Author: Karina Fresneda DVM DiplACVP

Canine facial eosinophilic folliculitis and furunculosis is an acute, generally self-limiting inflammatory condition. Although its exact pathogenesis is not known, the good response to corticosteroids suggests a hypersensitivity mediated pathogenesis, where insect stings or spider bites are suspected to be triggering factors.

It starts as pruritic, papular, pustular and ulcerative lesions on the bridge of the nose and muzzle and may spread to other areas of the head and, sometimes, trunk and limbs. Pruritus may be severe, although some cases are not pruritic but rather painful.

The main histological findings are eosinophilic perifolliculitis, folliculitis and furunculosis. Marked dermal and subcutaneous mucinosis and ulceration are common. In our case the histological findings were moderate irregular epidermal hyperplasia with moderate spongiosis and a large focally extensive ulcer. Overlying the ulcer there was a serocellular crust. In superficial and deep dermis, often surrounding dermal adnexa and infiltrating and effacing multiple hair follicles, there was an inflammatory infiltrate composed of numerous eosinophils and fewer neutrophils, histiocytes, lymphocytes and plasma cells.

The differentials could include staphylococcal nasal folliculitis and furunculosis, dermatophytosis, solar dermatosis, juvenile cellulitis and autoimmune skin diseases. The prognosis is good. Without glucocorticoid treatment, spontaneous recovery usually occurs within 3 weeks, but systemic prednisone hastens resolution of the lesions. Any secondary pyoderma should be treated with appropriate systemic antibiotics.

Eosinophilic dermatitis, folliculitis and furunculosis

Eosinophilic dermatitis, folliculitis and furunculosis

Significant intraluminal follicular inflammation composed mainly of eosinophils

Eosinophilic dermatitis and furunculosis

References

Muller & Kirk’s Small animal dermatology. Miller WH, Griffin CE and Campbell KL. 7th edition.2013 Elsevier.  Pages 416-417.

Small animal dermatology. A color atlas and therapeutic guide. Hnilica KA, Patterson AP. 4th edition. 2017. Elsevier. Page 241

Canine eosinophilic folliculitis and furunculosis in three cases. C. F. Curtis, R. Bond, A. S. Blunden, D. G. Thomson, P. E. McNeil, T. W. Whitbread. Journal of small animal practice. Volume36, Issue3. March 1995. Pages 119-123.

Eosinophilic Folliculitis in a Dog. Gabriel Utida Eguchi, Alda Izabel de Souza, Veronica Jorge Babo-Terra, Luiz Henrique de Araújo Machado and Mariana Isa Poci Palumbo. Acta Scientiae Veterinariae, 2021. 49(Suppl 1): 694. CASE REPORT. October 2021.