# Personalized Prevention in Mercury-Induced Amyotrophic Lateral Sclerosis: A Case Report
## 2 Case Presentation  
A 54-year-old male worker has been working in a large chlor-alkali plant in Central Italy since 1986 as a small industrial plant maintenance contractor. He mainly performed maintenance activities in Hg cells, where Hg cathodes were working in brine (saltwater--mainly sodium chlorine or, to a lesser extent, potassium chloride), or was assigned to piping and filter cleaning. He was exposed to inorganic Hg, as well as other chemical (chloromethane, acids and bases, welding fumes) and physical (noise, heavy load handling) agents. The medical history was not contributory, but the familiar history was noticeable for neurological disorders in first degree relatives (i.e., his mother was affected by [PERSON]'s disease and deceased from a stroke, two brothers were affected by myogenic torticollis). He had middle-lower education and was not a smoker. The patient followed the Mediterranean diet, consuming fish on average 3-5 times per month. He was subjected to periodic medical examinations supplemented by biological monitoring of urinary Hg tests (U-Hg) through occupational health surveillance programs. In 1988, after working on cleaning mercury cells, he manifested tremor, vertigo, marked weakness, ataxia, and fever. U-Hg level of 127 ug/g creatinine, significantly higher than the biological exposure limit BEI(r) (20 ug/g creatinine), was observed. He was temporarily removed from the job for two weeks, but no occupational injury was reported to the competent authorities. In the following years, a certain number of episodes of malaise, dizziness or confusion, agitation, and insomnia, associated with U-Hg values between 60 and 80 ug/g creatinine, occurred. None of these recurrent episodes of subacute intoxication were reported to the competent Italian authorities. The occupational physician responsible for medical surveillance of workers declared him \"fit for work\". As a result, he was employed with the same working tasks for over 20 years. In 2008, the same occupational physician prescribed that he could not be exposed to respiratory irritants and chemical risk. Despite this restriction, however, he continued his previous activities. In October 2012, at the end of the work shift, he reported unpleasant metallic taste, nausea, dry mouth, difficulty in swallowing, and voice lowering. In the following working days, other symptoms appeared, such as marked weakness, muscle cramps, intentional tremors hindering work performance (e.g., welding of metal staples). In August 2013, fasciculations of the upper limbs and trunk were also evident. Electromyographic examination showed denervation potentials in the upper limb muscles (deltoid muscle bilaterally and the right vastus lateralis) and abnormal spontaneous activity in the lower limb muscles (plantar interosseous and anterior tibial muscle, bilaterally). In December 2013, he came to our attention. Neurological examination showed high-frequency postural tremor (right side \(>\) left side) occurring in standing position, with dysarthria and tongue fasciculations, weakness and atrophy of the small hand muscles, fasciculation in all four limbs, with no signs of pyramidal tract involvement. Hematochemical parameters were normal. Brain MRI scan documented no signs of brain impairment. In March 2014, lung function tests showed a restrictive deficit, supposed to be a consequence of limited diaphragm excursion due to neurological impairment. Genetic screening for [PERSON] disease showed a negative result in the target gene (Androgen Receptor, AR). In consideration of the history of recurrent episodes of Hg intoxication, we reported the suspicion of occupational mercury poisoning to the National Italian Occupational Insurance Authority (INAIL), which refused the claim. The patient continued to be treated by the Neurology Department of our university hospital, which diagnosed amyotrophic lateral sclerosis. Over the following years, he presented progressive weakness involving proximal upper limbs and respiratory muscles.