Auditory neurotoxicity and hepatotoxicity after MSMA (monosodium methanarsenate) high dose oral intake.

INTRODUCTION Organic arsenic compounds have been considered of low toxicity compared to inorganic arsenic compounds such as pentavalent and trivalent salts. A recent literature review shows a remarkable lack of toxicological studies or clinical cases of organic arsenic compound intoxication. Most of the works published in this field are related to toxic effects of organic hepatic metabolites of inorganic arsenic, like MMA (monometilarsonic acid) and DMA (dimetilarsinic acid or cacodylic acid), or natural organic forms found in water and fish such as arsenobetaine and arsenocholine. The latter ones (also known as ‘‘fish arsenic’’) have been shown to be essentially nontoxic (1,2). Synthetic forms of organic arsenicals, contained in many pesticides in use today, like MSMA (monosodium methanarsenate), are poorly studied, considering the rather well established low toxicity of fish arsenic. We report a case of MSMA intoxication leading to severe auditory, hepatic and neurological sequelae.