Inorganic mercury compounds are formed when elemental mercury combines with sulfur or oxygen and often take the form of mercury salts, which appear as white crystals.16 These salts occur naturally in the environment and are used in pesticides, antiseptics, and skin-lightening creams and soaps.18
Methylmercury is a highly toxic, organic compound that is capable of crossing the placental and blood-brain barriers. It is the most common organic mercury compound found in the environment.16 Most humans have trace amounts of methylmercury in their bodies, typically as a result of consuming seafood.5
Exposure to mercury most commonly occurs through chronic consumption of methylmercury in seafood or acute inhalation of elemental mercury vapors.9 Iatrogenic cases of mercury exposure via injection also have been reported in the literature, including a case resulting in acute poisoning due to peritoneal lavage with mercury bichloride.19 Acute mercury-induced pulmonary damage typically resolves completely. However, there have been reported cases of exposure progressing to interstitial emphysema, pneumatocele, pneumothorax, pneumomediastinum, interstitial fibrosis, and chronic respiratory insufficiency, with examples of fatal acute respiratory distress syndrome being reported.5,16,20 Although individuals who inhale mercury vapors initially may be unaware of exposure due to little upper airway irritation, symptoms following an initial acute exposure may include ptyalism, a metallic taste, dysphagia, enteritis, diarrhea, nausea, renal damage, and CNS effects.16 Additionally, exposure may lead to confusion with signs and symptoms of metal fume fever, including shortness of breath, pleuritic chest pain, stomatitis, lethargy, and vomiting.20
Chronic exposure to mercury vapor can result in accumulation of mercury in the body, leading to neuropsychiatric, dermatologic, oropharyngeal, and renal manifestations. Sore throat, fever, headache, fatigue, dyspnea, chest pain, and pneumonitis are common.16 Typically, low-level exposure to elemental mercury does not lead to long-lasting health effects. However, individuals exposed to high-level elemental mercury vapors may require hospitalization. Treatment of acute mercury poisoning consists of removing the source of exposure, followed by cardiopulmonary support.16
Specific assays for mercury levels in blood and urine are useful to assess the level of exposure and risk to the patient. Blood mercury concentrations of 20 µg/L or below are considered within reference range; however, once blood and urine concentrations of mercury exceed 100 µg/L, clinical signs of acute mercury poisoning typically manifest.21 Chest radiographs can reveal pulmonary damage, while complete blood cell count, metabolic panel, and urinalysis can assess damage to other organs. Neuropsychiatric testing and nerve conduction studies may provide objective evidence of CNS toxicity. Assays for N-acetyl-β-D-glucosaminidase can provide an indication of early renal tubular dysfunction.16
Elemental mercury is not absorbed from the gastrointestinal tract, posing minimal risk for acute toxicity from ingestion. Generally, less than 10% of ingested inorganic mercury is absorbed from the gut, while elemental mercury is nonabsorbable.10 If an individual ingests a large amount of mercury, it may persist in the gastrointestinal tract for an extended period. Mercury is radiopaque, and abdominal radiographs should be obtained in all cases of ingestion.16
Mercury is toxic to the CNS and peripheral nervous system, resulting in erethism mercurialis, a constellation of neuropsychologic signs and symptoms including restlessness, irritability, insomnia, emotional lability, difficulty concentrating, and impaired memory. In severe cases, delirium and psychosis may develop. Other CNS effects include tremors, paresthesia, dysarthria, neuromuscular changes, headaches, polyneuropathy, and cerebellar ataxia, as well as ophthalmologic and audiologic impairment.5,16
Upon inhalation exposure, patients with respiratory concerns should be given oxygen. Bronchospasms are treated with bronchodilators; however, if multiple chemical exposures are suspected, bronchial-sensitizing agents may pose additional risks. Corticosteroids and antibiotics have been recommended for treatment of chemical pneumonitis, but their efficacy has not been substantiated.16
Skin reactions associated with skin contact to elemental mercury are rare. However, hives and dermatitis have been observed following accidental contact with inorganic mercury compounds.5 Manifestation in children chronically exposed to mercury includes a nonallergic hypersensitivity (acrodynia),5,17 which is characterized by pain and dusky pink discoloration in the hands and feet, most often seen in children chronically exposed to mercury absorbed from vapor inhalation or cutaneous exposure.16
Renal conditions associated with acute inhalation of elemental mercury vapor include proteinuria, nephrotic syndrome, temporary tubular dysfunction, acute tubular necrosis, and oliguric renal failure.16 Chronic exposure to inorganic mercury compounds also has been reported to cause renal damage.5 Chelation therapy should be performed for any symptomatic patient with a clear history of acute elemental mercury exposure.16 The most frequently used chelation agent in cases of acute inorganic mercury exposures is dimercaprol. In rare cases of mercury intoxication, hemodialysis is required in the treatment of renal failure and to expedite removal of dimercaprol-mercury complexes.16
Cardiovascular symptoms associated with acute inhalation of high levels of elemental mercury include tachycardia and hypertension.16 Increases in blood pressure, palpitations, and heart rate also have been observed in instances of acute elemental mercury exposure. Studies show that exposure to mercury increases both the risk for acute myocardial infarction as well as death from coronary heart and cardiovascular diseases.5
Conclusion
Mercury poisoning presents with varied neuropsychologic signs and symptoms. Our case provides insight into a unique route of exposure for mercury toxicity. In addition to the unusual presentation of a mercury granuloma, our case illustrates how surgical techniques can aid in removal of cutaneous reservoirs in the setting of percutaneous exposure.