The usual manifestations of lead poisoning in adults are colic, anemia, and peripheral neuropathy. Encephalopathy of the type described above is decidedly rare. Lead colic, frequently precipitated by an intercurrent infection or by alcohol intoxication, is characterized by severe, poorly localized abdominal pain, often with rigidity of abdominal muscles but without fever or leukocytosis. The pain responds to the intravenous injection of calcium salts, at least temporarily, but responds poorly to morphine. Mild anemia is common. A black line of lead sulfide may develop along the gingival margins. Peripheral neuropathy, usually a bilateral wrist drop, is a rare manifestation and is discussed in Chap. 46.
The diagnostic tests for plumbism in children are generally applicable to adults, with the exception of bone films, which are of no value in the latter. Also, the treatment of adults with chelating agents follows the same principles as in children.
Intoxication with tetraethyl and tetramethyl (organic) lead, used as additives in gasoline, is caused by inhalation of gasoline fumes. It occurs most often in workers who clean gasoline storage tanks. Insomnia, irritability, delusions, and hallucinations are the usual clinical manifestations, and a maniacal state may develop. The hematologic abnormalities of inorganic lead poisoning are not found, and chelating agents are of no value in treatment. Organic lead poisoning is usually reversible, but fatalities have been reported. The pathologic changes have not been well described.
In the past, medications such as Fowler solution (potassium arsenite) and the arsphenamines, used in the treatment of syphilis, were frequent causes of intoxication, but now the most common cause is the suicidal or accidental ingestion of herbicides, insecticides, or rodenticides containing copper acetoarsenite (Paris green) or calcium or lead arsenate. In rural areas, arsenic-containing insecticide sprays are a common source of poisoning. Arsenic is used also in the manufacture of paints, enamels, and metals; as a disinfectant for skins and furs; and also in galvanizing, soldering, etching, and lead plating. Occasional cases of poisoning are reported in relation to these occupations. Arsenic is still contained in some topical creams and oral solutions that are used in the treatment of psoriasis and other skin disorders and in some herbal remedies.
Arsenic exerts its toxic effects by reacting with the sulfhydryl radicals of certain enzymes necessary for cellular metabolism. The effects on the nervous system are those of an encephalopathy or peripheral neuropathy. The latter may be the product of chronic poisoning or may become manifest between 1 and 2 weeks after recovery from the effects of acute poisoning. It takes the form of a distal axonopathy that is described in Chap. 43 (see also Heyman et al). In cases of arsenical polyneuropathy we have cared for, a distal sensorimotor areflexic syndrome developed subacutely. At autopsy there was a dying back pattern of myelin and axons with macrophage and Schwann cell reactions and chromatolysis of motor neurons and sensory ganglion cells. The CNS appeared normal.