail. This oil makes the outer layer of skin more transparent and reduces light scatter, which significantly improves the visibility of the underlying capillaries. Using a specialized instrument like a videocapillaroscope or a dermatoscope, which is a type of handheld microscope with a light source, the clinician examines the nailfolds. These devices provide magnification, often around 200x, for a detailed view.

The examiner places the scope’s probe against the oiled skin and systematically moves it to capture clear images of the capillary network. The process is painless and non-invasive. Images are often captured digitally, which allows for detailed analysis, comparison over time, and documentation in the patient’s medical record.

Observing Nailfold Capillaries

During a nailfold capillaroscopy, the focus is on the structure of the capillaries. In a healthy individual, the capillaries appear as uniformly sized and shaped hairpin or U-shaped loops. These loops are arranged in neat, parallel rows along the nailfold, indicating an organized architecture. A normal capillary density is generally considered to be between 7 and 12 capillaries per millimeter.

Abnormal findings suggest damage to the microvasculature. One common abnormality is capillary loop dilation, where the capillaries become wider than normal. When a capillary becomes significantly enlarged, it is referred to as a giant capillary. The presence of even a single giant capillary can be an indicator of an underlying disease of the small blood vessels.

Other signs of abnormality include microhemorrhages, which are small spots of bleeding. Clinicians also look for a loss of capillaries, which creates avascular areas. A disorganized arrangement of the capillary network is another important finding. The formation of new, often misshapen and branched blood vessels, a process called neoangiogenesis, also points to significant vascular changes.

Clinical Relevance and Disease Association

The findings from a nailfold capillaroscopy have significant clinical relevance, especially in rheumatology. The procedure is a tool for the early detection and diagnosis of systemic autoimmune diseases that affect the microvasculature. Its most recognized application is in the evaluation of systemic sclerosis, also known as scleroderma. In these cases, a characteristic “scleroderma pattern” of abnormalities can be identified.

This examination is particularly useful for differentiating between primary and secondary Raynaud’s phenomenon. Raynaud’s phenomenon involves episodes of reduced blood flow to the fingers and toes. In its primary form, it is a benign condition, and capillaroscopy results are typically normal. However, when Raynaud’s is secondary to another condition like scleroderma, the capillaroscopy will reveal abnormalities, signaling an underlying systemic disease.

The test also provides information for other connective tissue diseases. In dermatomyositis, for instance, patients may show bushy, branched capillaries and other changes similar to the scleroderma pattern. While findings in systemic lupus erythematosus (SLE) can be more varied and less specific, they can still contribute to a comprehensive patient assessment. The pattern and severity of capillary damage can also offer prognostic information, helping to monitor disease activity and predict complications like digital ulcers.

Patient Preparation and Considerations

To ensure the best possible results, patients are advised to follow a few preparation steps.

• Avoid wearing any nail polish, gel, or artificial nails for at least one to two weeks before the examination, as these can obscure the view.
• Refrain from getting a manicure or pushing back their cuticles for several days prior to the test, because minor trauma can cause inflammation.
• Inform the clinician of any recent injuries to their hands or fingers.
• Avoid consuming caffeine or using tobacco for a few hours before the appointment, as these substances can affect blood vessels.

The test is safe, involving no radiation or significant discomfort, and is performed by a rheumatologist, dermatologist, or a specially trained technician.