Winning Abstracts from the 2015 Medical Student Abstract Competition: A Classic Disease Often Forgotten in Modern America
First author: Andrea Gaspar, University of Texas Medical School at Houston, Class of 2015
Lead toxicity had become commonplace after the Industrial Revolution secondary to increased occupational and environmental exposure. Fortunately, awareness and regulation since the 1970's has vastly diminished lead exposure, making its toxicity a rarity. The following case emphasizes the importance of lead toxicity as a differential diagnosis in a patient with vague abdominal pain.
A 42-year-old woman presented to the emergency department with several months of diffuse abdominal pain, characterized as an intermittent "biting" sensation that had worsened over the past three days. She also experienced nausea, vomiting, and proximal lower extremity cramping. On physical exam, she was in moderate distress due to pain and had minimal cognitive impairment. Abdominal exam was notable for diffuse tenderness to palpation. Laboratory data was remarkable for microcytic anemia, with a hemoglobin of 8.4 gr/dl and an MCV of 72 fl/cell. Her chemistries revealed hypophosphatemia, hyponatremia, and hypokalemia. Abdominal Computed Tomography and transvaginal ultrasound were unremarkable. Peripheral blood smear revealed basophilic stippling. Protoporphyrin level was elevated at 286 µg/dL. The constellation of symptoms and laboratory findings suggested the diagnosis of chronic lead toxicity, which was confirmed with a blood-lead level > 65 µg/dL. Treatment consisted of aggressive electrolyte replacement and lead chelation with oral succimer. Within five days, abdominal pain, cognitive disturbances, and electrolyte abnormalities had resolved. Succimer was continued after discharge, for a total of fourteen days. Her house - a 1920s building - was identified as the lead source, and she moved to a new home. Upon follow up three months later, her lead levels had significantly decreased to 32.5 µg/dL, and she remained asymptomatic.
The prevalence of elevated lead levels in adults is only 6.4/100,000, a number that has decreased by fifty-four percent over the last eighteen years. Ninety-one percent of lead exposures are occupational. Although elevated lead levels are never considered safe, the classic symptoms of chronic lead toxicity appear between 30-70 µg/dL. The ionic properties of lead disrupt the normal physiology of numerous biological processes. This results in a disparate clinical presentation that can include abdominal colic, anemia, muscle cramps, constipation, peripheral neuropathy, nephrotoxicity, and cognitive disturbances. Coupled with lead toxicity's low incidence, these vague features make it a challenging diagnosis for modern clinicians. Treatment with chelation therapy can dramatically diminish these symptoms, and removal from the source of exposure can result in a permanent cure. Considering lead toxicity in patients with abdominal pain coupled with microcytic anemia and electrolyte derangements can minimize excessive testing and delays in therapy.