Figure 1. Dog with iatrogenic calcinosis cutis. Note the thick plaques on the dorsal neck and trunk. Calcinosis cutis starts with a papular eruption that can progress to thick plaques of calcification and mineralization.
In dogs, endocrine disease can manifest with a variety of cutaneous signs. In some cases, signs may not be disease specific; for example, both Cushing’s disease and hypothyroidism can trigger demodicosis, secondary skin infections (bacteria and yeast), and truncal alopecia with comedones (blackheads). In comparison, certain signs can be identified with a disease process, such as rat tail in dogs with hypothyroidism; in these patients, alopecia is primary and not secondary to pruritus, as is observed in dogs with flea allergy.
Figure 2. Yorkshire terrier with alopecia X. Note the truncal hyperpigmentation and alopecia. This disease typically spares the head and extremities.