Teaching Case

A 31-year-old adult with shortness of breath and bilateral chest pain was admitted in emergency. The patient had a history of fever and chest pain for the last 3 months but no haemoptysis. He had a regular history of travelling abroad on and off. The chest X-Ray was done, which revealed bilateral pneumothorax. Due to a persistent decrease in saturation, a pigtail tube was inserted into the left pleural space. His white blood cell count was 26,700/mm3 with eosinophils-67%. A chest X-Ray 2 months prior to this episode with similar history of mild chest pain was normal. Then, HRCT chest was performed for further evaluation. Sputum samples were also sent from the emergency which revealed an ova of Paragonimiasis.

The chest X-ray showed bilateral pneumothorax (left > right) with single thin-walled cavitary lesion in the right middle zone. HRCT showed that a well-defined cavitary lesion was seen in the anterior segment of the right upper lobe. The cavity was thin walled with slightly irregular borders. Minimal fluid level was noted within the cavity in the dependent aspect. There was no evidence of calcifications, fat component or solid mural nodule within the cavity. Curvilinear track was noted in the supero-lateral aspect of the cavity, which extends from the pleural surface to the wall of the cavity. Patchy areas of consolidation were seen within the bilateral lower lobes. Minimal pneumothorax was seen on bilateral pleural space. A pigtail tube within the left pleural space was noted in situ. There was no evidence of mediastinal lymphadenopathy. Pericardium appeared to be normal.

Paragnomiasis is the important food borne parasitic zoonosis caused by trematodes of genus Paragonimus (its common name is lung fluke). It is found in tropical, subtropical and temperate climates. It is endemic in many parts of Asia, Africa and South America. Mammals are the definite host for Paragonimiasis (in which sexual reproduction occurs) and the snails and crustaceans are the intermediate hosts. Humans acquire infection from the ingestion of undercooked crustaceans containing metacercariae, the larval stage of the parasite. After ingestion, the larvae reaches the intestine and penetrates the intestinal wall to reach into the peritoneal cavity. In about 8 weeks it penetrates the diaphragm and pleura to reach the lung. The parasite resides within the lung of the definite host and the fertilised eggs are expectorated from the airway which easily hatch in the water. The released eggs get into the intermediate hosts which completes the life cycle of the parasite [1]. Initial clinical presentations of the disease can mimic pulmonary tuberculosis or lung cancer in the form of chest pain, haemoptysis and pleural effusion. In the region where people eat crabs or undercooked sea foods, this disease should be suspected with any clinical presentations of chest pain or haemoptysis. So, clinical features, lab parameters and image findings should be considered for proper diagnosis [2]. Imaging findings of Paragonimiasis can be divided according to pulmonary and extra pulmonary manifestations. In pulmonary findings, most of the patients have pleural thickening (75%) with pleural effusion because of long-standing pleural inflammation. Nodular lesions are seen in the peripheral aspect of the lung parenchyma (57%) as the parasite penetrates from the pleural surface. Sometimes, the nodules may be associated with linear tracks which can be a lead for the diagnosis of parasitic infestations; hydro pneumothorax can also be seen (12.5%). Other extra pulmonary findings could be in the form of pericardial effusion, lymphadenopathy around the internal mammary arteries, non-enhancing linear tracks within the liver and spleen, ascites and omental thickening [3]. The CT findings in Paragnomiasis in a study done by Im et al. showed round low attenuation lesions (5-15mm) filled with either fluid or gas and peripheral linear tracks suggestive of worn migration tracks [4]. Non-enhancing thin-walled cavity, absence of chronic lung fibrosis, bronchiectasis and lymphadenopathy differentiate it from pulmonary tuberculosis. Similarly, non-enhancing wall and absence of the mediastinal, as well as hilar lymphadenopathy, rules out the possibility of malignancy. Clinical features and blood investigations revealing peripheral eosinophilia with supporting image findings are the key for the diagnosis of Paragonimiasis. Serological testing for anti-Paragonimiasis antibody by ELISA is the most sensitive and specific for establishing the diagnosis [5]. Pulmonary Paragonimiasis is the diagnosis of exclusion in a developing country like Nepal and is important in order to differentiate between the other cystic or cavitary lesions of lung-like tuberculosis or lung carcinoma. Therefore, correlating with history, clinical findings as well as blood profile are equally important in the diagnosis and proper treatment of Paragonimiasis infestation.