Detection of Dirofilaria (Nochtiella) repens DNA by polymerase chain reaction in embedded paraffin tissues from two human pulmonary locations. Case report

We here report two new cases of human pulmonary dirofilariasis in men aged 62 and 64 from Northern and Central Italy, respectively. Both were asymptomatic and the infections were discovered incidentally when chest radiographs taken for another reason revealed the presence of a coin lesion. The initial clinical diagnosis was oriented towards a lung tumour, and an excisional lung biopsy after thoracotomy was necessary for the final diagnosis. Pathologically, the lesion consisted of a roundish subpleural infarct with a central thrombotic artery containing sections of an immature nematode: Dirofilaria repens was diagnosed histologically in one case, the necrotic condition of the worm allowing only genus identification, Dirofilaria, in the other case. In both samples, PCR analysis amplified a 246 bp product, specific for the IpS insert 11 of D. repens. The authors stress the role of PCR in the diagnosis of this parasite from paraffin samples, also in cases in which identification of the species was not possible by conventional morphology due to poor conservation of the worm. These cases represent the first PCR-based diagnosis of D. repens in a human pulmonary dirofilariasis on samples embedded in paraffin.