Conjugal amyotrophic lateral sclerosis: toxic clustering or change?

We describe a southern Italian couple, married for 28 years, who developed amyotrophic lateral sclerosis (ALS) within 30 months of each other. They had drunk water taken from an artesian well for nearly thirty years. Samples of the water were investigated in the search for heavy metals and pesticides using high performances liquid chromatography, gas chromatography and absorption spectrometry. No heavy metals, pesticides or known environmental toxic substances were found in significant concentration. This would seem to support the view that conjugal ALS in Caucasians is due to mere coincidence.