Angioma serpiginosum (AS) is a rare, naevoid skin disorder with benign vascular proliferation characterized by non-purpuric violaceous to red punctate lesions on an erythematous base.
The classical pinpoint puncta are caused by either congenital hyperplasia or ectasia of pre-existing superficial dermal capillaries. Hutchinson first described angioma serpiginosum in 1889 as a peculiar form of serpiginous angioma and later coined as “infective” nevoid disease. Radcliffe-Crocker proposed the term "angioma serpiginosum" in 1893.
Most cases are sporadic. However, both autosomal dominant and X-linked dominant inheritance has been recorded. Isolated cases reports have suggested a Xp11.23 deletion containing PORCN to be one of the possible causes of angioma serpiginosum. However, this was later contradicted by some other workers. The view that angioma serpiginosum represents a mild form of focal dermal hypoplasia (FDH), which can be associated with PORCN gene mutations, has also been opposed by later reports.
Females are almost exclusively affected than males with a sex ratio of 9:1. Its prevalence is reported to be less than 1:1000000. Typically, it starts in early childhood with 80% of cases occurring before the age of 20 years. It might be present at birth. There is no racial predilection reported for this condition.
Angioma serpiginosum evolves from the proliferation of endothelial cells and formation of new capillaries and not merely by dilation of pre-existing capillaries.
Electron microscopy shows the thickening of the capillary walls caused by a heavy precipitate of basement membrane-like material intermixed with thin collagen fibers and an increased number of pericytes and some authors consider angioma serpiginosum as a type 1 mosaicism.
Researchers have disproved the role of hormones in its pathogenesis by vascular endothelial proliferation because of the lack of estrogen and progesterone receptors on the associated blood vessels. Another proposed etiology is an abnormal vascular response to cold which results in the formation and collection of newly formed capillaries that leads to large ectatic vessels in the papillary dermis.
Angioma serpiginosum is a benign vascular condition characterized by pinpoint violaceous to coppery-red punctate maculopapular eruptions that cluster together in linear, serpiginous or gyrate patterns on an erythematous background, chiefly on the lower limbs in females. It starts as one or more small asymptomatic lesions that coalesce and enlarge by developing new lesions at the periphery with central clearing, and this leads to serpiginous or gyrate or annular patterns.
They are typically asymptomatic without any bleeding or inflammation. It is predominantly seen on the lower limbs and rarely can be extensive. Lesions occurring on the upper limb, face, and neck have also been reported. Palms, soles, and mucous membranes are usually not involved, although there are a few isolated reports of involvement of acral areas. Involvement of the trunk is also rare but has been reported. The lesions usually follow the Blaschko lines. The growth is slow and irregular, and it may sometimes evolve over months to years. Exclusion of purpura from the differential diagnosis is important to prevent unnecessary investigations.
Course and Prognosis
After an initial period of growth, the lesions usually stop growing at puberty and remains stable during adulthood They may at times spontaneously resolve partially sometimes resulting in atrophy. It seldom is associated with complications and ocular and nervous system involvement association has been reported.
Rare presentations include familial cases, late onset, and extensive cutaneous involvement. Rare associations associated with angioma serpiginosum include vulval angiokeratomas, oesophageal papillomatosis, overlying cherry angioma, and retinal vein occlusion.
The common differential diagnoses to be considered include capillary haemangioma, angiokeratomas, pigmented purpuric dermatoses, and unilateral nevoid telangiectasia.
Diascopy commonly reveals non-blanchable to partially blanchable lesions. Diascopy may not be consistent within the same lesions some areas may show blanching while others may not.
Dermoscopy shows well-demarcated oval to round red lagoons due to dilated vascular spaces within the papillary or superficial reticular dermis. The dermoscopy findings in angioma serpiginosum have been described as “school of red fish in a pond.” Dermoscopy might especially be helpful distinguishing angioma serpiginosum from purpuric dermatoses.
Skin biopsy shows that the affected papillae are distended by a large single ectatic capillary, lined by flattened endothelial cells of normal appearance. There is an absence of erythrocyte extravasation, hemosiderin deposits or inflammatory cells which help differentiate angioma serpiginosum from its mimics.
Imaging studies are not usually done and are indicated only if atypical findings are present.
Reflectance confocal microscopy has been used in the diagnosis of angioma serpiginosum. Reflectance confocal microscopy also shows the multiple dilated vascular spaces in the superficial dermis, arranged perpendicular to the epidermis with a deeper vascular plexus which is arranged parallel to the epidermal surface.
Electron microscopy findings include thickening of the capillary walls which is caused by a heavy precipitate of basement membrane-like material mixed with thin collagen fibers and an increased number of concentrically arranged pericytes. The dilated capillaries may also show slit-like protrusions of their lumina and endothelial lining into the surrounding thickened vessel walls.
Angioma serpiginosum is benign and asymptomatic but can be severely disfiguring and cause significant psychological distress to the patient. Spontaneous involution may occur but is usually never complete. Treatment is indicated only for cosmetic reasons. Cosmetic camouflage is an effective option. No other topical treatment has been found to be effective in angioma serpiginosum. The treatment of choice is considered to be vascular lasers. Various lasers have been found to be effective in treating angioma serpiginosum including Argon laser, tunable pulsed dye laser (PDL), and intense pulsed light (IPL). The PDL has been the most reported laser used in angioma serpiginosum. One to seven sessions is required. Recently, 532 nm potassium titanyl phosphate laser has shown good results. The longer pulse duration of KTP laser is also related to the lower incidence of adverse effects like purpura, which is an advantage over PDL. The advantage of PDL over KTP would be the ability to penetrate deeper; although, significant depth of penetration is not required for most cases of angioma serpiginosum. KTP lasers also have a smaller beam size as compared to the PDL. Also, KTP is absorbed by melanin (other than hemoglobin/oxyhemoglobin) and therefore requires higher fluences, especially with darker skin. This might be associated with higher incidence of adverse effects.