An Unusual Case of Echinococcal Cyst in the Spleen: Diagnostic Challenges and Management Strategies.

Cystic echinococcosis (CE) is a rare parasitic infection characterized by a mass effect within organs depending upon the site of the cyst, with the liver being the most common. Its presentation is usually chronic and may remain asymptomatic for many years. The infection typically presents in patients who live in endemic areas, sheep farmers, or those who work with sheep herding dogs. This presentation in a 26-year-old female living in Salt Lake City, Utah, is rare. This case report serves to highlight a rare presentation of an echinococcal infection in a 26-year-old female who suffered from severe upper gastrointestinal pain, persistent cough, nausea, and vomiting. Diagnostic tests revealed a 13 cm cyst located in her spleen. After confirming the diagnosis via ELISA and Western blot, the cyst tested positive for . Despite the potential for cyst rupture and subsequent severe anaphylactic reaction necessitating emergent care, the limited incidence of echinococcal infections within the United States rendered this case a medical enigma with an uncertain diagnosis. This case emphasizes the critical role of biostatistics in diagnosing diseases with low incidence rates.