Nailfold capillaroscopy is a simple, non-invasive imaging technique used to observe the smallest blood vessels, the capillaries, in the skin fold at the base of the fingernail. This procedure utilizes specialized magnification to visualize the microcirculation, offering an immediate look at the health of the peripheral circulatory system. The test is painless and serves as a valuable tool for physicians in the early identification and monitoring of systemic diseases that affect the body’s microvasculature. Capillaroscopy helps assess the blood flow, density, and structural integrity of the capillaries in real-time.
What is Nailfold Capillaroscopy?
Nailfold capillaroscopy focuses on the capillaries located in the skin directly above the cuticle, known as the nailfold. This area is chosen because the capillary loops are arranged parallel to the skin surface, unlike in most other areas of the body where they are perpendicular. This unique orientation allows the entire length and morphology of the blood vessels to be clearly viewed under magnification.
The equipment used often includes a videocapillaroscope, considered the gold standard, or a high-magnification dermatoscope. These devices combine a microscope with a digital camera, providing magnification ranging from 50x to 600x (200x is a common setting). The magnification allows the clinician to assess capillary density, the dimension of the vessel loops, and any architectural disorganization. Immersion oil is placed on the nailfold to make the skin more translucent and improve image clarity.
The Patient Experience
The patient experience during nailfold capillaroscopy is straightforward and involves minimal preparation. Patients are asked to avoid manicures, nail polish, and trimming cuticles for approximately two weeks prior to the examination. This precaution is necessary because minor trauma can cause micro-hemorrhages and swelling, which may interfere with the accurate interpretation of the results.
To ensure the microcirculation is not constricted, patients are advised to avoid smoking and consuming caffeine for several hours before the test. The examination room is kept at a comfortable temperature (20 to 22 degrees Celsius), and the patient’s hands acclimatize for at least 15 minutes. The procedure is entirely non-invasive and painless. A handheld optical probe is gently placed on the nailfold of each finger, excluding the thumb, and images are captured, usually taking only 15 to 30 minutes to complete.
Key Diagnostic Applications
Nailfold capillaroscopy is primarily used to investigate patients presenting with Raynaud’s phenomenon, a condition causing the fingers to become pale and cold in response to stress or cold temperatures. The test is effective at differentiating between primary Raynaud’s (generally benign) and secondary Raynaud’s (associated with an underlying systemic disease). Abnormal capillary patterns signal microvascular damage, pointing toward the more serious secondary form.
The procedure is a tool in the early diagnosis and prognosis tracking of connective tissue diseases. It is relevant for systemic sclerosis (scleroderma), a chronic autoimmune disease that affects the body’s connective tissue. Capillaroscopy findings are specific enough to systemic sclerosis that they have been incorporated into the international diagnostic criteria for the disease.
Physicians use this technique to aid in the diagnosis and monitoring of other related conditions, including dermatomyositis and mixed connective tissue disease (MCTD). While specific changes are less pronounced in systemic lupus erythematosus (SLE), the test still provides valuable information about microvascular involvement. Detecting specific abnormalities early can predict the future development of a connective tissue disease in patients who initially only show symptoms of Raynaud’s phenomenon.
Interpreting Capillary Patterns
Interpretation involves a qualitative assessment of the capillaries’ morphology, density, and architecture. A normal pattern is characterized by a homogeneous arrangement of capillaries shaped like regular, inverted U-shaped hairpins, with a density of seven to twelve loops per millimeter. Capillaries in a healthy individual are uniform in size, typically having an apical width between 10 and 25 micrometers.
Pathological patterns are identified by deviations from this uniform appearance, such as the presence of “megacapillaries,” which are enlarged vessels with a diameter of 50 micrometers or more. Other signs of microvascular damage include micro-hemorrhages (small dots of bleeding) and capillary drop-out (avascular areas where capillaries have been destroyed). These specific abnormalities are characteristic of the “scleroderma pattern,” a visual finding associated with systemic sclerosis and related disorders.
The scleroderma pattern is classified into three progressive stages: early, active, and late.
Early Stage
The early pattern shows few giant capillaries and micro-hemorrhages with little loss of capillary density.
Active Stage
The active pattern includes more frequent giant capillaries and micro-hemorrhages, alongside a moderate reduction in capillary density.
Late Stage
The late stage is marked by a severe loss of capillaries, leading to extensive avascular areas. The remaining capillaries often show abnormal branching and neoangiogenesis.