Endogenous calcitriol production and ionized hypercalcemia in 7 dogs with chronic dermatopathy of infectious and noninfectious etiology (2016-2024).

Abstract

BACKGROUND: Hypercalcemia associated with granulomatous disease in dogs can present a diagnostic challenge. HYPOTHESIS/OBJECTIVES: Excessive endogenous, extrarenal calcitriol production is a potential mechanism of ionized hypercalcemia in dogs with granulomatous skin conditions. ANIMALS: Hypercalcemic client-owned dogs (n = 7) with chronic skin disease seen in general and specialty practices with calcium profiles submitted to a university veterinary diagnostic laboratory by the attending clinician. METHODS: Descriptive case series reporting clinical presentation, laboratory findings, treatment, and outcome of 7 hypercalcemic dogs with dermatopathies of varying etiology. RESULTS: Panniculitis was confirmed histologically in 5 dogs (idiopathic, n = 4; presumed bacterial, n = 1). The other 2 dogs had severe generalized demodicosis (n = 1) and demodectic/sarcoptic mange with superficial and deep pyoderma (n = 1). Initial testing showed clinically relevant parathyroid-independent ionized hypercalcemia, undetectable parathyroid hormone-related protein concentration, and 25-hydroxyvitamin D concentration close to or below the lower reference limit in all dogs. Calcitriol concentration was above reference interval in 6 dogs at initial testing, and near the upper reference limit in 1 dog 29 days after presentation. In all cases, normalization of calcium and vitamin D homeostasis paralleled clinical improvement with appropriate therapy for the underlying skin condition. CONCLUSIONS AND CLINICAL IMPORTANCE: Ionized hypercalcemia apparently mediated by excessive extrarenal calcitriol production can be seen in dogs with granulomatous skin disease. Calcitriol measurement should be included with other calcium-related testing in the workup of unexplained hypercalcemia with concurrent chronic skin disease.