Evaluation of dermal pericapillary fibrin cuffs in venous ulceration using confocal microscopy.

Dermal pericapillary fibrin is a hallmark of venous disease and is thought to play a pathogenic role in the development of ulceration. However, the actual spatial configuration of pericapillary fibrin is unknown, and it remains unclear whether it truly represents a barrier that can impair physiological exchanges between the blood and dermis. Using confocal microscopy on tissue specimens taken from the edges of venous ulcers in six patients, we report a detailed analysis of dermal pericapillary fibrin deposits. Sections were evaluated with an antibody to human fibrinogen/fibrin and viewed, vertically and horizontally, with confocal microscopy. The distribution of fibrin deposition was highly variable and patchy, with areas of great intensity next to others of marginal intensity. Vertical cut sections showed the highest concentration of fluorescent material next to the lumen of dermal capillaries. Horizontal sections showed that maximal fluorescence was distributed at random. Our findings indicate that fibrin deposits in venous ulcers are patchy and discontinuous around dermal vessels. As such, these deposits are unlikely to act as a true and stable anatomic barrier as originally proposed. However, pericapillary fibrin may still act as a physiological barrier under conditions of poor blood flow where even marginal or patchy fibrin deposition might have a greater effect on the exchange of oxygen and other nutrients between blood and dermis.