SHM Converge Scientific Abstract ePoster Gallery-Serotonin Syndrome Masquerading as Cannabinoid Hyperemesis Syndrome in a Young Adult: A Case Report

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This case report describes a 26-year-old man with depression and anxiety taking fluoxetine and using daily cannabis who repeatedly presented with intractable vomiting and was initially presumed to have cannabinoid hyperemesis syndrome (CHS). During the admission, he also had paroxysmal tachycardia, agitation, leukocytosis, hypokalemia, lactic acidosis, and elevated CPK. A focused neurologic exam revealed rotary nystagmus, hyperreflexia, rigidity, and inducible ankle and jaw clonus, which shifted the diagnosis from CHS to serotonin syndrome (SS) using Hunter criteria.<br /><br />The report emphasizes that SS can be mistaken for CHS because both may present with vomiting, diaphoresis, anxiety, and autonomic instability. Diagnostic anchoring on cannabis use can delay recognition of serotonin toxicity, especially when clinicians do not perform a neuromuscular exam. In this case, the patient had received haloperidol and metoclopramide in the ED, medications that may worsen serotonergic toxicity. Fluoxetine, with its long half-life and active metabolites, can rarely cause SS even as monotherapy.<br /><br />After fluoxetine was stopped, the patient’s symptoms resolved within 24 hours and his hospital course was uncomplicated. The authors stress the importance of considering SS in patients with recurrent vomiting, agitation, or tachycardia—particularly when neurologic findings such as clonus, hyperreflexia, or nystagmus are present. They also note that other mimics include cocaine or amphetamine toxicity and severe alcohol withdrawal, with urine toxicology potentially helpful in differentiation.<br /><br />Overall, the case highlights the need for a high index of suspicion for serotonin toxicity and a careful neurologic assessment to avoid premature closure when evaluating patients with suspected CHS.

Asset Subtitle

Ayesha Khan

Meta Tag

Author List Ayesha Khan, Maykl Mosheyev, Nicholas Mulchan, Sohaib Agha, Stephanie Basant, Tommy Ojukwu Perdomo

Category Clinical Vignettes

Concept Serotonin Syndrome

Concept Cannabinoid Hyperemesis Syndrome

Concept Autonomic Instability

Concept Altered Mental Status

Concept Hyperreflexia

Distinguished Non-Finalist

Presenter Organization Department of Medicine, NYU Langone Hospital – Suffolk, Patchogue, NY

Presenting Author Ayesha Khan

Track Adult

Keywords

serotonin syndrome

cannabinoid hyperemesis syndrome

fluoxetine

vomiting

clonus

hyperreflexia

nystagmus

autonomic instability

Hunter criteria

cannabis use

Serotonin Syndrome

Cannabinoid Hyperemesis Syndrome

Autonomic Instability

Altered Mental Status

Hyperreflexia