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3. Neurotoxic shellfish poisoning
Although all of these diagnoses are possible, neurotoxic shellfish poisoning is the most likely given recent trip to New Orleans. Neurotoxic shellfish poisoning (NSP) is associated with "red tides" along the southeastern coast of the US, Gulf of Mexico and the Caribbean. Marine dinoflagellates (Karenia brevis) produce neurotoxins and hemolytic toxins collectively called brevetoxins. Eating contaminated shellfish is the most common form of NSP with immediate symptoms up to 24 hours post ingestion. Symptoms usually resolve within 24 hours but can last up to 72 hours (1). Presenting symptoms include nausea, vomiting, diarrhea, abdominal pain as well as facial and extremity paresthesias, vertigo, incoordination and convulsions. Another common symptom is temperature reversal, when patients experience alternating hot and cold sensations between the torso and lower extremities. For physicians in non-endemic areas, such as the Southwest, patients presenting with the odd constellation of sudden-onset gastrointestinal and neurological symptoms and temperature reversal should prompt close questioning of recent travel and dietary intake. The patient recovered with supportive care. Neurotoxic shellfish poisoning from brevetoxin was the presumed diagnosis due to the patient’s constellation of symptoms, recent travel, and dietary history.
Acute porphyria is also possible given the highly variable presentation of this disease often presenting with acute abdominal pain in acute attacks accompanied by nausea, vomiting, sensory and motor neuropathies. The autonomic nervous system is commonly affected with patients presenting with hypertension, tachycardia, diaphoresis and tremor which this patient did not have.
This patient's hyponatremia is likely explained by his excessive water intake but this does not explain the other symptoms. Metastatic small cell lung cancer with SIADH might explain these symptoms but is not likely given such acute onset in a previously healthy man. Recreational drug use could also explain these symptoms but is less likely than other diagnoses.
What is the most likely cause of his bradycardia in the ICU? (Click on the correct answer to be directed to the third of six pages)