A 23-year-old man comes to the emergency department due to 4 days of cramping abdominal pain. He has been feeling weak for the past 2 weeks. He tried over-the-counter antacids without relief. He is an industrial laborer with no significant medical history or known allergies. The patient's parents have hypertension, and his siblings are healthy. Temperature is 37.1 C (98.8 F). Physical examination is unremarkable. The patient's peripheral blood smear is shown on the image below. Which of the following is the most likely cause of this patient's symptoms?

Question

A 23-year-old man comes to the emergency department due to 4 days of cramping abdominal pain.  He has been feeling weak for the past 2 weeks.  He tried over-the-counter antacids without relief.  He is an industrial laborer with no significant medical history or known allergies.  The patient's parents have hypertension, and his siblings are healthy.  Temperature is 37.1 C (98.8 F).  Physical examination is unremarkable.  The patient's peripheral blood smear is shown on the image below.  Which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

11ec160b_3986_a7a3_9249_4788696ccb56_MD0001_00 This patient likely has lead poisoning. In the United States, lead poisoning (plumbism) is typically a pediatric condition that results from children ingesting lead-containing paint chips. However, lead poisoning can also occur in adults. Affected individuals are usually miners or industrial workers (especially those in battery manufacturing) who inhale particulate lead while working. Adults with lead poisoning present with weakness, abdominal pain, and constipation. In severe cases, there may be neurologic manifestations (eg, headache, cognitive symptoms, peripheral neuropathy). On physical examination, patients may have blue "lead lines" at the junction of the teeth and gingivae. The classic diagnostic finding on peripheral blood smear is coarse basophilic stippling on a background of hypochromic microcytic anemia. Basophilic stippling results from the abnormal degradation of ribosomal RNA (due to lead-induced inhibition of a nucleotidase). The hypochromic microcytic anemia results from inhibition of δ-aminolevulinate dehydratase (δ-ALA dehydratase) and the resultant reduced incorporation of iron into heme. The net effect of these defects is decreased hemoglobin synthesis. (Choice A) Acute intermittent porphyria can cause attacks of abdominal pain (without abdominal tenderness) due to autonomic neuropathy. Erythropoiesis is not affected, and the peripheral blood smear is normal. (Choice B) Myeloblasts containing cytoplasmic Auer rods on peripheral blood smear are a characteristic finding of acute myelogenous leukemia. (Choice C) The autoimmune destruction of gastric parietal cells and/or intrinsic factor cause atrophic (autoimmune) gastritis, which can lead to pernicious anemia due to vitamin B₁₂ malabsorption. (Choice E) Non-Hodgkin lymphoma can invade the bone marrow, causing myelophthisic anemia. A peripheral blood smear would show leukoerythroblastosis (immature granulocytes and nucleated teardrop-shaped erythrocytes). (Choice F) Malnutrition may lead to folate deficiency or, more rarely, vitamin B₁₂ deficiency. Deficiencies of either vitamin cause megaloblastic anemia, with hypersegmented neutrophils and large erythrocytes on peripheral blood smear. Educational objective: Coarse erythrocyte basophilic stippling and microcytic hypochromic anemia are common peripheral blood smear findings in lead poisoning. High-risk groups include young children ingesting paint chips and industrial workers inhaling particulate lead.

A 23-Year-Old Man Comes to the Emergency Department Due to 4