Lead poisoning has been described in older children and adults with developmental delays or autism spectrum disorder who have pica behavior and ingest lead paint.

Teaching Topic 

A Diagnosis to Chew On 

CLINICAL PROBLEM-SOLVING 

A Diagnosis to Chew On 

R.H. Goldman and L. Weissmann

  

Lead poisoning has been described in older children and adults with developmental delays or autism spectrum disorder who have pica behavior and ingest lead paint.

Clinical Pearls

  Describe the anemia associated with lead poisoning.

Anemia associated with lead poisoning can be normocytic or microcytic; it is attributed to several mechanisms, including impaired heme synthesis, shortened survival of erythrocytes (hemolysis), and impaired renal production of erythropoietin. Anemia develops when blood lead levels exceed 50 to 60 μg per deciliter.

  Does lead cross the placenta?

Lead crosses the placenta. Asymptomatic elevated lead levels in pregnant women pose risks with respect to pregnancy outcomes (e.g., gestational hypertension and spontaneous abortion) and fetal development (e.g., developmental delays, reduced IQ, and behavioral problems).

Morning Report Questions

Q. What are some of the features of lead poisoning?

A. Lead is a multisystem toxicant that has dose-related effects on the blood, the brain, and the cardiovascular, renal, and reproductive systems. Iron deficiency is associated with increased absorption of lead. In adults, colicky pain can occur when blood lead levels exceed approximately 80 μg per deciliter, whereas milder, nonspecific gastrointestinal discomfort and constipation occur with levels higher than 60 μg per deciliter, and myalgias with levels higher than 40 to 50 μg per deciliter. Colic and anemia resolve when the blood lead level declines. In contrast, both acute lead poisoning and chronic lead exposure can lead to long-term health effects, including irreversible cognitive and renal impairments, and an increased risk of hypertension and cardiac death. Mild elevations of blood lead levels are typically asymptomatic, yet they are also associated with long-term toxic effects, which underscores the need to proactively identify and reduce lead exposures. Most lead is excreted in the urine; it has a half-life of 1 to 2 months (without chelation therapy), and the nonexcreted portion is stored in bone for decades. Basophilic stippling is a nonspecific and inconsistent finding in patients with lead poisoning.

Q. When is chelation therapy for elevated lead levels indicated in adults?

A. Chelation therapy is generally advised in adults when blood lead levels are higher than 80 μg per deciliter. Chelating agents include calcium disodium EDTA and meso 2,3-dimercaptosuccinic acid (DMSA, also called succimer, a less toxic analogue of dimercaprol). Both agents enhance urinary excretion of lead and lower blood lead levels. DMSA is approved by the Food and Drug Administration for treatment of lead poisoning in children; it is also used widely and is safe in adults. Although there are anecdotal reports that chelation therapy relieves acute symptoms, there is a shortage of controlled trials in adults to show a reduction in long-term adverse effects.

Table 1. Potential Sources of Lead Exposure in Adults.