Cupric keratosis: green seborrheic keratoses secondary to external copper exposure

Exogenous copper is a well-known cause of blue-green dyspigmentation of the hair, nails, and skin. We report the case of a patient with a blue-green discoloration of multiple seborrheic keratoses on his chest and back after swimming in a pool for rehabilitation of a back injury. Metallic analysis using atomic absorption spectrometry was performed on water samples from both the swimming pool and the hot tub the patient was using. Our dermatology clinic tap water was used as a control. Results of this analysis revealed an elevated level of copper in the swimming pool (2.750 ppm) and normal levels in the hot tub (0.502 ppm) and the control sample (0.891 ppm). The copper level in the swimming pool was more than double the recommended maximum set forth by the US Environmental Protection Agency. After the patient discontinued water exercises in the swimming pool, the green discoloration of the seborrheic keratoses disappeared rapidly. We believe this case represents the first report in the literature of the discoloration of epidermal growths secondary to exogenous heavy metal exposure.