Case Outline
A 54-year-old woman recently presented in clinic with a flat red lesion measuring 20 mm by 15 mm (maximum) on the plantar surface of her left lateral heel (figure 1). The lesion, according to the patient, had been there for as long as she could remember. On examination, the area was flat and pink/purple in colour:
Figure 1: View of left heel
Most interesting was the dermoscopy which can be seen below in figure 2. Close examination of the image revealed a pink dotted pattern located in the ridges of the skin (parallel ridge pattern, or PRP):
Figure 2: Dermatoscopic Image showing parallel ridge pattern
Diagnosis: Port Wine Stain (PWS)
Discussion
Vascular birthmarks affect around 30% of newborn children and can be classified according to which vessel is affected (capillary, lymphatic or venous). Many lesions are benign and transient, fading with time. Capillary malformations or port wine stains are the most observed type and usually present from birth as an homogenous pink or purple macule located anywhere on the skin (or mucosal surface). The condition is said to affect around 1-3 in 1000 neonates with an equal sex preponderance. The lesion consists of the dilation of normal skin capillaries in the upper dermis forming pink or purple colouration of the lesion with geographic borders. The foot is an uncommon location for PWS, more typically they occur on the face and neck, and occasionally the limbs. Despite most being congenital lesions, some have been reported appearing after localised trauma with one case reported on the sole of the foot after prolonged walking (1).
Discovery of a single lesion does not generally warrant further investigation, but multiple lesions present on the skin can suggest syndromic forms of the disease (2). Klippel-Trenaunay syndrome for example, is a condition which presents with cutaneous capillary malformations, venous disease and bony or soft tissue hypertrophy. Some capillary malformations may fade with time while others become more prominent, with a darker purple in colour, but they rarely completely disappear.
Dermoscopy
For those who use the dermatoscope for assessment of skin lesions, you will be well aware that in a pigmented (melanocytic) lesions the PRP pattern is a strong predictor for melanoma with 99% specificity (3). However, the pattern has been observed in benign conditions such as port wine stains. The pink colour of the lesion in this case pointed towards a lesion with a purely vascular aetiology of a capillary malformation. In a melanoma, the PRP arises as malignant melanocytes cluster around the sweat duct in the basal layer, vertically aligned with the ridges of the dermatoglyphics, giving rise to the observed pattern. In port wine stain, the pink colour is due to the presence increased density of capillaries in the dermis, which are unaffected in pattern by the overlying epidermis.
Treatment
For most patients, small or lesions which are not visible, reassurance is all that is required - as in this case. Extensive or lesions which are located on visible areas like the face can be treated using Pulse Dye Laser. Tuned at a wavelength around 585-600 nm, emitted photons selectively target the red pigment haemoglobin and destroys the cutaneous vasculature leaving the surrounding structures relatively spared (known as selective photothermolysis). Ultimately, treatment leads to vascular remodelling and reduction in the redness of the lesion (4). The treatment works best on lesions treated in the young and where the skin is thinner (5).
Full consent was given by the patient for the publication of the case and images.
References
1. Moriuchi R, Kikuchi K, Ito T, Shimizu S. Acquired plantar port-wine stain showing a red parallel ridge pattern under dermoscopy. Clin Exp Dermatol. 2014;39(8):944-5.
2. Diociaiuti A, Paolantonio G, Zama M, Alaggio R, Carnevale C, Conforti A, et al. Vascular Birthmarks as a Clue for Complex and Syndromic Vascular Anomalies. Front Pediatr. 2021;9:730393-.
3. Saida T, Miyazaki A, Oguchi S, Ishihara Y, Yamazaki Y, Murase S, et al. Significance of dermoscopic patterns in detecting malignant melanoma on acral volar skin: results of a multicenter study in Japan. Arch Dermatol. 2004;140(10):1233-8.
4. Brightman LA, Geronemus RG, Reddy KK. Laser treatment of port-wine stains. Clinical, cosmetic and investigational dermatology. 2015;8:27-33.
5. Ashinoff R, Geronemus RG. Flashlamp-pumped pulsed dye laser for port-wine stains in infancy: earlier versus later treatment. J Am Acad Dermatol. 1991;24(3):467-72.