Ann Thorac Surg 1999;67:201-202
© 1999 The Society of Thoracic Surgeons
Original Articles
Pulmonary dirofilariasis
Alberto Echeverri, MDa,
Robert F. Long, MDa,
William Check, MDa,
Clay M. Burnett, MDa
a Departments of Surgery, Radiology, and Pathology, Memorial Medical Center, Savannah, Georgia, USA
Accepted for publication June 10, 1998.
Address reprint requests to Dr Echeverri, Surgical Association of Gadsden, 100 Medical Center Drive, Ste 300, Gadsden, AL 35903-1145
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Abstract
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Background. Pulmonary dirofilariasis is a rare entity caused by Dirofilaria immitis, the dog heartworm that is transmitted to humans by mosquitos. This filarial nematode enters the subcutaneous tissue, travels to the right ventricle where it dies, and then embolizes the pulmonary vasculature, causing a small pulmonary infarction, which subsequently appears as a solitary nodule. Although these nodules are usually identified incidentally by chest radiography in asymptomatic patients, the lesion is generally presumed to be neoplastic. Diagnosis is made by surgical excision.
Methods. We reviewed the pathology reports at Memorial Medical Center, Savannah, GA since 1990.
Results. There have been approximately 150 cases reported in the literature worldwide. We found 4 patients with pulmonary dirofilariasis diagnosed at our hospital since 1992. A review of the pathogenesis of the disease and clinical manifestations, diagnosis, and treatment of this entity are presented.
Conclusions. Pulmonary dirofilariasis is a benign condition, transmitted by mosquitos to humans that results in peripheral pulmonary nodules. Awareness of this entity is important in the differential diagnosis of pulmonary coin lesions.
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Introduction
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Pulmonary dirofilariasis is a rare, zoonotic disease, caused by Dirofilaria immitis (dog heartworm) that is usually transmitted from dogs to humans by mosquitoes [1]. Approximately 150 cases have been reported in the literature worldwide [2]. Dirofilaria ("evil thread") [3] is a parasite of carnivores, with a tropical and subtropical distribution in Southern Europe, Asia, Australia, and North and South America [1, 4, 5].
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Case reports
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Patient 1
In March 1992, a 74-year-old white woman was evaluated for lumbar laminectomy and found to have a new pulmonary nodule in the right upper lobe. Computed tomography of the chest demonstrated a noncalcified, well-defined 2.0-cm mass in the posterior segment of the right upper lobe associated with pleural reaction. Bronchoscopy was negative. Percutaneous transthoracic fine-needle aspiration biopsy showed necrotic lung parenchyma, but necrotic tumor could not be excluded. The patient underwent right posterolateral thoracotomy and wedge resection of the lesion in the right upper lobe. Pathologic analysis confirmed a pulmonary infarction caused by D immitis.
Patient 2
In October 1995, a 37-year-old black man with history of schizophrenia was found to have an incidental noncalcified 1.0-cm peripheral nodule in the right upper lobe. The patient underwent thoracoscopic wedge resection of the nodule. Pathologic analysis demonstrated a 0.8-cm tan-gray nodule with necrosis and degenerating fragments of D immitis.
Patient 3
In May 1996, a 78-year-old white woman was admitted for chest pain and had an incidental 2.0-cm left lower lobe nodule discovered on chest radiography. Computed tomography of the chest confirmed a solid lesion and identified another smaller lesion in the same lobe (Fig 1). At thoracotomy, a total of three nodules in the left lower lobe were found. Pathologic analysis demonstrated a 1.6 x 1.2 x 1.0-cm soft tan granuloma containing D immitis. The other lesions were 0.5-cm benign silicotic nodules.
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Fig 1. (Patient 3.) Computed tomographic scan showing a noncalcified, well-circumscribed pulmonary nodule in the left lower lobe.
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Patient 4
In September 1996, a 62-year-old asymptomatic white man was found to have a 1.0-cm right lower lobe pulmonary nodule on routine chest radiography. Computed tomography confirmed a noncalcified right lower lobe nodule. The patient underwent uncomplicated thoracoscopy and wedge resection. Pathologic analysis demonstrated granuloma with D immitis.
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Comment
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Dirofilaria immitis, a filarial nematode, is an unusual cause of solitary pulmonary nodules. Magalhaes first reported a human infection from Dirofilaria in 1887, in the left ventricle of a male child in Brazil as reported in Panayiotis and colleagues [5]. Dashiell [6] reported a case with pulmonary infarction in 1961. The majority of patients reside in the southeastern United States. Other countries that have reported cases are Japan, Australia, Italy, Costa Rica, and the Netherlands. Hosts, other than the dog, include the cat, fox, muskrat, wolf, otter, coyote, sea lion, and jackal [1, 4].
Life cycle
Mature Dirofilaria infection in the dog results in a coiled and parasitic mass in the right ventricle, with the microfilaria circulating in the bloodstream. The microfilaria are transmitted to humans by mosquitos from the genera Anopheles, Aedes, Culex, and Myzorhynchus [3]. The infected mosquito injects the larvae into the host animal, where they mature in the subcutaneous tissue. The human is an accidental terminal host. When the Dirofilaria is able to survive in the human subcutaneous tissue, it migrates to the right ventricle, where it develops into a sexually immature worm. The worm dies and embolizes the pulmonary artery, causing a pulmonary infarction [5, 7].
Clinical features
Most human infections have been in adults. The patients are generally asymptomatic, and a single pulmonary nodule from 1 to 3 cm is identified in the periphery of the lung on routine chest radiography. Clinical symptoms may include cough, chest pain, hemoptysis, fever, chills, and malaise [8].
Pathologic analysis
Macroscopically, the dirofilarial nodule is well-circumscribed, grayish yellow, and ranges from 1 to 3 cm in diameter. Microscopically, there is a well-formed, well-circumscribed granuloma that usually contains easily identifiable fragments of the parasite (Fig 2) firmly lodged in the affected pulmonary artery. There is a central area of coagulative necrosis surrounded by a wall of fibrous tissue containing epithelioid cells, Langhans’ giant cells, lymphocytes, plasma cells, and fibroblasts.
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Fig 2. Cross section of pulmonary granuloma with fragments of parasite. (Hematoxylin and eosin stain, x100 before 50% reduction.)
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Diagnosis
Dirofilariasis should be included in the differential diagnosis in patients with asymptomatic, small, solitary pulmonary nodules. Serologic tests, transthoracic fine-needle biopsy, bronchial washing, biopsy, and sputum cytologic analysis lack specificity for accurate diagnosis [8, 9]. Diagnosis by fine-needle aspiration biopsy is rare, although parasite fragments have been identified in two reported cases [5], obviating the need for excisional biopsy.
Treatment
Simple surgical excision is recommended unless dirofilarial fragments are found by needle aspiration.
Conclusion
Human pulmonary dirofilariasis is a benign condition, transmitted by mosquitos to humans as an accidental host, that results in small, solitary peripheral pulmonary nodules. Awareness of this entity is important in the differential diagnosis of pulmonary coin lesions.
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References
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Neafie R.C., Connor D.H., Meyers W.M. Dirofilariasis. In: Binford C.H., Connor D.H., eds. Pathology of tropical and extraordinary diseases. Washington, DC: Armed Forces Institute of Pathology, 1976:391-396.
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Cordero M., Munoz R., Muro A., Simon F., Perera L. Small calcified nodule: an undescribed radiologic manifestation of human pulmonary dirofilariasis. J Infect Dis 1992;165:398-399.[Medline]
-
Jarratt M. Solitary pulmonary nodule in a 62-year-old man. Chest 1995;107:271-273.[Free Full Text]
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Ciferri F. Human pulmonary dirofilariasis in the West. West J Med 1981;134(2):158-162.[Medline]
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Panayiotis J.A., Katras A., Christie B. Pulmonary dirofilariasis, the largest single-hospital experience. Chest 1992;102:851-855.[Abstract/Free Full Text]
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Dashiell G.F. A case of dirofilariasis involving the lung. Am J Trop Med Hyg 1961;10:37-38.[Medline]
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Adkins R.B., Dao A.N. Pulmonary dirofilariasis: a diagnostic challenge. South Med J 1984;77:372-374.[Medline]
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Roy B.T., Chirurgi V.A., Theis J.H. Pulmonary dirofilariasis in California. West J Med 1993;158(1):74-76.[Medline]
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Glickman L.T., Griere R.B., Schawtz P.M. Serologic diagnosis of zoonotic pulmonary dirofilariasis. Am J Med 1986;80:161-164.[Medline]
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Abstract
Introduction
