Ringtail in suckling Munich Wistar Fromter rats: A histopathologic study

Ringtail is a pathologic condition of the tail of rats and other rodents th at is traditionally attributed to low environmental humidity, although diet ary deficiencies, genetic susceptibility, environmental temperature, and de gree of hydration of the animal also have been suggested as possible causes . To the authors' knowledge, a detailed histopathologic study that may serv e to shed light on the etiopathogenesis of this disease has not yet been pu blished. We describe the histologic findings of ringtail observed in 12 suc kling Munich Wistar Fromter (MWF) rats from two litters. Epidermal hyperpla sia characterized by orthokeratotic and parakeratotic hyperkeratosis and ac anthosis was observed in all affected rats. Numerous often dilated vessels were present in the dermis of tails that appeared of red/brown color at gro ss examination. In severe cases, the dilated vascular structures were throm botic and accompanied by dermal hemorrhages and focal coagulative necrosis of the overlying epidermis, These findings suggest that epidermal acanthosi s and hyperkeratosis are the main and primary events in the development of ringtail. To clarify the cause of this disease, future studies should be fo cused on the numerous factors that can induce such epidermal changes.