CASE REPORT article
Front. Toxicol.
Sec. Occupational Toxicology
Volume 7 - 2025 | doi: 10.3389/ftox.2025.1580275
Mercury exposure leading to functional vitamin B12 deficiency and subacute combined degeneration, a case report and literature review
Provisionally accepted- 1Department of Neurology, Faculty of Medicine, University of Rijeka, Rijeka, Rijeka, Croatia
- 2Department of Neurology, Clinical Hospital Center Rijeka, Rijeka, Croatia
Select one of your emails
You have multiple emails registered with Frontiers:
Notify me on publication
Please enter your email address:
If you already have an account, please login
You don't have a Frontiers account ? You can register here
Introduction: The association between neurological symptomatology and heavy metal exposure has been reported in the literature. A few cases of extrapyramidal symptomatology and subacute combined degeneration were described as a manifestation of mercury intoxication. We highlight a case of a patient with Parkinsonian features (tremor, rigidity, bradykinesia), pyramidal deficits, dysarthria, paresthesia, mild cognitive decline, and emotional lability with proven elevated mercury levels in the blood and hair and elevated arsenic in urine. Case: A 60-year-old man, with history of exposure to mercury while working in the Centre for Waste Management and Environmental Protection presented to the neurologist after 10- months of persistant tremors, muscle spasms, paresthesia, and irritability, followed by the appearance of bradykinesia, slurred speech, rigidity, insomnia, and subtle cognitive decline. Laboratory investigations disclosed functional vitamin B12 and vitamin D deficiencies, while toxicological quantitative analysis showed elevated blood mercury levels (15.2 μg/L) and hair roots (3μg/g). MRI of the brain was normal, and an MRI of the posterior cervical spine detected signs of myelopathy. FDG PET of the brain registered bilateral temporal and parietal glucose hypometabolism, most pronounced inleft inferior parietal and left superior temporal regions. SPECT imaging of dopaminergic neurons in the striatum was negative, and the patient was levodopa-unresponsive. Multivitamin therapy (Vitamin B, E, and D) with selenium added to symptomatic therapy (benzodiazepines, muscle relaxants, antidepressive) provided minimal relief, leading to the introduction of N-acetyl cysteine, resulting in a moderate improvement of symptoms. Physical and speech therapy were of great importance in this case. Discussion: This case is unique because it represents the development of therapy-resistant extrapyramidal symptoms developed during 3 years of mercury exposure, likely leading to a subacute combined degeneration due to functional vitamin B12 deficiency. Epidemiological data provide information about methylmercury poisoning known as Minamata disease- somatosensory deficits, ataxia, parkinsonism, dysarthria, visual and hearing problems Conclusion: Toxicological screening for heavy metals in blood and urine should be considered in patients presenting with unexplained, levodopa-resistant extrapyramidal symptoms, behavioral and sleep disturbances, cognitive decline, and other non-specific neurological signs.
Keywords: Mercury, intoxication, B12-deficiency, combined degeneration of spinal cord, extrapyramidal symptoms
Received: 20 Feb 2025; Accepted: 04 Aug 2025.
Copyright: © 2025 Semnic, Racki and Vuletić. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Valentino Racki, Department of Neurology, Clinical Hospital Center Rijeka, Rijeka, Croatia
Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.