Persistent cutaneous pseudolymphoma after intradermal gold injection.

After intradermal testing with goldsodiumthiomalate (GSTM), 5 out of 8 patients developed skin papules at the test sites, which persisted up to 20 months. The lesions were surgically excised. Histology revealed pseudolymphoma of B and T cell type containing follicular structures and occasional small granulomas. The amount of histiocytic cells among B and T lymphocytes was pronounced, including acid cysteine proteinase inhibitor (ACPI) positive follicular dendritic cells, CD68 positive macrophages, factor XIIIa positive dermal dendrocytes and S-100 positive cells. By electron microscopy, the macrophages contained endosomes loaded with crystalloid material which contained gold in X-ray microanalysis. Atomic absorption spectrophotometry also confirmed the presence of gold in one specimen. Thus GSTM seemed to accumulate in tissue macrophages leading to constant immunologic activation with lymphoid proliferation and histiocytic response.