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Pseudolymphomatous angiokeratoma
Pseudolymphomatous angiokeratoma
Clinical features Pseudolymphomatous angiokeratoma (acral pseudolymphomatous angiokeratoma, APACHE) was originally described as a disorder presenting as unilateral, asymptomatic, red, angiomatous papules and nodules on acral sites of children with equal sex incidence and predilection for the hands and feet, particularly the digits.1โ3 However, similar cases have rarely been described in adults with a wider anatomic range including elsewhere on the limbs and the trunk. It is likely that the latter represent examples of T-cell rich angiomatoid polypoid pseudolymphoma (TRAPP, see below). Lesions tend to be persistent and are exceptionally linear.4โ8
Cases of cutaneous T-cell pseudolymphoma (CTPL) may be idiopathic, but many can be classified as distinct clinicopathological entities, the main ones being lymphomatoid drug eruptions, lymphomatoid contact dermatitis, pseudolymphomatous angiokeratoma (APACHE), T-cell rich angiomatoid polypoid pseudolymphoma (TRAPP), pseudolymphomatous folliculitis, chronic actinic dermatitis (CAD), persistent arthropod bite reaction, lymphomatoid keratosis, and atypical cutaneous lymphoproliferative disorder of HIV infection.1,6โ14 Several of these specific entities are discussed below, or elsewhere in this or other chapters. Many idiopathic cases show considerable overlap with primary cutaneous CD4-positive small/medium pleomorphic T-cell lymphoproliferative disorder, and may well be part of the same spectrum of disease.15,16
Pathogenesis and histologic features The etiology is unknown and there is no relation with angiolymphoid hyperplasia (epithelioid hemangioma) as has been suggested.9 The epidermis appears flattened, and there may be some degree of interface change. In the underlying dermis, there is a prominent, often diffuse infiltrate composed of lymphocytes and variable numbers of plasma cells. Cytological atypia is absent. In the background, there are numerous, small,1 thin-walled vascular channels. T cells tend to predominate with both CD4+ and CD8+ T cells represented.10,11 Rarely, B cells are prominent. Unlike other angiokeratomas,