Puss Caterpillar Envenomation: Erucism Mimicking Appendicitis in a Young Child

A 4-year-old female presented to the emergency department with 2 days of abdominal pain, nausea, and vomiting. She was tachycardic and had abdominal tenderness. Laboratory studies revealed a leukocytosis, hypokalemia, and metabolic acidosis. Her Pediatric Appendicitis Score (MDCalc) was calculated as 6, indicating that appendicitis could not be excluded. She was transferred to our pediatric hospital for further evaluation. Her ultrasound at our facility was normal. Upon reexamination, the patient was noted to have a red mark on her left index finger, and the family reported that the patient may have been stung by a puss caterpillar before the onset of her symptoms. The patient was treated with ondansetron, morphine, and intravenous fluids, and her symptoms resolved. Erucism frequently develops after stings from the puss caterpillar, which can be found through the southern United States. The most consistent clinical feature is pain. Numbness, muscle cramping, paresthesias, nausea, vomiting, and chest pain have also been described. Severe abdominal pain is reported rarely and may be mistaken for peritonitis. Analgesia is the mainstay of treatment. Topical icepacks have demonstrated inconsistent benefit in relieving pain. Oral medications, including acetaminophen, nonsteroidal anti-inflammatory drugs, and, rarely, opioids, typically suffice. Severe envenomations may require parenteral narcotics.