Characterization and management of a Jack Russell terrier with congenital ichthyosis

A prospective clinical trial was carried out in a 6-week-old male Jack Russell terrier with congenital ichthyosis to evaluate stratum corneum lipids; transmission electron microscopy of skin specimens; and clinical and dermatopathological response to vitamin A alcohol therapy. Also evaluated were the clinical, dermatopathological, and epidermal cell proliferation kinetics response to a synthetic retinoid in a dog with congenital ichthyosis.  Epidermal cell renewal time was markedly decreased compared with normal and seborrhoeic dogs. Skin specimens were characterized by severe and diffuse compact orthokeratosis that extended into the infundi-bulum of the hair follicles. The stratum granulosum was normal. On transmission electron microscopy, the stratum corneum was thickened and intercorneocyte spaces were extremely narrow. The first three corneocyte layers contained tonofilaments that were irregular, coarse and wavy. Tonofilament packing appeared more normal and regular in the fourth and fifth corneocyte layers. Outer layers of stratum corneum were extraordinarily electron-dense compared with normal. There was a decrease in stratum corneum free fatty acid and acyl-ceramide and an increase in ceramide III levels compared with three normal dogs. Three months of oral vitamin A alcohol did not result in clinical improvement, although histologically the orthokeratosis was less compact. After 6 months of oral etretinate therapy, comedones and scales were markedly less evident grossly. Although compact orthokeratosis was still present on histological examination of skin, it was less than that present at 6 weeks of age. Epidermal cell kinetics were not altered after etretinate therapy.