A Lesion in the Lungs: Primary Pulmonary Echinococcosis

Echinococcus is a species of cestode that can cause disease in humans. Human echinococcus is caused by infection in the larval stage and most often manifests as hydatid liver cysts in the adult population.1Centers for Disease Control and Prevention (CDC). CDC - Echinococcosis - Biology. Available at: https://www.cdc.gov/parasites/echinococcosis/biology.html. Accessed August 21, 2020.Google Scholar,2Morar R Feldman C Pulmonary echinococcosis.Eur Respir J. 2003; 21: 1069-1077Crossref PubMed Scopus (179) Google Scholar Although cyst formation can occur in other organs such as the lungs, extrahepatic disease generally develops as a secondary infection following hematogenous seeding. We present an unusual case of primary pulmonary echinococcosis without evidence of liver involvement. A previously healthy 28-year-old Armenian female was referred to the emergency department after an outpatient computed tomography (CT) thorax revealed an 8.5 × 4.5 cm right middle lobe (RML) cavitary lesion with an air-fluid level (Figure). Aside from a chronic cough with recent development of sputum production, she was otherwise asymptomatic. She denied substance use or animal exposures. On presentation, she was febrile to 39.2°C and tachycardic to 140 beats per minute with an unremarkable physical examination. Complete blood count (CBC) showed leukocytosis 14.7 K/cmm with neutrophilic predominance and elevated absolute eosinophils 2.8 K/cmm. Basic chemistry and hepatic panels were normal. Blood, sputum, and stool cultures as well as tests for tuberculosis, cryptococcus, coccidiodes, aspergillosis, and HIV all resulted negative. A bronchoscopy with alveolar lavage was performed, and the patient was discharged with a 6-week course of antibiotics for empiric treatment of lung abscess. Bronchoalveolar lavage (BAL) revealed numerous eosinophils, foamy pulmonary macrophages, and rare multinucleated giant cells. Daily prednisone of 40 mg was prescribed outpatient for chronic eosinophilic pneumonia. Three weeks later, the patient returned with new shortness of breath and right chest pain. A stat chest X-ray revealed a large pneumothorax with tension physiology, and a chest tube was placed emergently. Steroids were tapered off with resultant increase in the peripheral eosinophil count; however, the air leak persisted. CT of the abdomen was normal without intra-abdominal pathology, favoring a primary pulmonary eosinophilia. Thoracic surgery proceeded with a video-assisted thoracoscopic surgery lobectomy and cavitary lesion resection, intraoperatively noting a 4 cm RML white cyst cavity and thick visceral pleural gelatinous rind. The echinococcus immunoglobulin G (IgG) antibody subsequently returned positive and an acellular cyst wall suggestive of echinococcus was reported on the finalized surgical pathology. The patient was treated with albendazole and a CT of the thorax 2 months later showed no evidence of infectious recurrence. One of the major challenges to diagnosis in this patient was the absence of hepatic involvement in a diagnosis classically associated with the liver. Human contraction of echinococcus occurs through the fecal-oral route, typically through ingestion of eggs from contaminated produce or water. Once embryos are released from the eggs, they penetrate the intestinal wall and enter the portal circulation where most attach and form lesions in the liver.3Borrie J Gemmell MA Manktelow BW An experimental approach to evaluate the potential risk of hydatid disease from inhalation of echinococcus ova.Br J Surg. 1965; 52: 876-878Crossref PubMed Scopus (15) Google Scholar, 4Mao T Chungda D Phuntsok L et al.Pulmonary echinococcosis in China.J Thorac Dis. 2019; 11: 3146-3155Crossref PubMed Scopus (2) Google Scholar, 5Sarkar M Pathania R Jhobta A Thakur BR Chopra R Cystic pulmonary hydatidosis.Lung India. 2016; 33: 179-191Crossref PubMed Scopus (55) Google Scholar However, there are a few ways the larva can bypass the liver, resulting in a primary pulmonary infestation. Smaller embryos may circulate past the hepatic sinusoids without latching and continue into the pulmonary vasculature.2Morar R Feldman C Pulmonary echinococcosis.Eur Respir J. 2003; 21: 1069-1077Crossref PubMed Scopus (179) Google Scholar Alternatively, the thoracic duct represents a major pathway bridging the intestines and lungs by which the larva can circumvent the liver completely.5Sarkar M Pathania R Jhobta A Thakur BR Chopra R Cystic pulmonary hydatidosis.Lung India. 2016; 33: 179-191Crossref PubMed Scopus (55) Google Scholar Lastly, there is also the potential for direct inhalation of eggs inducing pulmonary hydatid disease.3Borrie J Gemmell MA Manktelow BW An experimental approach to evaluate the potential risk of hydatid disease from inhalation of echinococcus ova.Br J Surg. 1965; 52: 876-878Crossref PubMed Scopus (15) Google Scholar The diagnosis of echinococcosis in a nonendemic region can be particularly difficult when the clinical presentation is atypical and mimics numerous other disease entities. Recognition of the capacity of echinococcus to present as a primary pulmonary lesion is crucial to timely initiation of appropriate therapeutics and interventions as well a favorable prognosis for the patient.