Hypophosphatasia (HPP)

Hypophosphatasia (HPP) is a metabolic bone disease characterized by defective skeletal mineralization which has been described in the breed Karelian Bear Dog as well as in humans. For the Karelian Bear Dog, a variant in the alkaline phosphatase gene ALPL has been found to be associated with HPP. The age of onset of HPP in Karelian Bear Dogs varies between 2 to 10 weeks. First symptoms are growth retardation, crouched stance, seizures, generalized muscle weakness and movement difficulties. Due to the variant in the ALPL gene, a defective skeletal mineralization together with skeletal ossifications could be observed. Typical pathological findings are hyperextension of the distal joints, hourglass-shaped diaphysis as well as poorly mineralized epiphyses, carpal and tarsal bones. Moreover, the serum analysis of affected puppies revealed elevated total serum protein, albumin and urea levels and an increased level of excreted PEA (phosphatase substrate phosphoethanolamine) could be measured in the urine. The puppies usually die a few weeks after the first symptoms or are euthanized due to severity of the clinical signs.