52 Eosinophilic folliculitis and furunculosis
Sudden onset of nodules with ulceration, crusting and bleeding on the nose of a collie cross.
Canine eosinophilic furunculosis is an uncommon condition with an acute onset. It is usually confined to the nose and the muzzle, although it can occur on the pinna and the trunk. The severity of the lesions varies and many dogs will exhibit signs of pruritus. In most cases, it is thought to result from an acute hypersensitivity reaction to arthropod antigens. The condition is similar to mosquito-bite hypersensitivity in cats.
Most dogs are presented with a history of a sudden onset of symptoms. Only when questioned is the owner likely to report a possible recent exposure to insects.
In this case the owner reported that:
A physical examination revealed enlarged submandibular lymph nodes, but all other parameters were within normal limits. Multiple nodules, some with an ulcerated surface and some with a haemorrhagic crust, were present on the bridge of the nose (Fig. 52.1). The dog resented examination of this site. None of the other sites were affected in this case.
The most likely differential diagnoses based on the history were:
An adverse drug reaction can also have a sudden onset, but the dog in this case had not been medicated for over 12 months. Other less likely diagnoses include:
However, the onset in these conditions is slow and the lesions progressively worsen. Furthermore, they usually involve multiple sites, so they can easily be ruled out during the case work-up.