The authors’ observations
Mr. F’s mental status changes and serum mercury suggest mercury poisoning. He shows numerous heavy-metal poisoning symptoms (Box 1) as well as erethism, a malaise that can result from heavy-metal exposure.2
The patient insists that insulin shots bring on self-injection urges, but his impulsive and repetitive suicidal behavior, dysphoria, and transient paranoia suggest borderline personality disorder. His impulses may reflect a subtle, long-term personality change caused by mercury’s neurotoxic effects.1 Or they could be akin to cutting behaviors shown by some patients with personality disorders, particularly borderline personality disorder.
We ruled out substance abuse disorder, as Mr. F’s mercury ingestion was not premeditated, he has no history of illicit drug use, and intravenous elemental mercury is not psychoactive.
- Emotional lability
- Excessive shyness
- Headaches
- Hearing loss
- Insomnia
- Irritability
- Lack of ambition
- Lack of sexual desire
- Loss of confidence
- Memory loss
- Nervousness
- Neuromuscular changes (including weakness, muscle atrophy, muscle twitching)
- Performance deficits in cognitive function tests
- Polyneuropathy
- Tremor of hands
- Visual field defects
Source: Reference 1
Elemental mercury found in thermometers, lamps, and dental amalgams slowly ionizes in the blood stream before crossing the blood-brain barrier. Mercury and carbon form toxic “organic” compounds, including methylmercury (found in the environment), phenylmercury (used in some commercial products), and dimethylmercury (found in solid waste sites).
Because mercury’s half-life is 60 days, it dissipates slowly, can accumulate with chronic exposure, and stays in the blood stream long after high-dose exposure.3
Serum mercury >5 mg/dL can cause subtle, enduring neurotoxic effects, including tremor, dizziness, shortness of breath, blurry vision, decreased visual fields, depression, memory loss, and irritability.3 Serum mercury rarely exceeds 1.5 mg/dL without direct exposure.
Irritability, depressive symptoms, and renal manifestations emerge when urine mercury reaches 200 to 1,000 mg/dL. Renal, respiratory, and GI effects are seen at 1,000 to 2,000 mg/dL.
Means of exposure. Vapor inhalation is the most common means of elemental mercury exposure.3 Elemental mercury used in manufacturing vaporizes at room temperature.
Orally ingested elemental mercury is poorly absorbed from the GI tract, mostly passes unabsorbed, and is toxic only at high doses. Injected elemental mercury is poorly absorbed but can cause mechanical and immunologic effects. The psychiatric literature describes some 200 cases of mercury self-injection4-8 but offers little information on cognitive effects or long-term follow-up.
Consider heavy-metal poisoning in the differential diagnosis of patients with depressive symptoms. Ask about risk factors for environmental mercury exposure, including use of folk medicines, some cosmetics, over-the-counter nasal sprays, ophthalmic solutions, skin-lightening creams, daily fish consumption (particularly tuna or swordfish), living in a house painted with latex paint, or continuous exposure at work (Box 2).
Also ask if the patient or a household member recently ingested mercury or handled a broken thermometer. Liquid mercury on clothing and in bodily fluids may cause secondary contamination, whereas mercury vapor cannot.
Order serum mercury testing if you suspect chronic exposure. Refer patients with serum mercury ≥ 1.5 mg/dL to their primary care physicians and to a poison control center for evaluation and possible chelation. Refer patients with acute mercury exposure symptoms to the ER.
Consuming or using certain products or working in some industries increases mercury exposure risk. Mercury-containing products include:
Over-the-counter herbal remedies imported from China, Hong Kong, Haiti, and Cuba.9
Older, larger marine animals, including tuna, shark, or swordfish from mercury-contaminated waters.10,11
Vaccines and medications. Small amounts of thimerosal (ethylmercury sodium salt) were used as a preservative in some vaccines.12 Some antiseptics, eye drops, eye ointments, nasal sprays, skin-lightening creams, and gamma globulin contain mercury.
Dental amalgams are approximately 50% mercury. Each amalgam releases roughly 10 mg/d of mercury; chewing gum or grinding teeth may increase exposure.13 Some suggest removing the fillings, but this can increase mercury exposure if done incorrectly.1
Household goods, including latex paint made before 1990 and broken thermometers.3,14
Other environmental exposure, such as from burning coal, water treatment facilities, landfills, and mercury-containing fungicides.
Occupations that carry a high risk of mercury exposure include:3
Manufacturing
Batteries, cosmetics, explosives, paint/pigments, fluorescent lamps, ink, mercury vapor lamps, pharmaceuticals, switches, and rectifiers
Skilled trades
Plumbing, chlorine and caustic soda production, electroplating, felt-making, leather tanning, grinding machine operators, paper millers
Medical
Dental and medical laboratory personnel
Service industries
Hazardous-waste site personnel, painters, pesticide/fungicide production/application
Mining/processing
Cinnabar, gold, silver, copper, or zinc; metallurgy
The authors’ observations
Antidepressants generally will not reduce depression, irritability, personality changes, or apathy secondary to mercury poisoning. We have found that a psychostimulant such as methylphenidate, starting at 10 mg bid and titrating to therapeutic effect, can help treat mercury-related apathy.