Q-Switched Laser-Induced Chrysiasis Treated With Long-Pulsed Laser

A 70-year-old woman presented for elective treatment of lentigines on her face. This was her first treatment with any laser. She was treated with a Q-switched alexandrite laser (755 nm, 50 nanoseconds, 3.5 J/cm, 15 pulses of 4-mm spot diameter; Candela, Wayland, Mass), causing what appeared to be usual purpura immediately following laser exposure of 8 tan macules. Several weeks later, blue-black discoloration was present, and was attributed to postinflammatory hyperpigmentation, but failed to lighten over the next 4 months. Her medical history was significant for rheumatoid arthritis, treated with methotrexate and prednisone. Further questioning revealed that she had received a 3-year course of oral gold therapy 20 years prior. The total dosage taken could not be determined. Four months following Q-switched alexandrite laser therapy, her examination revealed 8 blue macules without texture changes located at the laser treatment sites on her cheeks and forehead ranging from 2 to 6 mm (Figure 1). The lesions did not enhance on Wood’s light examination, suggesting dermal pigmentation. In some areas, portions of the original lentigo were still visible in the center of the blue macule. There was no discoloration of the sclera, nails, or hair. A subtle blue-gray hue in the patient’s general skin color was noted at the time of reexamination. Apunchbiopsyspecimenofarepresentativeareademonstrated numerous black particles within macrophages in the dermis. A diagnosis of Q-switched laser-induced chrysiasis was made. Initially, an attempt was made to clear the hyperpigmentation using the same Q-switched laser, a technique that can often lighten or clear laser-induced cosmetic tattoo darkening. A test spot was created on the inner aspect of the right arm with the original Qswitched alexandrite laser, and the hyperpigmented macule was pulsed again with the same laser. While the center of the lesion did show some clearing, a new rim of blue hyperpigmentation was induced around the treated spot. Further treatment with a Q-switched alexandrite laser was therefore not pursued, because blue pigmentation would always be induced at the border of the treated area. Surgical excision was considered but not pursued, given the number and location of the lesions.