Toxicology – Lead Poisoning

Sources

Common sources of lead exposure include:

• Older lead-based paint and contaminated household dust
• Batteries
• Ceramics and pottery glazes
• Plumbing and contaminated water
• Certain toys, jewelry, figurines, and imported products
• Some traditional or nonstandard medicines
• Occupational or industrial exposure

Typical Presentation

A child living in an older home may present with:

• Developmental delay
• Learning difficulties
• Behavioral problems
• Fatigue
• Vague abdominal complaints

Chronic exposure is often subtle and may be discovered only after screening.

Clinical Features

Acute lead toxicity may cause:

• Nausea and vomiting
• Abdominal pain
• Diarrhea
• Hemolysis
• Acute kidney injury
• Severe neurologic toxicity in major exposures

Chronic lead toxicity may cause:

• Recurrent abdominal pain
• Constipation
• Fatigue
• Headache
• Cognitive and learning impairment
• Behavioral changes
• Anemia
• Peripheral neuropathy
• Motor weakness, including wrist drop

Children are particularly vulnerable to the neurodevelopmental effects of lead.

Mechanism of Action

Lead disrupts multiple cellular processes and can damage several organ systems, especially:

• Central and peripheral nervous systems
• Kidneys
• Bone and bone marrow
• Gastrointestinal tract
• Cardiovascular system

It also interferes with enzymes involved in heme synthesis, contributing to anemia.

Laboratory Findings

Diagnosis is based primarily on an elevated blood lead level.

Other possible findings include:

• Microcytic or normocytic anemia
• Basophilic stippling on peripheral blood smear
• Increased erythrocyte protoporphyrin in significant chronic exposure

These findings support the diagnosis but are not as specific as the blood lead concentration.

Characteristic Findings

Classic but less commonly seen findings include:

• Burton lines: blue-gray discoloration along the gingival margin
• Lead lines: dense metaphyseal bands seen on radiographs of growing bones in chronically exposed children

Management

The most important intervention is to identify and eliminate the source of exposure.

Chelation may be required for significant poisoning. Agents used include:

• Succimer (DMSA)
• Calcium disodium EDTA
• Dimercaprol in selected severe cases

The choice of chelator depends on the blood lead level, symptoms, and severity of toxicity. Severe neurologic toxicity requires urgent specialist management.

Key Points

• Children are especially susceptible to lead-related cognitive and developmental injury.
• Chronic poisoning may present with abdominal pain, constipation, anemia, and behavioral or learning problems.
• Basophilic stippling is a classic clue but is not diagnostic by itself.
• Treatment begins with removal of the exposure source.
• Chelation is reserved for sufficiently elevated blood lead levels or clinically significant poisoning.