Diagnosis: Angiokeratoma
An angiokeratoma is a benign pink-red to blue-black variably sized papule or plaque that is typically 2 to 10 mm in diameter.1 Angiokeratomas are composed of a series of subepidermal dilated capillaries that have a characteristic hyperkeratotic surface and bleed easily.2 These lesions are rare, with a prevalence estimated to be 0.16% in the general population.3
The pathogenesis of angiokeratoma formation is unclear; however, multiple theories exist. The development of these lesions may be related to repeated trauma or friction at a particular site.4 Alternatively, increased venous blood pressure or primary degeneration of vascular elastic tissue could explain their development.5 While their cause is unclear, the initial event in the development of an angiokeratoma is believed to be the development of a vascular ectasia within the papillary dermis. The epidermal reaction appears to be a secondary phenomenon due to increased proliferative capacity on the surface of the vessels.5
The most common form—as seen in this case—is the solitary or sporadic angiokeratoma. It comprises 70% to 83% of all cases of angiokeratomas3 and usually develops on the lower extremities. Angiokeratomas typically arise during the first 2 decades of life,6 and are more common in men.3 Other types of angiokeratomas include angiokeratoma of Mibelli, angiokeratoma of Fordyce, angiokeratoma circumscriptum, and angiokeratoma corporis diffusum (Fabry’s disease).7,8
Angiokeratoma of Mibelli is characterized by pink to dark red papules or verrucoid nodules that occur most commonly in men7 and involve the bony prominences, such as the elbows.
Fordyce lesions involve the scrotum or vulva and are usually numerous and related to conditions with elevated venous pressure.
Angiokeratoma circumscriptum usually present as papules that commonly coalesce to form plaques.
Fabry’s disease, or angiokeratoma corporis diffusum, is an X-linked recessive disease related to a deficiency in alpha-galactosidase A. This leads to multiple, variably sized angiokeratomas occurring in childhood that are concentrated between the umbilicus and the knees. This disease invariably leads to involvement of other organs, which may result in renal failure, myocardial infarction, or cerebrovascular accidents.1,7