Extensive epidermal naevus in a foal.

This research article discusses a case study of a 2-month-old Standardbred filly horse, that had extensive congenital skin lesions. The lesions were surgically removed, and there were no signs of recurrence after 6 weeks. The study challenges early reports that attribute papillomas to in-utero infection with papillomavirus despite a lack of supporting histological evidence. Thus, a change in nomenclature from congenital papilloma to epidermal naevus is proposed for this condition in horses.

Case Overview

• This research examines the case of a 2-month-old Standardbred filly which had been presented for examination and treatment.
• The foal had extensive skin lesions or growth abnormalities, also known as naevi or hamartomas, with a linear distribution on its left leg.
• These lesions were surgically excised under general anesthesia, and there were no signs of recurrence 6 weeks post surgery.

Comparison to Previous Cases and In-utero Infection Hypothesis

• This filly had a greater number and distribution of lesions when compared to prior reported cases of congenital papilloma in foals.
• Early reports on congenital papillomas in horses have suggested in-utero infection with papillomavirus as the cause.
• However, in this case study no histological features associated with papillomavirus infections were found. Further, papillomavirus immunohistochemistry has also returned negative in previously tested cases.

Nomenclature and Conclusion

• The researchers in this study propose a change in name for this condition in horses, from congenital papilloma to epidermal naevus.
• They draw similarity to a condition in humans known as verrucous epidermal naevus, due to the presence at birth, the appearance and the extensive distribution of lesions.
• This name change better reflects the nature of these lesions as skin growth abnormalities, as opposed to attributing them to papillomavirus infection.