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Pulmonary Paragonimiasis Diagnosed by Fine Needle Aspiration Biopsy 3

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Running title: Paragonimiasis 5

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Neda Zarrin-Khameh, M.D., M.P.H., Deborah R. Citron, M.D., M.P.H., 9

Charles E. Stager, Ph.D., and Rodolfo Laucirica, M.D. 10

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Baylor College of Medicine Department of Pathology and Ben Taub General Hospital 13

Houston, Texas 14

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Address Correspondence: 22

Rodolfo Laucirica, M.D. 23

Baylor College of Medicine 24

Department of Pathology 25

One Baylor Plaza 26

Houston, Texas 77030 27

Phone: 713-873-3216 28

Fax: 713-873-3214 29

Email: rodolfol@bcm.tmc.edu 30

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Copyright © 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.J. Clin. Microbiol. doi:10.1128/JCM.02424-07 JCM Accepts, published online ahead of print on 2 April 2008

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Abstract 1

We report a case of paragonimiasis involving a 12-year-old Latin-American boy. The 2

diagnosis was made by fine needle aspiration biopsy of a pulmonary nodule. Identification 3

to species by morphometric analysis of the eggs indicated that the infection was caused by 4

Paragonimus mexicanus. 5

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Case Report 7

A 12-year-old boy with a two-year history of seizures, headaches and intermittent 8

hemoptysis presented to the Ben Taub General Hospital emergency room (ER) after a 9

cluster of five seizure attacks. The boy was from El Salvador, had been in the United States 10

for 14 months and had been treated with phenytoin for his seizures. On presentation his 11

head CT scan showed a calcified cystic lesion in the left anterior frontal area. The EEG was 12

abnormal with recurrent spica slow waves in the left temporal lobe and frontal spike of 13

slow wave. He was diagnosed with symptomatic localized epilepsy with secondary 14

generalized tonic/clonic seizures. He was started on tegretol and followed monthly by the 15

Neurology service. He had been seizure free for nine months when he presented to the ER 16

for a second time with two episodes of self-limited tonic-clonic seizure at school, each 17

lasting less than one minute. There was no loss of bladder or bowel control. The patient 18

reported a one-year-history of intermittent hemoptysis. His sputum was reported to be 19

blood-streaked with no gross blood. He had an occasional productive cough, but no 20

hematemesis, nasal congestion, chest pain or shortness of breath. He occasionally had fever 21

but no chills, or night sweats. The patient’s mother reported he has had a 20-pound weight 22

loss in the past year. No diarrhea was reported. His physical activity was normal and he did 23

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not complain of fatigue. Headaches had been worse over the past few months; therefore, he 1

had missed several days of school. The headaches were frontal, throbbing and associated 2

with photophobia. He was also complained of problems with visual acuity. He denied any 3

syncope, vomiting or persistent poor vision. His headaches were relieved with Tylenol. 4

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His physical examination was unremarkable. His laboratory investigation documented a 6

normal complete blood count with no eosinophilia. His metabolic panel was also normal. 7

His cerebrospinal fluid (CSF) had 4 white cells and no red cells; CSF culture was negative 8

for bacteria, fungus and viruses. Abdominal and pelvic CT scans were normal. His chest x-9

ray & CT scan showed multiple lung nodules measuring up to 2.2 cm, but no 10

lymphadenopathy (figure 1). Pulmonary angiography showed no evidence of hypervascular 11

tumor, or arteriovenous malformation. A head CT scan revealed a focus of 12

encephalomalacia in the left superior frontal gyrus involving the underlying white matter 13

and a 2-3 mm focal calcification. A CT-guided lung fine needle aspiration biopsy (FNAB) 14

showed abundant necrotic cellular debris surrounding numerous thick-walled parasite eggs 15

morphologically consistent with those of the trematode or lung fluke Paragonimus 16

mexicanus (figure 2). The specimen was sent to CDC where the identification to species 17

was confirmed. The patient was treated with six doses of 1200 mg of Praziquantel. He was 18

discharged on Tegretol. 19

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The patient has been followed for 5 years. He was admitted recently because of an 21

increased frequency of seizures. His head CT showed no change in the size of the cyst and 22

no enhancing brain lesion. 23

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-------------------------- 1

Discussion 2

Paragonimiasis is a zoonotic disease caused by the trematodes Paragonimus spp. Other 3

names of this disease are oriental lung fluke, endemic hemoptysis, Mason hemoptysis, 4

pulmonary distomiasism, and parasitic hemoptysis (11). An estimated 20 million people 5

are currently infected in Africa, Asia and the Americas (17). About 48 species of 6

Paragonimus have been described, but only 16 of these infect humans (2, 16), including 7

Paragonimus westermani in the Far East and Southeast Asia, Paragonimus africanus in 8

West Africa, Paragonimus mexicanus in Central and South America, and Paragonimus 9

kellicotti in North America (3). Adult flukes reside mainly in the lung, but ectopic 10

localizations such as lymph nodes, heart, mediastinum, adrenal glands and kidneys have 11

also been reported (11). P. westermani is the most common species infecting humans 12

causing pulmonary, pleuropulmonary and cerebral paragonimiasis (2, 16). P. kellicotit is 13

the second most common cause of diagnosed human cases and the endemic species in the 14

United States. 15

The life cycle of P. spp is complex, involving two intermediate and one definitive host 16

(11). The early developmental stages are carried through the snails of Pleuroceridae and 17

Thiaridae families. Over a period of 10-12 weeks they transform through sporocyst and 18

rediae stages, and eventually become cercariae. The cercariae leave the snail and through 19

water reach the second intermediate host, a crustacean like a fresh-water crab or crayfish 20

(2, 16). Here they develop into encysted forms (metacercariae) and human infection occurs 21

where these contaminated crustacea are eaten poorly cooked or raw (18). Metacercariae 22

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excyst in duodenum and within 1 hour pass through the intestinal wall into the peritoneal 1

cavity (15). After 3 to 6 hours they migrate into the abdominal wall and then through the 2

diaphragm into the pleura and lung tissue (15, 18), where they become encapsulated, 3

usually in pairs or triplets. It takes 65 to 90 days for the flukes to develop fully, although 4

the symptoms may begin earlier. Eggs are shed around the worm and with rupture of the 5

contents of the encapsulated cyst into bronchioles are excreted in the sputum or swallowed 6

and excreted in the feces. 7

Disease is caused by inflammation and fibrosis elicited by worms in the lung or ectopic 8

locations. Manifestations depend on the duration of infection and probably the intensity of 9

infection. Flukes and eggs initially elicit an acute inflammatory response, consisting 10

predominantly of eosinophils, which is followed by the formation of a fibrous capsule (15). 11

The cysts are 1.5 cm in diameter, and these may rupture into the bronchioles, extruding 12

blood, eggs, and inflammatory exudate. Several excretory-secretory (ES) and somatic 13

products from tissue-invading helminths have been related to the modulation of host’s 14

immune response, e.g. through the induction/inhibition of different host immune mediators 15

such as nitric oxide (NO) (7). NO plays an important role in many infectious diseases due 16

to both its direct effector function and its potent immunoregulatory properties (6). It has 17

been shown that ES products from P. mexicanus adult worms trigger NO production from 18

alveolar macrophages (1). Further studies are needed to reveal the exact effect of NO 19

production on the host immune system. Histologically, a fibrous and granulomatous 20

reaction may be seen in association with the eggs. Secondary bronchopneumonia is 21

common. Pleural involvement is common (15) and can cause an eosinophilic empyema that 22

can be confused clinically with tuberculosis. Long standing lesions exhibit fibrosis and 23

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decreased inflammatory response which may eventually calcify. Common ectopic locations 1

of flukes are the pleura, abdominal wall, viscera and brain. Brain involvement is 2

particularly a serious complication (15). The adult fluke is thick, ovoid, red-brown, and 3

with a rounded anterior aspect and a tapered posterior. It measures 7.5 to 12 mm in length 4

and 4 to 6 mm in thickness. It may live for 20 years(18). 5

The initial illness is characterized by diarrhea, abdominal pain, urticaria, fever, malaise and 6

eosinophilia that last from days to weeks when the immature flukes are migrating. As 7

larvae penetrate the diaphragm and migrate within the pleural cavity, pleuritic chest pain 8

may develop occasionally associated with pleural effusion and pneumothorax. Pulmonary 9

manifestations include dyspnea, cough, and hemoptysis. Leukocytosis with prominent 10

eosinophilia and transient pulmonary infiltrate occurs during this time. Signs and 11

symptoms due to involvement of ectopic locations can also be seen at this stage. 12

Later in the chronic stage when the adult worms reside in the lungs and produce eggs, the 13

patient may develop chronic cough, expectoration of rusty or pigmented sputum and 14

hemoptysis, as in our case. Dyspnea, chest pain, fever and constitutional symptoms are 15

found less frequently. Chest x-ray findings are variable, non-diagnostic. Localized or 16

multisegmental infiltrates, usually poorly defined, are most common, but nodular (as in our 17

case), cystic, cavitary, and ring shadow patterns are also found. Pleural effusion, empyema, 18

pleural thickening and calcification of lesion can also be seen. In contrast to tuberculosis, 19

apical lesions are not predominant, cavities are smooth and regular, and infiltrates are less 20

well defined. Although lung involvement alone appears to cause little mortality, morbidity 21

and mortality are significant with ectopic lesions. Acute involvement of the brain is 22

associated with sudden onset of neurologic symptoms, usually in the presence of 23

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pulmonary disease, as in our case. Chronic brain involvement occurs in up to 10% of 1

patients and is associated with seizure and long-term deficits (15, 18). Most lesions of 2

cerebral paragonimiasis are located in the posterior loci of the cerebral hemispheres 3

(parietal, occipital, and/or posterior temporal area), but, frontal lobe involvement is not 4

uncommon as it presented in this case. The brain stem, the cerebellum, and the spinal cord 5

are rarely involved. The radiological findings of cerebral paragonimiasis are variable, 6

depending on the evolutional stage of the cerebral infection. Diagnosis of cerebral 7

paragonimiasis, in the early stage is important because curative chemotherapy with 8

Praziquantel is possible. Today, CT and MRI are the imaging methods of choice in the 9

evaluation of the nature and extent of cerebral infection, as well as virtually all other 10

intracranial abnormalities (4, 5). In the chronic stage of cerebral paragonimiasis, the 11

granulomas may become calcified. The classical pattern of calcification is seen as 12

congregated multiple round nodular or cystic lesions (so-called soap-bubble or egg-shell 13

appearance) on plain skull radiographs (10, 13). 14

The pulmonary lesions are most commonly mistaken for tuberculosis (in some series in 15

about half the patients). Indeed, tuberculosis is common in countries where paragonimiasis 16

is endemic. The lesions of paragonimiasis are more peripherally located and much more 17

common in the mid and lower lung zones as opposed to the predominant apical location of 18

tuberculous cavities. In the chronic inactive stage of cerebral paragonimiasis, the calcified 19

lesions may be mistaken for cysticercosis, tuberculosis, or other chronic inflammations, 20

unless the characteristic conglomerate and soap-bubble appearances are identified on plain 21

film radiography, CT or MR imaging (5, 9). 22

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The eggs of Paragonimus spp may be mistaken for those of other operculate trematodes 1

including Clonorchis sinensis, which are much smaller (26-35 micron) and those of 2

Fasciola hepatica and Fasciolopsis buski, which are considerably larger (130-140 micron). 3

The eggs of Schistosoma japonicum are about the same size and shape, but schistosome 4

eggs lack an operculum, have thinner shells and are not birefringent (2, 15). 5

Diagnosis is established by detection of the characteristic ova in stool or sputum. The eggs 6

of Paragonimus spp are yellow to brown with a flattened operculum at one end. In 7

addition, as a result of their thick shell, the eggs are birefringent with polarized light (figure 8

2). Over time, the eggs may undergo calcification (18). The eggs of P. mexicanus measure 9

on average 80 x 40 microns. The intact eggs from our patient measured on average 79 x 48 10

microns. Egg size and geographic location of our index case are helpful in establishing the 11

species of Paragonimus involved in our patient’s infection (Table 1) (12). 12

Concentration techniques may be needed for detection of eggs in lightly infected patients 13

or those with suspected ectopic lesions. In acute disease, eggs may not be detected until 2 14

to 3 months after exposure (15). Serologic testing for anti-paragonimus IgG by ELISA has 15

a sensitivity of 100% and specificity of 91% to 100% (12). This test is mainly available at 16

Center for Disease Control and Prevention (CDC). 17

The intradermal test has been widely used, mainly for screening of patients in endemic 18

areas. A positive reaction does not always mean active infection and a test can remain 19

positive as long as 20 years after complete recovery. Praziquantel is the treatment of choice 20

at 25 mg/kg/day for 2 days; and it is usually given three times a day. The overall cure rate 21

is more than 90% (8, 14). In cases of cerebral lesions higher doses must be given but only 22

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under the protection of steroids to prevent epilepsy secondary to perilesional edema. Older 1

drugs like bithionol and niclofolan are also effective but more toxic (14). 2

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In summary, P. mexicanus is an uncommon cause of paragonimiasis in North America. 4

Infected patients are usually from South American countries or have travel history to South 5

America. The most common presentation is pulmonary involvement. Brain involvement 6

usually occurs in the presence of pulmonary lesions, and can cause a hemorrhagic lesion 7

and even death. Recognition of brain involvement in early stages is critical since it can be 8

treated with medication. In the late stages, brain lesions calcify and can cause seizures and 9

long-term deficit. Our patient displayed both pulmonary and cerebral lesions, and we were 10

able to establish the diagnosis via FNAB of one of the pulmonary nodules. 11

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References 13

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Velez, and A. Muro. 2005. Lung-migrating digenean parasites: in vitro influence 15

on nitric oxide production from normal rat pulmonary macrophages. Exp Parasitol 16

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Figure Legends 6 7

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Figure 1. CT scan of chest illustrating well defined lung nodules 9

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Figure 2. Paragonimus egg, composite photograph. The left panel shows an egg from the 12

aspiration biopsy where we see the characteristic thickened shell and slightly flattened end. 13

(Papanicolaou stain, x 400). The right side illustrates the birefringent Paragonimus egg; 14

this characteristic helps differentiate this parasitic egg from Schistosoma japonicum 15

(Papanicolaou stain, x 400). 16

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Table 1. Comparison of the egg sizes and endemic locations of different Paragonimus 19

species (*) 20

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Species Geographic location Egg size (Microns)

P. mexicanus Mexico, Central and South America 79 x 48

P. ecuadoriensis Ecuador 91 x 51

P. westermani Asia 100 x 56

P. kellicotti North America 42-67 x 75-118

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(*) Adapted from reference 12. 23 ACCEPTED

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