Lead Intoxication Caused by Skeletal Disease

Background Inorganic lead is accumulated in the skeleton, which harbors more than 90% of the body burden of lead. If rapidly mobilized, this pool may constitute a health risk. However, clear evidence of this theory has been lacking. History A previously healthy 36-year-old Swedish man with more than 10 years of work-related lead exposure developed headache, musculoskeletal pain, and paresthesia of both arms. Two months after the cessation of exposure, the lead level in his blood (B-Pb) was 5.5 μmol · l⁻¹, and treatment with chelating agents was started. Shortly after the treatment period, he had an accident causing a fracture of the right collum femoris. The B-Pb was fairly stable around 1.5 μmol · l⁻¹ for about two years after the end of exposure (95th percentile 0.6 μmol · l⁻¹ for occupationally unexposed Swedish men). The examination showed that the patient had high skeletal turnover and clearly reduced bone density, as well as signs of tubular dysfunction. He was given the diagnosis idiopathic osteoporosis. His moderately raised bone lead concentration (about 20 μg · g wet weight⁻¹; normal level in Sweden 4 μg · g⁻¹) can only partly explain the raised B-Pb, remaining for years after the cessation of exposure. Instead, the main explanation is probably the increased skeletal turnover. Conclusions A combination of a moderately increased bone lead pool and skeletal disease seems to increase the risk for lead poisoning.