Angiokeratoma

The angiokeratomas are a group of benign vascular neoplasms in which marked dilated, thin-walled vessels are situated beneath  hyperplastic and hyperkeratotic epidermis. 

The Quiz case is an Solitary Angikeratoma, which described by Imperial and Helwig¹ in 1967, this type of AK is a single small, bluish black, warty papule which occurs predominantly on the lower extremities (Quiz case is located on the shoulder). It is not a hereditary lesions and probably follows trauma, which subsequent telangiectasia prior to formation of the AK (telangiectasia also present in this Quiz case). The mode of acquiring this lesions, the small size, its solitary nature, and its location distinguish it from the other forms of angikeratoma. It should be differentiate from sbeorrheic keratosis, melanoma, pigmented basal cell carcinoma, pyogen granuloma and ordinary hemangima

There are several clinical types of angiokeratoma, 

In solitary AK, there is well-circumscribed dark red, scaly papule of at least 0.5 mm diameter, which is often found on the leg.

Multiple lesions of similar appearance can sometimes occur. Thrombosis of superficial vessels of an AK cause the lesion to appear black, simulating melanoma.

AK of Mibelli largely occurs as small multiple lesions on the skin of the dorsal toes (and sometimes fingers) in patients with cold intolerance and sometimes, perniosis.

AK of Fordyce affects scrotal or vulvar skin and, sometimes, that of the adjacent abdomen or thigh. This also features multiple lesions.

AK corporis diffusum is a component of several metabolic diseases, including Fabry’s disease (X-linked recessive alfa-galactosidase, A deficiency disease that results in ceramide trihesidose accumulation in several organs).

AK circusmscriptum is a rare condition in which a solitary plaque composed of continuous papular AK occupies a large area of skin.

Histopathology:

Sections of all of the various AK shows a combination of thin-walled, ectatic vascular space that contain erythrocytes and epidermal hyperplasia with compact hyperkeratosis.

Differential Dg:

Thrombosed Aks are often so dark in color that they are suspected of being melanoma. AK of Mebelli can sometimes be difficult to distinguish from cryoglobulinemia or perniosis, but its lesions are more sharply circumscribed. The epidermal changes of AK histologically resemble those of verrucous hemangioma, a congenital lesion in which vessels are present throughout the thickness of the dermis.

Treatment:

Solitary AK are cured by simple excision. Multiple angiokeratoma can be excised, frozen, electrodesiccated, or treated with laser.

Refrences:

1.     Imerial R et al: Angiokeratoma. Arch dermatol 1967,95:166.