Acral pseudolymphomatous angiokeratoma of children: immunohistochemical and clonal analyses of the infiltrating cells

Background: Acral pseudolymphomatous angiokeratoma of children (APACHE) is a disorder characterized clinically by red nodules and histopathologically by a massive subepidermal lymphohistiocytic infiltrate. Although it was initially thought to be a vascular nevus, it has never been regarded as a pseudolymphoma. Case report: We report a 7‐year‐old‐girl with small red nodules on the dorsum of the right foot and a 73‐year‐old man with asymptomatic brown‐red nodules on the lower extremities. Results: Histopathologic examination revealed a massive lymphohistiocytic infiltrate with plasma cells, some eosinophils, or a multinucleated giant cell immediately beneath the epidermis. Thick‐walled vessels were observed in the infiltrate. These characteristics are identical to those of acral pseudolymphomatous angiokeratoma of children. The infiltrate was composed mainly of equal numbers of CD4+ or CD8+ T cells and equal numbers of B cells stained for κ or λ light chains. PCR amplification of rearranged immunoglobulin heavy chain genes or T‐cell receptor γ genes showed no evidence of clonality, suggesting that these infiltrates were polyclonal both for B and T cells. Conclusions: Our data support the idea that this disorder represents a reactive process. The modified term ‘papular angiolymphoid hyperplasia’ would define this disorder more appropriately.