Symptomatic cyanogenic glycoside exposure following consumption of cassava leaves purchased at a U.S. farmers market.

The cyanogenic potential of the cassava plant is well documented in both its roots and leaves. Unlike cassava root, fresh cassava leaves are unfamiliar to many United States (US) consumers and may be mistaken for edible leafy greens, creating a risk for inadvertent cyanide poisoning when sold without preparation guidance. We report two otherwise healthy adults who purchased unlabeled fresh greens described as cassava leaves (Manihot esculenta Crantz) at a San Francisco farmers market. The leaves, which contain cyanogenic glycosides, were consumed nearly raw. While chewing, the male developed oral numbness, prompting cessation of ingestion and online research of the plant. After contacting their regional poison control center, they were advised to seek emergency department evaluation and treatment. The patients presented with nausea, fatigue, malaise, and lightheadedness, and were treated with oral activated charcoal and fluids. Laboratory studies showed mild lactic acidosis (2.9 mmol/L and 2.7 mmol/L in the female and male, respectively), which resolved after crystalloid hydration. The case was reported to city public health authorities, who referred the case to county and state agricultural authorities. This resulted in vendor education and mandatory point-of-sale labeling with preparation guidance. This case demonstrates that cassava-related cyanide toxicity can occur in the US, as fresh products enter markets through informal channels without guidance. It underscores the need for vendor education and labeling, regulatory oversight, emergency department clinician awareness, and the importance of clinician reporting to help prevent future exposures.