Pulmonary dirofilariasis: a diagnostic challenge

Area of Science:

• Veterinary Pathology
• Human Pathology
• Parasitology

Background:

• Dirofilaria immitis, the canine heartworm, is a known cause of pulmonary granulomas in humans.
• Reported cases in the United States are rare, primarily concentrated along coastal regions.
• No cases have been previously documented in the Mississippi Valley states.

Observation:

• A patient with a history of smoking presented with an enlarging pulmonary nodule.
• Diagnostic imaging revealed a suspicious lesion requiring surgical resection.
• The resected nodule was found to contain a filarial worm.

Findings:

• Histopathological examination confirmed the presence of Dirofilaria immitis within the pulmonary nodule.
• The case represents a rare instance of human dirofilariasis in the Mississippi Valley.
• The parasitic granuloma mimicked a neoplastic lesion on initial evaluation.

Implications:

• This case underscores the importance of considering parasitic infections in the differential diagnosis of pulmonary nodules.
• It highlights the diagnostic challenges in distinguishing parasitic lung lesions from lung neoplasms, especially in atypical geographic locations.
• Further awareness and diagnostic vigilance are necessary for identifying human dirofilariasis, even outside endemic areas.