Localized chrysiasis induced by laser therapy.

Background: Chrysiasis is a rare blue-gray skin discoloration that occurs in sun-exposed sites of some patients who receive gold salts. A unique case of localized chrysiasis developed immediately after Q-switched ruby laser (694 nm) irradiation for postinflammatory hyperpigmentation secondary to granuloma faciale in a patient who was receiving long-term gold sodium thiomalate therapy for psoriatic arthritis. Skin biopsy specimens showed striking changes in the ultrastructural characteristics of cutaneous gold deposits following laser treatment.
Observations: A blue-gray skin discoloration developed immediately after laser exposure and persisted unchanged after 1 year. Transmission electron microscopy of skin biopsy specimens showed electron-dense gold deposits. Before laser irradiation, these deposits were 106 +/- 35 (mean +/- SD) nm in diameter and faceted, consistent with a crystalline structure. Posttreatment deposits were round, smaller, measured 16 +/- 4 nm, and resembled colloidal gold. Identical findings were observed in an area of sun-protected skin treated with the Q-switched ruby laser; irradiation with a pulsed dye laser at 585 nm had no effect.
Conclusions: Localized chrysiasis was induced in a patient receiving parenteral gold therapy who underwent treatment with a Q-switched ruby laser. This form of chrysiasis resulted from a structural alteration in dermal gold deposits. A similar physiochemical modification in gold deposits induced by UV light may explain the localization of chrysiasis to sun-exposed skin in affected patients.