A 79-year-old man was admitted with a compression fracture of the first lumbar vertebra. His alkaline phosphatase (ALP) level was 35 IU/L, and his dual energy X-ray absorptiometry T score was -3.7 standard deviations, indicating osteoporosis. A genetic analysis showed a mutation of the alkaline phosphatase biomineralization-associated gene encoding tissue-nonspecific alkaline phosphatase. Hypophosphatasia-related osteoporosis was diagnosed. Alendronate, teriparatide, and minodronate were administered in that order. The ALP level increased during teriparatide use. A bone biopsy performed after three years of teriparatide treatment showed that cancellous bone was adynamic. In cortical bone, tetracycline double-labeling indicates enhanced bone formation. Teriparatide may thus be a viable treatment option even in patients with hypophosphatasia.
Keywords: bone histomorphometric analysis; hypophosphatasia; teriparatide.