Mercury poisoning

Mercury poisoning is a toxicologic disorder that can produce neuropsychiatric and multisystemic manifestations, with clinical features varying according to the form, dose, route, and duration of exposure. A distinctive presentation may include the combination of behavioural or personality change, tremor, peripheral neuropathy, gingivostomatitis, and a relevant exposure history.

Exposure clues that may be particularly relevant to psychiatric manifestations include occupational or environmental exposure to elemental mercury vapor, particularly through artisanal or small-scale gold mining, amalgam burning, mercury-related industrial work, or recycling. Other forms of mercury exposure include ingestion of mercury-contaminated fish or seafood, as well as exposure through certain traditional medicines, cosmetics, or other mercury-containing products; these can also produce neurotoxicity but have different characteristic clinical patterns.

It can present with psychiatric features such as irritability, emotional lability, anxiety, depression, insomnia, impaired concentration, and personality or behavioural change. Psychotic symptoms, including hallucinations and delusional or paranoid phenomena, have also been reported, although the available literature does not consistently establish to what extent these may occur outside the context of delirium.

Other characteristic features include fine tremor, which may progress to more pronounced or coarse tremor, peripheral paresthesias or neuropathy, weakness, ataxia, impaired coordination, and visual or hearing disturbances, particularly with methylmercury exposure. Cognitive impairment and memory disturbance may also occur. Gingivitis, stomatitis, excessive salivation, and a metallic taste are characteristic clues, particularly with elemental or inorganic mercury exposure.

From a multisystemic lens perspective, clinical features in other body systems include (but are not limited to):

• Renal/electrolytes: Proteinuria, tubular injury, nephrotic syndrome and, with severe acute inorganic mercury poisoning, acute kidney injury or renal failure.

• Respiratory: Cough, dyspnea, chest discomfort and pneumonitis following substantial inhalational exposure to elemental mercury vapor; severe acute exposure may cause pulmonary edema or respiratory failure.

• Gastrointestinal: Nausea, vomiting, abdominal pain, diarrhea and, particularly with acute ingestion of inorganic mercury salts, severe gastroenteritis that may be hemorrhagic.

Early diagnosis is important because mercury poisoning can cause persistent or irreversible neurological injury and, depending on the form and severity of exposure, significant renal, gastrointestinal, respiratory, or other systemic complications. Prompt recognition allows removal from the exposure source, appropriate toxicologic assessment, and consideration of chelation therapy when indicated.