Hypercalcemia and Metastatic Mineralization Associated with Renal Disease in Rock Hyraxes (Procavia capensis)
The renal pathway is the primary mode of calcium excretion in the rock hyrax (Procavia capensis).1 In renal dysfunction, hypercalcemia may develop secondary to decreased calcium excretion. Two rock hyraxes at the Brookfield Zoo were clinically managed with aggressive fluid diuresis and dietary modifications for chronic azotemia and hypercalcemia, as well as hyperphosphatemia in one animal and hypophosphatemia the other. Parathyroid hormone was also elevated in one of the animals and decreased in the other compared to other hyraxes in the collection. Renal dysfunction was highly suspected as the cause for these biochemical abnormalities. In addition, both animals displayed signs of lameness due to footpad lesions. Histologically, these lesions consisted of granulomatous inflammation with mineralization reminiscent of calcinosis circumscripta. Both animals were humanely euthanized due to the severity of their lesions and progression of renal disease, and interstitial nephritis and footpad mineralization were confirmed in both animals on postmortem examination. In addition, one of the animals also exhibited multicentric metastatic mineralization affecting the kidneys, stomach, large intestine, and lung. Metastatic mineralization involving the footpads is an uncommon sequela to renal dysfunction in domestic animals,2 but has not been reported in rock hyraxes. A retrospective review of mortality data in this collection revealed a high prevalence of renal pathology, including two additional animals with metastatic mineralization and renal failure. Expanding knowledge of renal diseases will further guide preventative medicine measures, including screening for metastatic mineralization.
We thank Ms. Lauren Kane for her assistance compiling data from the medical records and the Brookfield Zoo’s keeper and veterinary technician staff for their care of these animals.
1. Leon B, Belonje PC. Calcium, phosphorus and magnesium excretion in the rock hyrax (Procavia capensis). Comp Biochem Physiol. 1979;64A:67–72.
2. Tafte AK, Hanna P, Bourque AC. Calcinosis circumscripta in the dog: a retrospective pathological study. J Vet Med. 2005;52:13–17.