Zoanthid corals are commonly kept in home aquariums. They produce a potent palytoxin that has various neurologic effects, including paresthesia, weakness, and respiratory depression. We report on the case of a previously healthy male who handled a zoanthid coral in his aquarium and had subsequent bilateral lower extremity weakness. His symptoms resolved after supportive treatment of oral potassium replacement and intravenous fluids.

The Case

A previously healthy 34-year-old male presented to the emergency department with bilateral lower extremity weakness. He was able to walk when he woke up that morning but then was unable to stand without support. The day before presentation, the patient was moving a zoanthid coral with his bare hands. He denied any injury from the coral, but he had superficial lacerations on his hands from yard work. He denied tick exposure, camping, pets, recent travel, fever, illness, previous medical history, and personal/family history of neuromuscular or rheumatologic disorders. His physical exam showed inability to flex his bilateral quadriceps, with 4/5 strength on plantar and dorsiflexion of ankles and knees. He had equal sensation bilaterally, including the anterior thighs. There were no obvious injuries. CT of the brain and cervical spine were negative. Labs showed a potassium of 2.7. He was admitted to the hospital following a negative MRI. He received oral potassium and intravenous fluids with resolution of his weakness. Neurology suspected hypokalemic periodic paralysis (HPP). The patient was discharged with neurology follow-up.

Discussion

Zoanthid corals are often kept in home aquariums and produce a deadly vasoconstrictor called palytoxin. The toxin binds Na+/K+ ATPase and destroys the ion gradient across cell membranes, leading to cell death. Doses as low as 0.033 mcg/kg can be lethal. Case reports and anecdotal forums show that most exposures come from inhalation or skin contact. There are currently no guidelines for proper protective gear for handling these corals. There is no known antidote, and treatment is supportive.¹

A 2015 Morbidity and Mortality Weekly Report from the Centers for Disease Control and Prevention shows that palytoxin exposure may cause nausea, headache, renal failure, weakness, ataxia, fever, and other symptoms.² These cases were seen in Alaskan aquarium shops and homes after individuals handled the coral without protective gear. Multiple aquarium store employees, along with all the residents of a home who were exposed to the coral, developed symptoms that mostly resolved by the following morning.

“Doses as low as 0.033 mcg/kg can be lethal. Case reports and anecdotal forums show that most exposures come from inhalation or skin contact. There are currently no guidelines for proper protective gear for handling these corals. There is no known antidote and treatment is supportive.”

There are various other case reports of palytoxin exposure. One case was that of a 25-year-old female who handled a zoanthid coral from her home aquarium and subsequently developed perioral paresthesia and dysgeusia (alteration of the sense of taste) that lasted for several days. She was treated with corticosteroids and antihistamines.³ Another case involved a patient who experienced dizziness, generalized weakness, myalgias, electrocardiogram abnormalities, and rhabdomyolysis. The symptoms resolved after supportive treatment with intravenous fluid.⁴

Though the neurology team suspected HPP in our patient, it is unlikely that this would have a first-time onset at 34 years of age. HPP begins in the teenage years and may manifest as several attacks per week. It may be precipitated by rest after exercise, stress, or a high-carbohydrate meal. Our patient was healthy and exercised regularly. It was unlikely for him to suddenly develop HPP if there were no changes to his routine. The only change was the exposure to the coral.

Conclusion

It is easy in a busy emergency department to attribute a patient’s symptoms to more common diagnoses. However, it is important to develop a broad differential and to obtain a detailed history. In our case, asking about the patient’s pets revealed his exposure to zoanthid coral. There are no current guidelines on proper handling to avoid exposure to palytoxin. Warning signs may help with educating the general public about the corals. However, proper handling techniques need to be established to prevent future exposure.

Dr. Zhao is an emergency medicine resident at Wright State University in Dayton, Ohio.

Dr. Ballester is program director and assistant professor of emergency medicine at Wright State University in Dayton, Ohio.

References

1. Hilgemann DW. From a pump to a pore: how palytoxin opens the gates. Proc Natl Acad Sci U S A. 2003;100(2):386-388.
2. Hamade AK, Deglin SE, McLaughlin JB, et al. Suspected palytoxin inhalation exposures associated with zoanthid corals in aquarium shops and homes–Alaska, 2012-2014. MMWR Morb Mortal Wkly Rep. 2015;64(31):852-855.
3. Nordt SP, Wu J, Zahller S, et al. Palytoxin poisoning after dermal contact with zoanthid coral. J Emerg Med. 2011;40(4):397-399.
4. Hoffmann K, Hermanns-Clausen M, Buhl C, et al. A case of palytoxin poisoning due to contact with zoanthid corals through a skin injury. Toxicon. 2008;51(8):1535-1537.