A 48-year-old man presents to the clinic with a 3-week history of severe, colicky abdomina… — USMLE Step 2 CK

A 48-year-old man presents to the clinic with a 3-week history of severe, colicky abdominal pain, intractable constipation, and worsening fatigue. Over the past few months, he has also experienced difficulty concentrating and frequent headaches. He has a past medical history of mild asthma. He works as an independent contractor specializing in the renovation of historic homes, and is currently restoring a Victorian-era house built in the 1890s. Vital signs are temperature $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure $155/90 \text{ mm Hg}$ , pulse $82/\text{min}$ , and respirations $14/\text{min}$ . Physical examination reveals pale conjunctivae and a blue-gray line along the gingival margin. The abdomen is diffusely tender to deep palpation without rebound or guarding. Neurologic examination shows weakness in right wrist extension.

Laboratory studies reveal:

Test	Value
Hemoglobin	$9.6 \text{ g/dL}$
Mean corpuscular volume	$74 \text{ fL}$
Leukocyte count	$6,800/\text{mm}^3$
Platelet count	$240,000/\text{mm}^3$

A peripheral blood smear shows erythrocytes with coarse basophilic stippling. Which of the following is the most appropriate next step in management?

Measurement of venous blood lead levelAnswer
B
Admission for nasogastric decompression and serial abdominal examinations
C
Assessment of thyroid-stimulating hormone and free T4 levels
D
Intravenous administration of broad-spectrum antibiotics
E
Prescription of a short-acting beta-agonist and oral corticosteroids

Answer

Measurement of venous blood lead level

Measurement of venous blood lead levels is the most appropriate next step because it confirms the diagnosis of lead poisoning. This patient's presentation of colicky abdominal pain, constipation, fatigue, extensor muscle weakness (wrist drop), and a blue-gray gingival margin (Burton line) is classic for heavy metal toxicity. His work restoring historic homes places him at high risk for inhaling or ingesting lead-based paint dust. Furthermore, the laboratory findings of microcytic anemia with basophilic stippling strongly support the diagnosis. Venous blood testing is required to accurately quantify the lead burden and determine the clinical threshold for initiating chelation therapy.

Step-by-Step Solution

Identify the patient's key clinical features.

The patient presents with severe abdominal pain, constipation, fatigue, wrist drop, a gingival blue-gray line, microcytic anemia, and basophilic stippling.

Synthesizing the physical and laboratory findings is essential to recognize a specific toxidrome.

Correlate clinical findings with occupational history.

The patient restores historic homes built before 1950, which heavily exposes him to lead-based paint dust. This directly accounts for all presenting symptoms.

Occupational exposures often provide the definitive context for toxicologic diagnoses.

Determine the appropriate diagnostic test for the suspected condition.

Measurement of a venous blood lead level is the gold standard to confirm heavy metal toxicity before initiating targeted therapy.

Clinical suspicion must be confirmed with quantitative blood levels to guide appropriate management such as chelation.

Key Concept

Adult lead toxicity frequently presents with abdominal colic, constipation, fatigue, peripheral neuropathy (such as wrist drop), and microcytic anemia with basophilic stippling. The diagnosis is definitively confirmed via venous blood lead levels.

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