Fugu poisoning is a term encompassing ingestion of pufferfish (termed fugu) that contains tetrodotoxin, a very potent neurotoxin that can be fatal in sufficient concentrations. Patients initially present with paresthesias and gastrointestinal irritation, followed by progressive paralysis, hypotension, loss of consciousness and cardiac arrest with respiratory muscle paralysis. The diagnosis is made after identifying recent consumption of pufferfish and observation of typical signs and symptoms. When possible, laboratory evaluation of tetrodotoxin levels in the blood may be implemented.
Ingestion of pufferfish (called fugu or "river pig" in Japanese), considered to be one of the most delicious fish in Japan, can lead to life-threatening intoxication that is often described in the literature as fugu poisoning [1] [2] [3]. The pathogenesis stems from the presence of tetrodotoxin (TTX) in the internal organs of the fugu (the liver, the intestines, and gonads, but also the skin), a powerful heat-stable neurotoxin that blocks sodium channel action, thus diminishing neuronal activity [1] [4]. In most cases, the onset of symptoms appears shortly after ingestion of the toxin (<30 minutes) [1], with initial signs being gastrointestinal complaints (nausea, vomiting) and mild paresthesia of the perioral area [2] [3]. As the activity of TTX increases, paresthesia and weakness spread to the chest and both upper and lower extremities, whereas headaches, vertigo, ataxia, and blurred vision also appear [2] [3] [4]. Other common complaints are diaphoresis, dysphagia, excessive salivation, seizures, and muscle spasms, whereas hypotension, bradycardia, and fixed dilated pupils are markers of severe poisoning [2] [4]. Respiratory difficulties, arising from progressive paralysis of the breathing muscles, develop in advanced stages, and can be fatal within 24 hours [3] [4]. In fact, fatality rates of severe fugu poisoning are estimated at 60% according to certain reports [4].
Because of the high fatality rate of fugu poisoning, a prompt diagnosis could be life-saving. For this reason, the physician must conduct a thorough physical examination, and most importantly, obtain a detailed patient history, which is perhaps the vital step in the workup [3] [4]. Fugu poisoning has been reported mainly in countries of Southeast Asia (Bangladesh, Taiwan, Cambodia, Hong Kong), but cases in the United States were also described in the literature [3] [4] [5] [6]. Very recent ingestion of pufferfish should be disclosed during the interview, whereas a complete neurological assessment provides sufficient clues to make a presumptive diagnosis of a sudden and progressive paralysis. Since several outbreaks have occurred in association with TTX from fugu [1], physicians must check if similar symptoms are present in friends or persons who ate the same food. The diagnosis of fugu poisoning rests on clinical grounds, but when possible, levels of TTX can be measured in the patient's serum or urine (or in leftover food, if available) [3] [4] [6] [7]. Mass spectrometry (MS) is able to detect tetrodotoxin in these samples and confirm the diagnosis [7].