A 3-year-old boy arrives to the emergency department after having suffered a seizure. The family reports that they had moved to Baltimore from the Midwest 3 months ago. The child was the product of a normal pregnancy and delivery, and he had experienced no medical problems until the move. The parents report that he has developed emotional lability, abdominal pain, “achy bones,” and intermittent vomiting and constipation. They initially attributed his behavior to the move and to the chaos in their house, which is being extensively renovated.
What is the most likely diagnosis?
What is the best test to diagnose this condition?
What is the best therapy?
ANSWERS TO CASE 28: Lead Toxicity
Summary: A 3-year-old, previously healthy child now living in a home undergoing extensive renovation has developed seizures, neurologic changes, and abdominal complaints.
• Most likely diagnosis: Lead toxicity.
• Best test: Blood lead level (BLL).
• Best therapy: Remove child from lead source and initiate chelation therapy.
1. Understand the signs, symptoms, and treatment of lead poisoning.
2. Be familiar with the environmental sources of lead.
3. Understand the sources of other environmental exposures.
This child is demonstrating signs and symptoms of lead poisoning. He may have been exposed to dust in the environment, or he may have displayed pica (the eating of nonfood substances such as paint chips, dirt, or clay). Therapy can be initiated immediately while awaiting the blood lead level. During the evaluation and treatment, other children in the home must be screened for elevated lead levels as well.
Note:Lead exposure sources vary across the United States. In the northeastern United States, older homes undergoing renovation are common sources of exposure. Leaded paint is far less common in other parts of the country. A complete investigation includes a travel history and an accounting of lead exposures through hobbies (such as stained glass), home renovation, welding, radiator repair, furniture refinishing, and similar activities.
CHELATING AGENT: A soluble compound that binds a metal ion (in this case lead) so that the new complex is excreted in the urine.
PLUMBISM: Alternate name for lead poisoning.
The incidence of lead poisoning in the United States has decreased dramatically over the last 20 years. Previous sources (gasoline, foods, beverage cans) have been eliminated; lead-containing paint in older homes is now the major source. Less common sources include foodstuffs from countries where regulations are not strict, glazed pottery, ingestion of leaded items (jewelry, fishing equipment), and exposure through burning of lead-containing batteries or through hobbies involving lead smelting. Several lines of toys were recalled by the US Consumer Product Safety Commission in 2010 when they were found to be coated with lead-based paint.
The signs and symptoms vary from none (especially at lower lead levels) to those listed in this case. However, symptoms may be seen at low blood lead levels (BLLs), and a child with very high BLLs occasionally may be asymptomatic. Anorexia, hyperirritability, altered sleep pattern, and decreased play are commonly seen. Developmental regression, especially with speech, may also be present.Abdominal complaints (occasional vomiting, intermittent pain, and constipation) are sometimes noted. Persistent vomiting, ataxia, altered consciousness, coma, and seizures are signs of encephalopathy.Permanent, long-term consequences include learning and cognitive deficits and aggressive behavior; with less lead in the environment and decreasing average lead levels, these more subtle findings are now more common than acute lead encephalopathy.
The BLL is the diagnostic test of choice, and demonstrates recent ingestion; however, a significant amount of lead is stored in other tissue, most notably bone. BLL, then, does not accurately reflect total body lead load. Other tests (free erythrocyte protoporphyrin, basophilic stippling, glycosuria, hypophosphatemia, long bone “lead lines,” and gastrointestinal tract radiopaque flecks) in symptomatic patients are less specific.
Treatment varies depending on the BLL and the patient’s symptoms. Admission to the hospital, stabilization, and chelation are appropriate for symptomatic patients. Therapy for asymptomatic patients could involve simple investigation of the child’s environment, outpatient chelation, or immediate hospitalization (Table 28-1). Close contact with local health agencies is important; they usually are charged with ensuring that the child’s environment is lead-free.
Table 28-1 • SUMMARY OF RECOMMENDATIONS FOR CHILDREN WITH CONFIRMED (VENOUS) ELEVATED BLOOD LEAD LEVELS
Chelation in an asymptomatic child may consist of intramuscular calcium disodium ethylenediaminetetraacetic acid (CaEDTA) or more commonly oral meso-2,3-dimercaptosuccinic acid (DMSA, succimer). Hospitalized symptomatic patients are often treated with 2,3-dimercaptopropanol (British anti-Lewisite [BAL]) and CaEDTA. Fluid balance is tricky; urine output is maintained because CaEDTA is renally excreted, but encephalopathy may be exacerbated with overhydration.
Newer research has cast doubt on the utility of chelation therapy in children with lead levels less than 45 µg/dL. Lead levels do decrease acutely with chelation therapy, but affected children do not show improvement in long-term cognitive testing. In fact, the most recent literature suggests that there is no “safe” lead level; even lead levels less than 10 µg/dL have been shown to have a deleterious impact on neurocognitive development. This evidence places further importance upon the primary prevention of lead exposure in children.
Targeted BLL screening of at-risk children rather than universal screening is recommended. Questionnaires to assess the risk of lead exposure query the age of the home or day care center, the possibility of exposure to high-lead environments (battery recycling plant, lead smelter, etc), or environments in which others (siblings, playmates, etc) with elevated BLLs have been identified. Some state and federal programs, such as Early Periodic Screening, Diagnosis, and Treatment (EPSDT) and Healthy Kids, provide further guidance on lead screening.
28.1 A developmentally normal 2-year-old child is in your inner city clinic for a well-child check. As part of the visit, you obtain a blood lead level and a hemoglobin level in accordance with your state’s Medicaid screening guidelines. The following week, the state lab calls your clinic to report that the child’s blood lead level is 14 µg/dL. Appropriate management of this level should include which of the following actions?
A. Initiate chelation therapy.
B. Perform long bone radiographs.
C. Reassure the parents that no action is required.
D. Repeat the blood lead level in 3 months.
E. Report to the local health department for environmental investigation.
28.2 While evaluating the family in the previous question, you discovered a 3-year-old sibling with a lead level of 50 µg/dL. You reported the case to the local authorities and initiated chelation therapy. All lead sources in the home have since been removed (verified by dust wipe samples), and the parents do not work in occupations prone to lead exposure. After a course of outpatient chelation therapy, the 3-year-old’s lead level dropped to 5 µg/dL. Today, however, the child’s 3-month follow-up blood lead level is 15 µg/dL. At this point, appropriate management includes which of the following actions?
A. Initiate a course of inpatient parenteral chelation therapy.
B. Perform long bone radiographs.
C. Reassure the parents and repeat a blood lead level in 3 months.
D. Recommend the family move to another home.
E. Repeat a course of outpatient chelation therapy.
28.3 A term newborn infant is admitted to the Neonatal ICU after having a seizure in the Well Baby Nursery. Your examination reveals a microcephalic infant with low birth weight who does not respond to sound. In your discussions with the family, you discover this is the parents’ first child. They recount odd symptoms that have developed in the both of them in the last few months, including fine tremors in their upper extremities and blurry vision. They also note that they both can no longer smell their food and that it “tastes funny.” The mother notes that she has had trouble walking straight in the last few weeks, but she attributes that to her pregnancy. Which of the following environmental toxins is most likely to have caused these findings?
A. Inorganic arsenic salts
C. Methyl mercury
E. Polychlorinated biphenyls
28.4 A previously healthy 2-year-old boy is brought to the emergency department by ambulance after having a generalized tonic-clonic seizure at home. The mother reports that she put him to bed early the night before because she was having some friends over for a Bunco party. This afternoon when she awoke she found him wandering around the house, seemingly off balance, and he was “not acting right.” She called EMS as soon as he had his seizure. The responding paramedic reported that the child’s initial blood glucose was 15 mg/dL; after administration of lorazepam and a bolus of D10W he stopped seizing. Upon examination you find a heart rate of 110 beats/min, a respiratory rate of 20 breaths/min, a temperature of 37°C (98.6°F), and a blood pressure of 89/43 mm Hg. His pupils are reactive, and his funduscopic examination is normal. The rest of his examination is benign. Which of the following is the most likely cause of the seizure?
A. 3,4-Methylenedioxymethamphetamine (MDMA; “Ecstasy”) ingestion
B. Brain tumor
C. Ethanol ingestion
D. Exogenous insulin administration
E. Head trauma
28.1 D. The patient’s lead screen is mildly elevated. Appropriate management includes educating the parents about potential lead exposures in the environment as well as in the diet. A repeat level should be performed in 3 months. Chelation therapy is currently advised for patients with a blood lead level of 45 µg/dL and above. Environmental investigation is recommended in patients with a blood lead level of 20 µg/dL and above, or if levels remain elevated despite educational efforts. Long bone radiographs are not recommended at any blood lead level.
28.2 C. In this case, reassurance is appropriate. Lead deposits in bone, and chelation does not remove all lead from the body. After chelation is complete, lead levels tend to rise again; the source is thought to be the redistribution of lead stored in bone. Repeat chelation is only recommended if the blood lead level rebounds to 45 µg/dL or higher. Moving to another home is not necessary, assuming the health department successfully remediated their current home. Long bone radiographs are not recommended at any blood lead level.
28.3 C. Infants exposed in utero to methyl mercury may display low birth weight, microcephaly, and seizures. They also display significant developmental delay and can have vision and hearing impairments. Symptoms in children and adults include ataxia, tremor, dysarthria, memory loss, altered sensorium (including vision, hearing, smell, and taste), dementia, and ultimately death. Acute ingestion of arsenic causes severe gastrointestinal symptoms; chronic exposure causes skin lesions and can cause peripheral neuropathy and encephalopathy. Orellanine is a toxin found in the Cortinarius species of mushroom that causes nausea, vomiting, and diarrhea; renal toxicity may occur several days later. Polychlorinated biphenyls (PCBs) cross the placenta and accumulate in breast milk; exposure in utero is thought to cause behavioral problems in later life.
28.4 C. While all of the answers are situations or conditions that can be associated with seizure, ethanol ingestion is the most likely based on the history of a toddler with hypoglycemia poorly supervised with presumed access to alcohol after an adult party. An ingestion of MDMA can certainly cause seizure in a toddler but is usually associated with hypertension, dilated pupils, and hyperthermia. There was no evidence of trauma on exam, and the funduscopic exam did not suggest increased intracranial pressure. If insulin was in the home and Munchausen syndrome by proxy was suspected, simultaneous evaluation of serum insulin level and C peptide during an episode of hypoglycemia may help make the diagnosis.
Lead-containing paint in older homes is the major source of lead exposure in the United States.
Behavioral signs of lead toxicity include hyperirritability, altered sleep patterns, decreased play activity, loss of developmental milestones (especially speech), and altered state of consciousness. Physical symptoms include vomiting, intermittent abdominal pain, constipation, ataxia, coma, and seizures.
Chelation therapy in an asymptomatic child with elevated lead levels consists of intramuscular calcium disodium ethylenediaminetetraacetic acid (CaEDTA) or oral meso-2,3-dimercaptosuccinic acid (succimer). Hospitalized patients with symptomatic disease are often treated with 2,3-dimercaptopropanol (BAL) and CaEDTA.
American Academy of Pediatrics. Lead exposure in children: prevention, detection, and management. Pediatrics. 2005; 116:1036-1046.
Centers for Disease Control and Prevention. Interpreting and managing blood lead levels <10 µg/dL in children and reducing childhood exposures to lead. Advisory Committee on Childhood Lead Poisoning Prevention (ACCLPP). MMWR 2007; 56 (RR08):1-14, 16.
Centers for Disease Control and Prevention. Recommendations for blood lead screening of young children enrolled in Medicaid: targeting a group at high risk. Advisory Committee on Childhood Lead Poisoning Prevention (ACCLPP). MMWR 2000; 49 (No. RR-14):1-13.
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