Case Report: Nephrotic syndrome caused by mercury poisoning due to freckle-removing cream.

Nephrotic syndrome caused by mercury poisoning is rare and can often be misdiagnosed. We report a 33-years-old female patient who experienced fatigue and edema of the lower extremities for 1 month. A renal biopsy confirmed the diagnosis of membranous nephropathy (MN) for the patient. Her urinary mercury level was measured at 56.22 ug/L, with a reference range of 0-10 ug/L. A cream used to remove freckles was identified to contain about 13276 mg/kg mercury, which is the possible mercury source. The patient's symptoms improved after chelation therapy, and their urinary mercury levels gradually decreased. After 12 months of follow-up, the patient remained in a state of complete remission. Using mercury-based cosmetics over an extended period can lead to mercury poisoning and trigger MN. Chelation therapy serves as an effective treatment, yielding positive clinical outcomes.