Treatment of osteoporotic fractures in alkaptonuria by teriparatide stimulates bone formation and decreases fracture rate – A report of two cases

Two cases of advanced alkaptonuria (AKU) with co-existing osteoporosis are described. Case 1 developed multiple non-vertebral fragility fractures, while Case 2 developed vertebral fragility fractures, both refractory to bisphosphonates. Difficulties in diagnosing osteoporosis in AKU complicated by extensive calcifying and ossifying spondylosis are discussed. Both patients continued to fracture despite nitisinone therapy for metabolic control of AKU, as well as bisphosphonate antiresorptive therapy for osteoporosis. Subsequently the patients were treated with teriparatide 20 μg subcutaneous injections daily for two years, leading to reduction in fractures soon after commencing therapy in both cases. Markers of bone remodelling P1NP and CTX were stimulated. No complications due hypercalcaemia or calcification were encountered in either case. We conclude that teriparatide is an effective adjunct in the treatment of AKU when bisphosphonates prove ineffective.