Angiokeratomas are a group of vascular ectasias that involve the papillary dermis and may produce papillomatosis, acanthosis, and hyperkeratosis of the epidermis. Several clinical variants of angiokeratomas exist; angiokeratoma circumscriptum is a specific type and is the rarest of the other types of angiokeratomas. Overall, eight types of angiokeratomas have been described in the literature. Some groups of angiokeratomas are deemed to be more alarming than others. The first reported case dates back to 1889 when Doctor Vittorio Mibelli recorded what is now known as angiokeratoma Mibelli-type on the fingers and the toes. Doctor Johann Fabry first described angiokeratoma circumscriptum in 1915 as a localized lesion on a lower extremity or the trunk. In addition, a rare manifestation of angiokeratoma circumscriptum naeviforme, with appearance on the neck, has been documented. As few as only 100 cases of angiokeratoma circumscriptum have been worldwide until 2006. Angiokeratoma lesions are of clinical importance because, often being dark purple or black, they may clinically mimic a malignant melanoma. [1, 2]
In many cases, angiokeratoma lesions are present at birth, but they may also appear in childhood or adulthood. Angiokeratoma circumscriptum has been reported to coexist with angiokeratoma of Fordyce  (found on the scrotum) and caviar spots (angiokeratomas of the tongue).  Other clinical associations include its occurrence with Cobb syndrome, Klippel-Trenaunay syndrome, nevus flammeus, cavernous hemangiomas, hemangiectatic hypertrophy,  angiokeratoma corporis diffusum,  and traumatic arteriovenous fistulas. Angiokeratoma circumscriptum has also been called angiokeratoma corporis naeviform and may be best classified as a type of capillary malformation. [7, 8]
Noted by Imperial and Helwig in 1967, angiokeratomas are actually telangiectasias of already-existing vessels rather than angiomas.  How angiokeratoma circumscriptum develops has not yet been elucidated. A few proposed ideas include congenital development, pregnancy, trauma, subcutaneous hematomas, and tissue asphyxia.
Interestingly, lymphangioma circumscriptum, an entity that is microscopically similar to angiokeratoma circumscriptum, has been reported to occur in a setting of damaged deep lymphatic vessels. Unlike angiokeratoma of Mibelli or angiokeratoma corporis diffusum (Fabry disease), no pattern of inheritance or associated enzyme defect has been found for angiokeratoma circumscriptum. Overall, altered hemodynamics (typically caused by trauma) appear to produce telangiectatic vessels of the papillary dermis with an overlying reactive hyperkeratosis to the epidermis. 
The frequency of angiokeratoma circumscriptum in the United States is unknown, yet it has been reported worldwide to occur in 16% of the population. However, the condition is probably more common than what the relatively few cases in the literature indicate. Because it has no associated systemic morbidity, most cases remain clinically innocuous and go unreported. The majority of the population to develop angiokeratoma circumscriptum are males; however, it occurs in females as well. 
No ethnic predilection has been observed or reported to date.
Males are affected more commonly than females.
Angiokeratoma circumscriptum may be either congenital or acquired. Lesions are commonly present at birth, but development in early childhood and adulthood has been documented.
Angiokeratoma circumscriptum lesions are asymptomatic benign vascular malformations that require no treatment. Laser ablation has proven highly effective and may offer the best cosmetic outcome.
Angiokeratoma circumscriptum is a benign vessel ectasia involving the papillary dermis. No deaths from this entity have been reported. However, because it may clinically mimic a melanoma, morbidity may arise from attempts to render treatment for a melanoma before histologic verification is given. Furthermore, because angiokeratomata are vascular lesions, recurrent bleeding can occur. Life-threatening bleeding is not a concern because the affected vascular spaces are small. However, excessive bleeding has been noted when trauma occurs to the lesions.