Urinary excretion of lead and mercury after oral administration of meso-2,3-dimercaptosuccinic acid in patients with motor neurone disease.

Amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA) are progressive neurodegenerative disorders involving motor neurones. The aetiology of the non-familiar forms is still unknown but it has been suggested that long-term exposure to heavy metals such as lead and mercury may play a role in the pathogenesis of these diseases. In 53 patients suffering from ALS (n = 42) and SMA (n = 9) the oral administration of dimercaptosuccinic acid (DMSA, 20 mg/kg) did not result in a greater mobilization of lead and mercury from peripheral depots than in control subjects. Although it cannot be excluded that the amount of lead or mercury excreted after DMSA administration may not be a reflection of the amount accumulated in the motor neurons, this study does not provide support for the hypothesis that heavy metals play a significant role in the occurrence of motor neurone diseases.