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