Evaluation of Bone Architecture and Bone Strength in Adults With Hypophosphatasia (HPP)

Inclusion criteria HPP-Group: * Genetically verified HPP * Age: ≥ 18 years * Persistently low levels of alkaline phosphatase (ALP) ≤ 35 U/L (normal range 35-105 U/L) * At least one of the following symptoms: a) dental manifestations; b) musculoskeletal pain; c) history of fracture(s) * Submitted informed consent Inclusion Criteria Control-Group: * No ALP measurements ≤ 45 U/l and ≥ 50% of all ALP measurements, registered in the electronical clinical journal ≥ 55 U/l * Normal parathyroid hormone (PTH) and Pyridoxal-5´-phosphate (PLP) * Vitamin D3 ≥ 25 nmol/L * Submitted informed consent Exclusion criteria HPP-Group: * Pregnancy * Skin infection or severe skin affection in the measurement area of microindentation * Known allergy to Lidocain * Former or current medical treatment influencing bone metabolism (oral corticosteroid \> 12 weeks, former or current anti-osteoporosis treatment at any time (regardless drug holiday), all kind of sex steroids (excluding oral contraception), anti-convulsants) * Current malignant disorders Exclusion Criteria Control-Group: * Family history of a genetic metabolic bone disease (HPP, Osteogenesis imperfecta) * Rickets in childhood * Former or current Osteoporosis * Former or current Osteomalacia * Known diabetes * Former or current medical treatment influencing bone metabolism (oral corticosteroid \> 12 weeks, former or current anti-osteoporosis treatment at any time (regardless drug holiday), all kind of sex steroids (excluding oral contraception), anti- convulsants) * Skin infection or severe skin affection in the measurement area of microindentation * Chronic liver or gallbladder disease * Current malignant disorders * Former or current thyrotoxicosis (T4 over normal range ≥ 6 months) * Cushing disease * Pregnancy