An unsolved mystery: idiopathic thallium exposure resulting in clinically significant toxic effects
Vohra V, Baltarowich L, Syed S, and Aaron C. An unsolved mystery: idiopathic thallium exposure resulting in clinically significant toxic effects. Clin Toxicol 2021; 59(6):596-597.
Objective: Thallium rodenticide was banned in the US in 1972 but poisoning cases persist due to suicide, homicide, herbal product contamination, depilatories, and illicit drug adulteration. We present a report of a thallium exposure resulting in significant toxicity.
Case report: A 41-year-old male with a history of juvenile myoclonic epilepsy on divalproex sodium, amlodipine, gabapentin and hydrocodone/acetaminophen presented with generalized weakness, difficulty ambulating, vague gastrointestinal symptoms, and progressive distal paresthesias. Diagnosed with atypical Guillain-Barré syndrome he received IV immunoglobulin (IVIG) and corticosteroids and was discharged to a rehabilitation facility. He was re-admitted with visual and auditory hallucinations, disorientation, memory deficiencies, encephalopathy, seizures, and worsening neuropathy with four limb weakness. He was given IVIG and corticosteroids. Magnetic resonance imaging (MRI) of brain and spine were unremarkable. Electromyography-nerve conduction velocity studies showed progression of subacute distal motor neuropathy greater than sensory axonal peripheral neuropathy. He also developed alopecia and a serum thallium concentration was sent (Table 1). Family, social, and occupational history were unremarkable. Vital signs were blood pressure 141/ 93mmHg; heart rate 96 bpm; respiratory rate 16 breaths/min; oxygen saturation 97% (room air); temperature 36.4 °C. Physical examination was remarkable for encephalopathy and bradykinesis with visual hallucinations, short-term memory deficit, tremors and profound weakness with areflexia, and painful hyperesthesias. A comprehensive metabolic panel and initial heavy metal screen were unremarkable with normal thyroid testing. He received multi-dose activated charcoal, and Prussian blue (3 g 8 hourly via a nasogastric tube) over 3 weeks until concentration of thallium were /mL. He was hospitalized for 3.5 months then transferred for rehabilitation for residual motor weakness. He had total body alopecia. The source of thallium remains undetermined.
Conclusion: This is a case involving thallium exposure of unknown etiology resulting in elevated serum concentrations with pronounced clinical toxicity. It remains an open investigation.