Heavy metal levels and delta-amino-levulinic acid dehydrase levels in peripheral polyneuropathy

On the basis of assay of heavy metals in whole blood (lead, cadimum, chromium, copper, nickel and manganese) and delta-amino-levulinic-acid dehydrase (ALA-D) and ALA in urine in a normal Danish population, the levels of these clinco-chemical factors were assayed in 23 patients with peripheral neuropathy of unknown etiology. All patients studied showed electro-physiological sign of denervation and/or reduced motor or sensoric nerve conduction velocity. Cadmium and manganese were never found to be increased. In all but four patients, an increase of one or more heavy metals was found. Ten patients showed raised levels of two or more metals, the dominant metal being lead (10 cases), nine patients showed increased in chromium. A significant corrleation was found between increasing lead levels and decreasing ALA-D activity. Although normal concentrations of manganese were found, correlation analysis revealed a significant correlation between increased manganese and decreased ALA-D. The raised values of heavy metals could not be traced to occupational or other exposure to heavy metals and the increased values were not related to tobacco consumption. The findings are discussed in relation to known data on neuropathy and the results seem to indicate a multifactorial patholgenesis of the disease. Among factors contributing to the precipitation of the syndrome may be raised levels of heavy metals.