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Pulmonary dirofilariasis--clinicopathological study
Hiroshi Hirano1, Tomohiko Kizaki, Terumasa Sashikata
1Department of Pathology, Toneyama National Hospital, Osaka, Japan.
Abstract:
Pulmonary dirofilariasis (PD), caused by Dirofilaria immitis (D. immitis), the dog heartworm, is not common in humans, though we recently encountered 4 cases. Chest X-ray images from annual health examinations showed a single spherical nodule in the inferior or middle portion of the right lung in each patient. None of the patients showed any clinical symptoms and had no contact with dogs. Hematological results in 3 of the cases were within normal limits, while mild eosinophilia was found in one. Serological tests for the Anti-Dirofilaria antibodies were not performed. There were no characteristic clinical manifestation of PD in any of the patients, however, we consider it important to keep a diagnosis of PD in mind, when we experienced these cases, they present no characteristic clinical manifestations. Pathologically, macroscopic findings showed well-circumscribed nodules that were round peripheral lesions in lungs. Histological results revealed coagulation necrosis with fibrosis and granulation in the nodule edge, which contained inflammatory cells. By means of silver staining, the worm structures in the nodules could be identified well, and the quadrant cells in the sections were numbered about 30. Immunohistochemically, the somatic muscle tissues were stained with anti-Dirofilaria antibody. These findings indicated that the pulmonary lesions in all 4 cases were due to D. immitis.
Insights
Pulmonary dirofilariasis, a rare lung infection caused by the dog heartworm Dirofilaria immitis, can present as asymptomatic nodules. Diagnosis requires careful pathological examination due to the lack of distinct clinical signs.
Area of Science:
- Veterinary parasitology
- Human infectious diseases
- Pulmonary pathology
Background:
- Pulmonary dirofilariasis (PD) is an uncommon parasitic infection in humans, typically caused by Dirofilaria immitis, the canine heartworm.
- Human cases are often asymptomatic and diagnosed incidentally through imaging studies.
- Understanding the presentation and diagnosis of PD is crucial for public health.
Observation:
- Four human cases of pulmonary dirofilariasis were recently identified.
- Patients presented with single, spherical nodules in the right lung on chest X-rays.
- No clinical symptoms or direct contact with dogs were reported; mild eosinophilia was noted in one case.
Findings:
- Pathological examination revealed well-circumscribed, round nodules in the lungs.
- Histology showed coagulation necrosis, fibrosis, and inflammation at the nodule edges.
- Silver staining and immunohistochemistry confirmed the presence of Dirofilaria immitis structures within the nodules.
Implications:
- Pulmonary dirofilariasis should be considered in the differential diagnosis of pulmonary nodules, even in the absence of typical risk factors.
- Accurate diagnosis relies on integrating imaging, pathological, and specific serological or immunohistochemical findings.
- Further research into human dirofilariasis is warranted to better understand its epidemiology and clinical spectrum.
