Linear organoid nevus in a dog

A skin lesion classified as linear organoid nevus is reported in a female standard Schnauzer. The dog was brought to the clinic with multiple hyperpigmented, hyperkeratotic linear or ovoid plaques on the head, neck, trunk, ears, and limbs. Histological findings included severe orthokeratotic hyperkeratosis, focal parakeratosis and hyperplasia of both the epidermis and the follicular infundibular epithelium, and marked sebaceous hyperplasia. No improvement was noted with systemic retinoid therapy. This is the second linear organoid nevus described in a dog, and the first report of retinoid therapy for this disease.