Les ichtyoses du chien

Abstract

Ichthyosis includes a group of hereditary disorders affecting the process of corneogenesis, characterised by scaling of the skin with or without epidermal proliferation or dermal inflammation. In dogs, ichthyosis varies in its clinical presentation (particularly the type of scaling), medical and zootechnical seriousness based on the breed, and therapeutic response. Also, certain types of canine ichthyosis may provide good spontaneous models to study ichthyosis in man. Epidermolytic ichthyosis is due to a lack of epidermal keratins (K10). Non-epidermolytic ichthyosis described in dogs is similar to lamellar ichthyosis in man, caused by a lack of activity of transglutaminases 1. Non-epidermolytic ichthyosis is associated with a dull coat and whitish or greyish scaling affecting the whole body. In hairless areas, the skin is rough, described as “ sandpaper skin”, and may become gradually pigmented. Digital pads and nose may be affected as well. Sometimes, hair anomalies (woolly, short, fine, or frizzy) are seen. General symptoms (growth retardation, bilateral keratoconjunctivitis sicca) are observed in certain Cavalier King Charles at a very young age (as early as 2 to 3 months). Epidermolytic ichthyosis is associated with scales in a striated pattern, often pigmented, with moderate exfoliation, and sandpaper skin. Digital pad involvement has not been described. Diagnosis is based on anamnesis (age of onset, breed), symptoms, and skin biopsies. Histopathology of the lesions is used to distinguish epidermolytic from non-epidermolytic forms. Ultrastructural studies of the biopsies may help define the type of ichthyosis. The prognosis depends on the type of ichthyosis and the breed. The objective of the treatment, which is exclusively symptomatic, is to correct the excessive production of scales and improve skin hydration with keratolytic shampoos containing sulphur, salicylic acid, and emollients.