Case Presentation: A 30 year old M truck driver with a history of herniated disc was referred to the emergency room (ER) by an infectious disease specialist for elevated eosinophils (12.96 K/uL), chest pain (CP) and tachycardia. The patient complained of pleuritic left sided CP without shortness of breath or hemoptysis. Six weeks prior to presentation, he had traveled to the Dominican Republic (DR) where he stayed at a resort and ate various food. He reported watery diarrhea (6x/day) without fevers, chills, or abdominal pain. He also started to experience throbbing bitemporal headaches associated with intermittent blurry vision without nausea or vomiting. Upon presentation to the ER, he was afebrile, HR 102 bpm, BP 120/80 mmHg, O2 sat 99% on room air. Labs were significant for leukocytosis (32.49 K/uL) with 50% eosinophils (16.25 K/uL), elevated IgE (351 KU/L) and transaminitis (peak AST/ALT: 287/718). CT angiogram of the chest showed acute pulmonary embolism (PE) in the left upper lobe artery. The patient was started on therapeutic anticoagulation. Infectious workup for Schistosomiasis (Ab), Coccidioides (Ab), Histoplasma (Ag), Strongyloides (Ab) and Trichinella (Ab) were negative. GI PCR revealed Enteroaggregative Escherichia Coli (EAEC). Autoimmune workup was negative. MRI/MRA of head, orbits, and neck was unrevealing. CT abdomen/pelvis showed prominent bilateral inguinal lymph nodes (largest: 1.6×1.3cm). Bone marrow biopsy was negative for JAK-2 and was consistent with trilineage hematopoiesis with eosinophilia. He refused a liver biopsy. Ten days after admission and after five repeat ova and parasites (O&P), his fifth O&P was positive for blastocystis hominis (BH). Metronidazole was initiated with significant improvement of eosinophilia and six months later patient’s eosinophilia completely resolved.
Discussion: This patient’s signs and symptoms point to a broad differential diagnosis including infectious, malignancy, and rheumatological disorder. Given the patient’s travel history and diarrhea, a parasitic infection was most likely. After extensive infectious workup including four negative O&P, flow cytometry, and finally, bone marrow biopsy was performed; which were unremarkable for any primary hematological disorders. His diarrhea resolved on day four of hospitalization. However, when his diarrhea re-occurred with persisting eosinophilia, a fifth O&P was sent and revealed BH. A parasitic infection should remain high on the differential when initial infectious workup, subsequent rheumatological, and malignancy workup are unrevealing. A negative O&P result does not rule out parasitic infection. Some parasites, including BH, shed periodically  and a single O&P only gives ~60% detection rate, while three O&P increases the probability to > 95% . In light of four negative O&P, the patient’s travel history, persistent diarrhea, and eosinophilia should keep a parasitic infection on the differential and should not deter clinicians from repeating multiple O&P.
Conclusions: This patient’s PE, headaches, and periodic blurry vision were initially attributed to eosinophilia with a presumed primary hematological disorder causing a hypercoagulable state; and diarrhea due to EAEC. Despite negative parasitic workup with unresolving diarrhea and eosinophilia, parasitic infection should still remain on a clinician’s differential. Although many diseases can occur in a patient at once, this case highlights the importance of tying together all signs and symptoms to reach a unifying diagnosis.