A skin-lightening cream from Mexico has been found to have had a devastating effect on the central nervous system due to its highly toxic mercury levels, according to a UC San Francisco-led report on a patient who remains unable to care for herself months after ceasing use of the product.
The cream was found to contain methylmercury, a form of organic mercury, and is the first case of such poisoning in the United States in nearly 50 years, the authors state in their report, which publishes Dec. 19, 2019, in the Morbidity and Mortality Weekly Report, by the U.S. Centers for Disease Control and Prevention (CDC).
In this case, the patient used a skin-lightening product containing organic mercury, which is far more toxic. This form of mercury can cause profound damage to the central nervous system that may even worsen after cessation of use.
“Most harmful skin-lightening creams are intentionally tainted with inorganic mercury,” said senior author Paul Blanc, MD, MSPH, of the UCSF Division of Occupational and Environmental Medicine, and the California Poison Control System, San Francisco Division. “But in this case, the patient used a skin-lightening product containing organic mercury, which is far more toxic. This form of mercury can cause profound damage to the central nervous system that may even worsen after cessation of use.”
The authors recount that the patient initially sought medical help for involuntary muscle movements and weakness of her upper extremities. After two weeks of outpatient care, the patient’s condition had deteriorated. She was admitted to a local hospital with symptoms that had progressed to blurry vision, unsteady gait and difficulty with speech.
Blood and Urine Tests Confirm Diagnosis
Mercury poisoning was confirmed after elevated blood and urine levels of the metal were found, but it was not initially known if inorganic or organic mercury was implicated. The patient’s family disclosed that she had been applying skin-lightening creams, obtained from Mexico, twice a day for seven years.
The patient underwent chelation therapy, a treatment for heavy metal poisoning in which a chelator drug binds to the metal in the blood stream and is excreted in the urine. While the therapy corresponded with a drop in blood mercury, the patient’s condition did not improve.
The patient was transferred to UCSF, where clinicians raised suspicions of organic mercury poisoning. Further testing by the California Department of Public Health indicated that the skin-whitening cream had been contaminated with methylmercury iodide; methylmercury was confirmed by the CDC.
Many weeks after the initial hospitalization, the patient requires “ongoing tube feeding for nutritional support” and is unable to speak or care for herself, the authors report. Additionally, the California Department of Public Health is investigating likely exposure to the same product in a family member.
“Central nervous system toxicity, as in this case, is the hallmark of organic mercury – it typically comes on after weeks to months of exposure. Once manifested, it quickly progresses and often worsens, despite removal of any further exposure,” Blanc said. “Unfortunately, chelation therapy, which is effective in inorganic mercury poisoning, has not been established to be efficacious for methylmercury.”
Consumers purchasing skin creams should check that the product has a protective foil seal under the lid, said co-author Craig Smollin, MD, of the UCSF Department of Emergency Medicine and medical director of the California Poison Control System, San Francisco Division. “They should purchase creams from well-known stores and avoid those with hand-made labels or without labels. Ingredients must be listed, and directions and warnings should be in English.”
Authors: First author is Anita Mudan, MD, of the UCSF Department of Emergency Medicine and the California Poison Control System, San Francisco Division. There are 14 other co-authors from the California Poison Control System; UCSF; California Department of Public Health; Centers for Disease Control and Prevention; Dignity Health Care System, Sacramento; and UC Davis.
The University of California, San Francisco (UCSF) is exclusively focused on the health sciences and is dedicated to promoting health worldwide through advanced biomedical research, graduate-level education in the life sciences and health professions, and excellence in patient care. UCSF Health, which serves as UCSF’s primary academic medical center, includes top-ranked specialty hospitals and other clinical programs, and has affiliations throughout the Bay Area.