Thigh dirofilariasis diagnosed by real time sonographyc imaging: A case report Rakic-Ersek V., Miklic D., Margetic P., Salaj M., Zupetic.I, Cizmic.A, Brnic Z, Ivandic G. Klinika za traumatologiju KBC Sestre Milosrdnice Zagreb

A 70-year-old male was referred to ultrasound evaluation of a painless, subcutaneous mass in the lower third of the left thigh he had noticed two months previously On examination, the overlying and adjacent skin appeard  normal There was no pain, itching There was no palpable inguinal lymphadenopathy

Real-time sonography was performed using a high frequency transducer of 5-12 MHz

a solitary well-defined lesion in the subcutaneous soft tissues 12,6 x 5,3 x 11,7mm predominantly cystic with a thin capsule

A lesion contains numerous linear and undulating echoes with 2 parallel hyperechoic walls and an anechoic central lumen

Continuous twirling movement suggestiv of „filarial dance sign“ of live adult filarial worms.

Power Doppler – existence of blood flow only at the periphery of the nodule in capsule surrounding the worms

Possible causes of „filarial dance sign“ In Europe and some parts of Asia and Africa Dirofilariasis , mainly D.repens In tropical and subtropical regin Bancroftian filariasis - Wuchereria bancrofti Malaian filariasis – Brugia malayi Onchocercosis – Onchocerca volvulus Loaiasis – Loa loa Mansonellosis – Mansonella pastans ,

All of them may contain mature worms in subcutaneous lesions Therefore, it is also essential to obtein appropriate epidemiologic data „filarial dance sign“

All of them may contain mature worms in subcutaneous lesions Therefore, it is also essential to obtein appropriate epidemiologic data „filarial dance sign“

Current geographical distribution of canine dirofilariasis Blue - D. immitis infections Green - D. repens infections Orange - presence of both species Countries of the Mediterranean basin, Ukraine and Russia are endemic regions of dirofilariasis in Europe

Climatic changes have caused an increase in the geographical range of D.repens from the endemic sauthern to the northern regions of Europe Curent epidemiologic studies indicate that human dirofilariasis is incrising in prevalence and several authors have recently described it as an emerging zoonotic disease in diferent areas of the world

Human dirofilariasis is a zoonotic disease caused by parasites of the D. repens and D.immitis Dogs , cats and fox are the usual hosts , while human infection are sporadic and accidentally The infection is transmited by the byte of a mosquitos carrying paracitic larves In humans, the disease most often manifests as a nodular lesion in the lung ( coin-lesion), in the subcutaneous tissues or in the ocular area

Biological life cycles of D. immitis and D. repens. mf, microfilaremia. Fernando Simón et al. Clin. Microbiol. Rev. 2012;25:507-544

Once dirofilarias are infested in humans as their final host, it takes several months for them to reach sexual maturity. Famale worms can achieve length of 17cm, wheras males are smaller, about 7 cm.

The definitive diagnosis of human subcutaneous dirofilariasis can be made after surgical excision or biopsy. In order to confirm the diagnosis of D.repens infection DNA extraction followed by panfilarial polymerase chain reaction (PCR) may be performed. Surgical treatment of subcutaneous dirofilariasis in humans is considered curative. The use of antihelminthic therapy is not rutinly recommanded.

Conclusion Human subcutaneous dirofilariasis should be considered in diferential diagnosis of a subcutaneous mass. The „filarial dance sign“ seen on high-resolution sonography should strongly suggest the diagnosis of live active dirofilarial infestation. It is imperativ for radiologists in all countries to be aware of the typical imaging findings of the disease in order to arrive at the right diagnosis.

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