A middle-aged female research scientist was admitted to the hospital with a history of progressive loss of balance and speech over five days. She experienced weight loss of 15 pounds, nausea, diarrhea, and abdominal pain over the previous two months. Her initial presentation was characterized by anxiety related to her recent symptoms. Physical examination revealed upper extremity dysmetria and dystaxic handwriting. MRI and CT scans of the head were normal, indicating no acute intracranial pathology. Routine laboratory tests were within normal limits.
The patient recalled a laboratory accident five months prior where she spilled a chemical onto her latex gloves. She cleaned up the spill, recorded the incident in her laboratory notebook, and gave it no further thought. Given the severity and progression of her symptoms, the spill became the focal point of the investigation.
What is the possible identity of the toxin causing this woman's findings?
a) Iron chloride
b) Sodium arsenite
c) Mercury
d) Chlorpromazine, an antipsychotic drug
Reveal the answer
To determine the toxin responsible for the patient's symptoms, we need to consider the potential toxic effects and the likelihood of these substances causing primarily central nervous system (CNS) symptoms.
Iron Chloride and Sodium Arsenite: These compounds are known for their toxicity; however, they typically do not manifest primarily as CNS symptoms when exposure is dermal. Furthermore, large doses are required to penetrate the skin and cause systemic effects, which makes them less likely to be the cause in this scenario.
Iron Chloride: Iron chloride is known for its toxic effects when ingested or when there is significant exposure. However, its toxicity does not typically manifest primarily as CNS symptoms when exposure is dermal. Here are some key points from the literature:
• Acute Poisoning: Iron poisoning is typically characterized by gastrointestinal symptoms, metabolic acidosis, and multi-organ failure in severe cases. There is a noted absence of CNS symptoms as primary effects in cases of acute iron poisoning (Skoczyńska et al., 2007; Chen et al., 1993).
• Dermal Exposure: A study comparing the systemic toxicity of various compounds, including mercuric chloride, through dermal exposure showed significant effects on body weight, proteinuria, and renal function but did not highlight CNS effects as a primary concern (Staab & Tierney, 1984).
• Caustic Injury: Ferric chloride ingestion can lead to severe caustic injury in the gastrointestinal tract, highlighting its primary toxicity route via ingestion rather than dermal exposure (Menendez et al., 2015).
Sodium Arsenite: Sodium arsenite is a known toxicant with significant health impacts, particularly when ingested. However, its primary route of causing severe CNS effects through dermal exposure is less documented.
• General Toxicity: Arsenic compounds, including sodium arsenite, are known for their systemic toxicity affecting multiple organs, but they typically require significant exposure to cause severe systemic effects (Repko & Lasley, 1979).
• Dermal Absorption: The rate of dermal absorption and subsequent systemic effects of sodium arsenite is less well-documented compared to ingestion. The primary effects are usually gastrointestinal and renal rather than CNS when systemic toxicity occurs (Sayadi et al., 2020).
Chlorpromazine: Chlorpromazine, an antipsychotic drug, is usually administered in its aqueous form. This form should not penetrate latex gloves significantly. Additionally, a very large quantity would be needed to provoke such symptoms, making it an improbable cause.
Mercury: Mercury, especially in its organic forms like dimethylmercury, is highly toxic and can be absorbed through latex gloves. Once absorbed, it can cause severe and primarily CNS symptoms. Studies have shown that latex gloves do not provide adequate protection against organic mercury compounds. This makes mercury a strong candidate as the causative agent in this case.
Laboratory testing confirmed extremely high levels of mercury in the patient's blood and urine. Despite chelation therapy, the patient's condition continued to deteriorate, leading to a comatose state and eventual death. Autopsy findings revealed significant brain abnormalities and mercury content approximately six times higher than blood levels.
The toxin causing the woman's findings is c) Mercury.
While both iron chloride and sodium arsenite are toxic substances, their toxicity primarily manifests through ingestion rather than dermal exposure. Furthermore, the systemic absorption necessary to cause significant CNS symptoms typically requires larger doses than what would be expected through minor dermal contact, making them less likely causes for the described CNS symptoms in the case study.
This case highlights the critical need for proper safety protocols and protective equipment when handling toxic substances in laboratory settings. Awareness and prompt action in the event of accidental exposure can significantly mitigate the risks associated with these dangerous compounds.
© All copyright of this material is absolute to Medical toxicology
Authors:
Bio:
Dr. Omid Mehrpour is a distinguished medical toxicologist known for his extensive clinical and research expertise. He focuses on understanding and treating toxic exposures. Renowned for his ability to diagnose and manage poisoning cases, Dr. Mehrpour has authored numerous impactful publications and is dedicated to educating future medical toxicologists. His innovative approach and commitment to patient care make him a leading figure in medical toxicology.
References:
1) Fenton, John Joseph. Toxicology: A Case-Oriented Approach. CRC Press, 2001. https://doi.org/10.1201/9781420042061
2) Skoczyńska, A., Kwiecińska, D., & Kiełbiński, M. (2007). Acute iron poisoning in adult female. Human & Experimental Toxicology, 26, 663-666.
3) Staab, R., & Tierney, W. (1984). Repeat Dermal Models for Systemic Toxicity: A Comparison of the Rabbit, Rat and Guinea Pig.
4) Repko, Jd., & Lasley, Sm. (1979). Behavioral, neurological, and toxic effects of methyl chloride: a review of the literature. Critical Reviews in Toxicology, 6, 283-302.
5) Sayadi, M., Mansouri, B., Shahri, E., Tyler, C., Shekari, H., & Kharkan, J. (2020). Exposure effects of iron oxide nanoparticles and iron salts in blackfish (Capoeta fusca): Acute toxicity, bioaccumulation, depuration, and tissue histopathology. Chemosphere, 247, 125900.
6) Chen, M. R., Lin, J. L., Liaw, S. J., & Bullard, M. J. (1993). Acute iron intoxication: a case report with ferric chloride ingestion. Zhonghua yi xue za zhi = Chinese medical journal; Free China ed, 52(4), 269-272.
7) Menendez, A., Abramson, L., Vera, R., Duza, G. E., & Palermo, M. (2015). Total gastrectomy due to ferric chloride intoxication. Acta gastroenterologica Latinoamericana, 45(3), 212-216.