Differences in pink, purple port wine birthmark vessel depths may influence treatment

The superficial vasculature in purple port wine birthmarks was closer to the epidermis than the vasculature in pink port wine birthmarks, which may have implications in imaging or treatment parameters, according to a study.

Joseph N. Mehrabi, MS, of the department of dermatology at the University of California, Irvine, and colleagues described port wine birthmarks as congenital capillary malformations.

“Vessel characteristics, such as diameter and depth, may impact presentation and outcomes,” they wrote.

The cross-sectional observational study included 108 patients (37% male; mean age, 32.3 years) undergoing treatment for port wine birthmarks at one of three clinical sites. The researchers classified the birthmarks by color and then obtained high-resolution, noninvasive dynamic optical coherence tomography (D-OCT) images to determine in vivo vascular characteristics as a function of the color.

Results showed a correlation between mean age and color of port wine birthmarks. The color was lighter among younger individuals and darker among older individuals (P < .01).

A shallower mean superficial plexus depth was reported among those with purple as opposed to pink birthmarks (adjusted mean difference, –39.1 µm; 95% CI, –80.9 to 2.6).

A trend toward increasing vessel diameter was observed from pink to red to purple birthmarks. However, the researchers said that this trend was not significant and that, ultimately, color carried no association with mean diameter or density of the vessels that underwent analysis.

In individuals with pink port wine birthmarks, a 10.6 µm increase in superficial plexus depth was reported for every 10-year increment in age. For those with purple birthmarks, a 16.2 µm reduction in superficial plexus depth was reported for every 10 years.

For birthmarks that underwent no previous treatment, those that were purple had a 12.7% lower vessel density than their pink counterparts (P = .02).

Limitations included the number of subjects in the study as well as previous laser treatment of some lesions, which may have influenced vascular characteristics.

“Superficial vessels of purple [port wine birthmarks] were significantly closer to the epidermis than pink [port wine birthmarks], which might impact optimal laser parameters,” the researchers wrote.