Thallium poisoning

Thallium poisoning is a toxicologic disorder that can produce neuropsychiatric and multisystemic manifestations, with clinical features varying according to the dose, route, and duration of exposure. A distinctive presentation may include the combination of behavioural or personality change, painful peripheral neuropathy, gastrointestinal symptoms, characteristic hair loss, and a relevant environmental, occupational, or intentional exposure.

Exposure clues include occupational exposure in industries involving thallium compounds, particularly metal processing, electronics, and other industrial settings. Exposure may also occur through contaminated food or water, traditional or medicinal products, or deliberate ingestion of thallium-containing substances. Both ingestion and inhalation are recognized routes of exposure, although ingestion is the most common route in acute poisoning.

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

Other characteristic features include a painful, predominantly sensory peripheral neuropathy with burning pain, paresthesias, numbness, and progressive weakness, which may become severe or involve both sensory and motor fibres. Other neurological manifestations may include ataxia, tremor, cranial neuropathies, encephalopathy, and, in severe poisoning, seizures or coma. Cardiovascular manifestations may include tachycardia, hypertension or hypotension, and cardiac arrhythmias, with severe poisoning potentially causing cardiovascular instability. Renal manifestations may include proteinuria, hematuria, renal tubular injury, and, in severe poisoning, acute kidney injury. Hematologic abnormalities, including anemia and leukocytosis, may also occur.

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

• Gastrointestinal: Abdominal pain, nausea, vomiting and diarrhea, which may occur early after acute ingestion.

• Dermatologic: Alopecia, typically diffuse and involving the scalp and body hair, is a characteristic delayed manifestation; Mees' lines and other nail abnormalities may also occur.

Early diagnosis is important because thallium poisoning can cause severe and potentially irreversible neurological injury, autonomic dysfunction, and multiorgan complications. Prompt recognition allows removal from the exposure source, appropriate toxicologic assessment, and consideration of specific antidotal treatment and enhanced elimination strategies when indicated.