Three rock hyraxes (Procavia capensis) maintained in a zoological collection had chronic hypercalcemia and azotemia. In addition, all animals displayed signs of lameness due to footpad lesions that were histologically characterized as marked metastatic mineralization with granulomatous inflammation, reminiscent of calcinosis circumscripta. Although the animals were managed with aggressive fluid therapy, calciuresis, and dietary modification, all were eventually humanely euthanized due to the severity of their footpad lesions and/or progression of renal disease. Metastatic mineralization was also noted in other soft tissues among the three cases, including the stomach, colon, lung, vascular wall, ovary, and kidney. Varying degrees of interstitial nephritis were confirmed on postmortem examination, and in the absence of other causes for hypercalcemia, metastatic mineralization was presumably the consequence renal dysfunction. The renal pathway is the primary mode of calcium excretion in the rock hyrax. In renal dysfunction, hypercalcemia may develop secondary to decreased calcium excretion. Footpad mineralization is an uncommon sequel to renal dysfunction in domestic animals but has not been reported in rock hyraxes. A retrospective review of mortality data in this collection revealed a notable prevalence of renal lesions, including two additional animals with metastatic mineralization and renal dysfunction. Expanding knowledge of renal diseases will further guide preventative and clinical measures, including screening for metastatic mineralization and therapeutic trials for management of hypercalcemia and calcium mineral deposition in the footpads and other soft tissues.
Keywords: Footpad; Procavia capensis; hypercalcemia; kidney; mineralization; rock hyrax.