Benign familial hyperphosphatasemia in Siberian Huskies

OBJECTIVE: To evaluate benign familial hyperphosphatasemia involving serum alkaline phosphatase (SAP) in pups. DESIGN: Pups with markedly increased SAP activity were evaluated and compared with unaffected siblings, and with other unaffected Siberian Husky pups from the same colony. ANIMALS: 8 related litters of Siberian Husky pups (n = 56). PROCEDURE: At ages 11 and 16 weeks, pups were given physical examinations and blood was obtained for hematologic and serum biochemical analyses (including electrolytes and isoenzymes of alkaline phosphatase), ionized calcium concentration, and serum parathyroid hormone concentration. Diet, growth and health performance, skeletal radiographs, and genealogical data also were evaluated. RESULTS: Of 42 pups tested, 17 had markedly high total SAP values. Mean total SAP activity of affected pups at ages 11 and 16 weeks was over 5 times greater than mean total SAP activity of unaffected siblings and other unaffected Siberian Husky pups of the same age (P < 0.001). Clinical, radiologic, and biochemical evaluation of the subjects revealed no other abnormal findings. The source of the increased SAP activity was characterized in 5 affected pups as bone isoenzyme. The mode of inheritance could be deduced from the data, but the trait clearly is familial and autosomal. CONCLUSION: The condition described in the family of Siberian Huskies bears similarity to human benign, persistent, familial hyperphosphatasemia. CLINICAL RELEVANCE: Benign familial hyperphosphatasemia should be considered in the differential diagnosis of markedly increased SAP activity in young dogs.