Clinical Pearls & Morning Reports
Published August 5, 2020
Lead poisoning is a diagnosis that is often overlooked. Lead affects numerous organ systems; common symptoms and signs include gastrointestinal discomfort, constipation, and altered mental status, although the presentation is variable and depends on the duration of exposure. Read the NEJM Clinical Problem-Solving Article here.
Q: What are the causes of microcytic anemia?
A: The most common cause of microcytic anemia is iron deficiency; the other conditions that can cause microcytic anemia are thalassemia, inflammation, sideroblastic anemia (congenital or acquired), and lead poisoning.
Q: Is there a connection between opium use and lead poisoning?
A: Lead-contaminated opium has led to thousands of cases of lead poisoning in the Middle East and several cases in Europe and Australia. In Iran and other Middle Eastern countries, numerous cases of lead poisoning from lead-contaminated opium have been reported. During an 18-month period from 2016 to 2017, more than 4000 persons across two large hospitals in Tehran were treated for lead poisoning resulting from ingestion of opium. The reason for lead contamination in opium is not known, but two leading hypotheses are that lead is added to increase the weight, thereby increasing profit, or that it results from the manufacturing process.
A: Features commonly seen on physical examination that are consistent with lead poisoning include bluish pigmentation at the gum line (termed “lead lines”); hypertension, seen in patients with long-term exposure; and peripheral neuropathy. Mild long-term elevations of the blood lead level (>10 μg per deciliter [0.5 μmol per liter]) are associated with an increased risk of cardiovascular disease, renal dysfunction, and neurocognitive effects, highlighting the need to avoid even low-level exposure. Anemia typically manifests at a blood lead level of greater than 50 μg per deciliter (2.4 μmol per liter). Severe encephalopathy, which can include the occurrence of seizures, characteristically occurs at a very high blood lead level (>100 μg per deciliter [4.8 μmol per liter] in adults). With long-term low-level exposure, neurologic manifestations may be more insidious and can include memory impairment and irritability. Basophilic stippling of erythrocytes is a characteristic finding in cases of lead poisoning, but it can also be associated with arsenic poisoning, sideroblastic anemia, myelodysplastic syndrome, thalassemia, and other conditions.
A: Chelation therapy with succimer or calcium disodium EDTA is indicated for patients with a blood lead level above 80 μg per deciliter (3.9 μmol per liter). Depending on the duration of lead exposure and symptoms, such therapy may also be indicated for patients with lower blood lead levels; involvement of a toxicologist or an occupational and environmental medicine physician is useful in decision making. Once chelation therapy is initiated, patients are monitored closely for potential side effects, including hepatic and renal impairment, as well as transiently worsening symptoms due to the mobilization of lead from tissue and bone into the blood. The magnitude of reduction in symptoms is variable; such changes may occur over the course of several weeks or substantially longer (more than a year). Given that the removal of lead from the central nervous system is a slow process, neurocognitive effects may resolve slowly and incompletely, and there is concern that cumulative lead exposure may accelerate age-related cognitive decline.