[Benign familial hyperphosphatasemia. A report of one case and diagnostic considerations]

Benign familial hyperphosphatasemia is a rare biochemical abnormality characterized by the presence of persistently elevated levels of serum alkaline phosphatase in several members of the same familiy, in the absence of disease or any known cause of hyperphosphatasemia. We describe one family affected with this biochemical abnormality and the epidemiology, genetic, isoenzymatic patterns and clinical significance of this entity are discussed.A 61-year-old man was referred to the Unit of Metabolic Bone Diseases for investigation of a lumbar pain with a history of urolithiasis and inguinofemoral hernia repair. The results of the physical examination and laboratory analysis were normal except for a high serum alkaline phosphatase level of 690 UI/l (reference range 40-129 UI/l). Isoenzymatic profile showed a 50% of intestinal variant, 33% of bone variant and 17% of liver variant isoenzymes. Skeletal radiographs and lumbar magnetic resonance imaging showed signs of osteoarthritis in the spine, bone scan showed a skeletal distribution of the radioisotope.One year later the biochemical exams showed similar raised levels of alkaline phosphatase. Family investigation revealed that one of the three sons of the patient had the same biochemical disorder.