A case of cutaneous paragonimiasis presented with minimal pleuritis.

Clinically, paragonimiasis is broadly classified into pulmonary, pleuropulmonary, and extrapulmonary forms. The common extrapulmonary forms are cerebral and cutaneous paragonimiasis. The cutaneous paragonimiasis is usually presented as a slowly migrating and painless subcutaneous nodule. The correct diagnosis is often difficult or delayed or remained undiagnosed until the nodule becomes enlarged and painful and the cause is investigated. We report here a case of cutaneous paragonimiasis in a male child who presented with mild respiratory symptoms. The diagnosis of paragonimiasis was based on a history of consumption of crabs, positive specific serological test, and blood eosinophilia. The swelling and respiratory symptoms subsided after a prescribed course of praziquantel therapy.

INTRODUCTION

Paragonimiasis is one of the important food-borne parasitic zoonosis caused by trematode species of the genus Paragonimus which is widely distributed in the world. Paragonimus westermani has been the commonest species causing infection in humans in Asia; however, recently Paragonimus heterotremus has been increasingly detected as an important human pathogen occurring in South and Southeast Asian countries, including India.[1-3] The infection is acquired by eating raw or inadequately cooked fresh water crabs and or crayfish, which served as second intermediate host of lung fluke. Although the lungs are the primary sites of infection, Paragonimus can infect any organ or tissue of the body except bone. Extrapulmonary infection is due to the abnormal migration of the immature worms. Certain species such as P. heterotremus, Paragonimus skrjabini and P. westermani are well known to cause extrapulmonary infections in brain, skin, peritoneal cavity, and eye.[4] Cutaneous paragonimiasis can occur concurrently with pleural effusion or pulmonary infection. In some of the cases, cutaneous paragonimiasis may precede pulmonary or pleural infection. In other cases, cutaneous paragonimiasis may follow pleuropulmonary infection or it may occur without involving any other systems. The definitive diagnosis of cutaneous paragonimiasis can be made by the demonstration of Paragonimus ova and or adult worm in the excision biopsy or specific antibodies by serological test. The drug of choice for the treatment of paragonimiasis is Praziquantel, which is given in dosage of 25 mg/kg body weight in three doses per day for 3-5 days. Here we present a case of cutaneous paragonimiasis in a child because of its rarity and diagnostic confusion with other causes of benign subcutaneous swellings.

CASE REPORT

A 3.5-year-old male child from Senapati district in Manipur reported with intermittent low-grade fever, occasional non-productive cough, and mild chest pain since 6 months. There was no history of contact with known case of pulmonary tuberculosis. Physical examination revealed no abnormal findings except a diffuse subcutaneous swelling on the left posterior chest wall which was detected incidentally. The swelling was first noticed on the left upper quadrant of the abdominal wall then migrated through the right anterior chest wall to the posterior surface of left chest. The nodule measuring 4 cm in diameter was firm, non-tender and without any sign of inflammation. Chest X-ray showed no abnormal features except mild pleural reaction and thickening in both sides. Mantoux test was negative. His CBC (complete blood count) showed hemoglobin-11.8%, TLC (Total leucocyt count)-14,000/cu mm, Neutrophils-60%, Lymphocytes-28%, Monocytes-2%, Eosinophils-10% and ESR (Erythrocyte sedimentation rate)- 50 mm at the end of 1st h (Westergren's method). Stool examination for parasite ova and cyst by formol ether sedimentation technique for 3 consecutive days was negative. Aspiration cytology showed eosinophilic granulomatous exudate, leucocytes, and Charcot-Leyden crystals. Further history of dietary habit revealed that the child was non-vegetarian and had consumed smoked and fried crabs collected by the parents from the local mountain streams. On clinical suspicion serological test for paragonimiasis was advised. Dot Immunogold Filtration Assay (DIGFA) test for paragonimiasis was positive [Figure 1]. The case was finally diagnosed as cutaneous paragonimiasis with pleuritis. A course of Praziquantel at 25 mg/kg body weight three times a day for 3 days was prescribed. The swelling as well as respiratory symptoms gradually disappeared after the therapy.

Figure 1

Dot immunogold filtration assay positive test (red circle)

DISCUSSION

The primary site of paragonimiasis is the lungs; however, ectopic infection can occur with or without pulmonary infection. The factors which might contribute to aberrant migration are heavy infection, host immune status, and the adaptability of parasite species in the host. The most frequently encountered extrapulmonary forms are plural effusion followed by cerebral paragonimiasis and cutaneous infection. Clinically, cutaneous paragonimiasis is usually manifested as a non-tender migratory subcutaneous nodule, rarely the nodule may be fixed and slightly painful. Generally, the swelling appeared initially on the anterior chest or abdominal wall and then it may further migrate to the back of the chest or lower abdominal wall, pelvic region and lower limbs. Cutaneous paragonimiasis with migratory subcutaneous nodules was reported as high as 30-60% in China.[56] In India, Singh et al.,[7] have reported cutaneous infection in 7 out of 45 cases of paragonimiasis in children. Adult P. heterotremus worm was demonstrated in the excision biopsy of a subcutaneous nodule in a 10-year-old boy from Manipur.[8] All the cases of cutaneous paragonimiasis reported from Korea were associated with pleuro-pulmonary infection.[9] Subcutaneous nodule is usually single; however, multifocal nodules may occur.[10] The differential diagnosis of cutaneous paragonimiasis should include gnathostomiasis, sparganosis, and onchocerciasis, which also cause migratory subcutaneous swelling.[11] In the later cases, the migratory cutaneous nodules are usually associated with localized pain, pruritus, and erythema. In the present case, no medical attention was sought for the subcutaneous swelling as it was not causing any appreciable discomfort but to the mild respiratory infection. The respiratory symptoms might be due to the pleural reaction to the migrating worm (s) that had just entered the pleural cavity. The diagnosis of cutaneous paragonimiasis is often difficult, especially when the parasite and or ova are absent in the excision biopsy, and a specific serological test is not available. In these cases, diagnosis may be established by positive history of consumption of fresh water crabs in an endemic area, migratory nature of subcutaneous nodule and presence of numerous eosinophil and Charcot-Leyden crystals in the excised nodule and blood eosinophilia. In the present case, the diagnosis was confirmed by a positive DIGFA test. The DIGFA is a rapid, simple test as sensitive (98.8%) and specific (92%) as ELISA for detection of Paragonimus specific antibodies.[12] The kit was based on the principle of a membrane-based flow-through immunoassay technique and thus found simple and rapid. It does not require any special device and/or experienced technicians, and the results are obtained within 10 min. The test uses antigen prepared from adult P. westermani; it was found to be applicable in Japan to detect antibodies in the patient's serum infected with Paragonimus miyazakii.[13] However, if a specific serological test is available, excision biopsy may not be required for the diagnosis of cutaneous paragonimiasis. Moreover, the worm may not be present in the excision biopsy as it might have migrated to another site by the time biopsy was taken. Paragonimus ova are usually not present in the biopsy or aspirate of the nodule if the worm is immature or single. In the present case, the Paragonimus species could not be identified as worm and ova could not be detected. However, P. heterotremus would be the causative agent as it is already known to exist as causative agent of human paragonimiasis in Manipur.[2]