1. 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

2. 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

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

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

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

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

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

8. 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 ,

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

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

11. 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

12. 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

13. 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

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

15. 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.

16. 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.

17. 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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