Angiokeratoma circumscriptum is a cutaneous lesion of dark red or reddish blue color. It is a benign vascular disorder that doesn't require any special treatment, but is usually resected for cosmetic reasons and because malignancies may be misdiagnosed as angiokeratomas.
AC may be present at birth or develop at a later point in time . Patients more often present with unilateral, solitary lesions than with bilateral disease or multiple AC. Besides cutaneous alterations as described below, the vast majority of AC patients remains asymptomatic. However, they may claim tenderness  .
AC are usually of dark red or reddish blue color, much like hematomas, but are raised above the skin surface. They are prone to bleed, and intradermal hemorrhages may cause the lesion to change color rapidly. AC appear as well-demarcated papules or plaques that frequently have irregular borders and a verrucous surface. In the case of multiple lesions, band-like patterns, and linear arrangements prevail. Most commonly, AC affect the distal portions of either lower limb, the thighs or buttocks. However, these angiokeratomas may develop virtually anywhere. Additionally, AC of the tongue and buccal mucosa have repeatedly been described .
It is of utmost importance to distinguish AC from malignant melanoma and other skin tumors  . Histopathological analyses of biopsy specimens may strongly support the clinical diagnosis. Characteristic findings are :
- Hyperkeratosis (orthokeratosis or parakeratosis)
- Thin-walled, dilated capillaries in the papillary dermis
- Occasionally, vascular alterations comprise the reticular dermis
- Thrombosis of ecstatic vessels
AC have been shown to stain positive for lymphatic markers such as podoplanin and Prox1 .
Additional studies, namely biochemical and molecular biological analyses, may be indicated to rule out Fabry disease .
Angiokeratomas are benign cutaneous lesions characterized by ectasia of papillary dermis vessels and secondary epidermal changes like hyperkeratosis . It is important to note that they are not neoplasms . Patients may present with solitary or multiple angiokeratomas that develop in distinct parts of the skin, differ in size and surface appearance. Accordingly, the following subtypes are distinguished  :
- Angiokeratoma circumscriptum (AC), either solitary or arranged in a band-like pattern, most commonly affecting the legs
- Angiokeratoma corporis diffusum, multiple pinpoint lesions seen in patients suffering from Fabry disease, a lysosomal storage disorder 
- Angiokeratoma of Mibelli with acral localization
- Angiokeratoma of Fordyce affecting scrotum, penis or vulva 
- Solitary or multiple angiokeratomas
AC is the least common type of angiokeratoma and may be associated with Klippel-Trenaunay-Weber syndrome, Cobb syndrome, and other vascular malformations. Women are affected significantly more often than men. Contrary to untreated Fabry disease and malignancies of the skin, this disease follows a benign course and treatment is generally not required. The latter does not apply, however, if doubts remain as to the nature of the papule or plaque, or if patients request therapy for cosmetic reasons. Treatment may comprise the surgical excision of the respective lesions, but this approach may not be feasible in case of extensive AC. Laser therapy is increasingly applied in those cases.
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