In the latest Case Record of the Massachusetts General Hospital, a 59-year-old man was admitted to the hospital because of fatigue, abdominal pain, new anemia, arthralgias, abnormal liver function, and emotional lability. A peripheral-blood smear showed polychromasia and coarse basophilic stippling of erythrocytes.
Acute abdominal pain has a broad differential diagnosis that includes both intraabdominal and extraabdominal causes. Life-threatening intraabdominal catastrophes, such as gastrointestinal perforation, intestinal infarction, and a ruptured abdominal aortic aneurysm, cause illness within minutes or hours.
• What is the typical presentation of acute porphyria?
Porphyrias are generally inherited and are caused by a deficiency in the activity of one of the enzymes required for normal heme synthesis. Acute porphyria should be considered in a patient with acute, generally recurrent, severe abdominal pain that does not have a clear explanation. Features that are consistent with a diagnosis of acute porphyria include severe neuropathic abdominal pain, nausea, stress or restlessness, pain in the arms and legs, constipation, colonic pseudo-obstruction, tachycardia, episodic hypertension, and SIADH; characteristically dark urine is not present.
• What is the differential diagnosis for basophilic stippling?
Basophilic stippling is a hallmark of sideroblastic anemia and of lead poisoning, although it is not a constant feature of the latter. It is also seen in patients with arsenic poisoning, some thalassemias, a deficiency of erythrocyte pyrimidine 5′-nucleotidase, or thrombotic thrombocytopenic purpura.
Morning Report Questions
Q: What are the typical clinical features in lead poisoning?
A: Patients typically present with abdominal pain (“lead colic”), and may also report nausea, dysgeusia, and constipation. Other features consistent with lead poisoning are colonic pseudo-obstruction, joint and muscle pain, acute anemia, basophilic stippling, SIADH, and decline in the blood level of phosphorus (which may be due to renal phosphate wasting). Lead lines, or bluish pigmentation at the gum-tooth line caused by a reaction of lead with dental plaque, are not a reliable indictor of acute lead poisoning. Deposition of lead in bones may be seen with long-term exposure, as may hypertension and neuropsychiatric effects.
Q: How is a diagnosis of lead poisoning made?
A: A diagnosis of lead poisoning is confirmed by measuring the blood lead level; a level of 10 micrograms per deciliter or higher is considered elevated in an adult. The level may be higher than 100 micrograms per deciliter in patients with acute lead poisoning, which is much less common than chronic lead poisoning. Heme biosynthesis is impaired when 5-aminolevulinic acid (ALA) dehydratase is 80 to 90% inhibited; this occurs at a blood lead level of approximately 55 micrograms per deciliter. Lead inhibits many of the enzymes active in the heme biosynthetic pathway, including ALA dehydratase, coproporphyrinogen oxidase, and ferrochelatase, thereby leading to incorporation of zinc instead of iron into protoporphyrin IX (the immediate precursor of heme) and to accumulation of zinc-chelated protoporphyrin in erythrocytes, which is often reflected by an elevated level of zinc protoporphyrin.