CMYKP

Adynamic bone disease; chronic kidney disease; mineral bone disease. DEFINITION AND CLASSIFICATION OF CKD-MBD Chronic kidney disease (CKD) leads to distur-bances of bone and mineral metabolism. The former term, renal osteodystrophy (ROD), has been inte-grated into the term “chronic kidney disease-mineral and bone disorder ” (CKD-MBD) thus indicating the close relationship between mineral disorder and bone and renal disease1. Renal osteodystrophy con-sists of several subtypes with important differences in aetiology and fundamental differences in treat-ment strategies. Long-term dialysis patients exhibit a nearly 100 % prevalence of some type of ROD, which illustrates the importance of this sort of comorbidity2. The TMV nomenclature, explained in the recent KDIGO guidelines, discriminates between several variants of MBD1. In this system T classifies bone turnover, M bone mineralisation and V bone volume. Bone turnover and bone volume may both be ranked as high, normal or low. Bone mineralisation may be categorised as normal or abnormal. Alterna-tive to volume, the bone balance may be consid-ered3,4. According to this classification, six types of bone pathology in CKD-MBD can be distinguished (Table I). Despite concerns about the importance of histomorphometric parameters, a CKD-MBD classi-fication is helpful in clinical practice and widely used as the basis for therapeutic approaches. DEFINITION OF ABD The term “adynamic ” bone disease, introduced in the early 1980s5,6, describes a low-bone turnover with a reduced number and/or activity of osteoblasts and without osteoid accumulation. Low levels of osteoid differentiate ABD from the other low-turnover ROD, i.e. osteomalacia. The “original ” ABD is char-acterised by reduced collagen synthesis, whereas osteomalacia, a defect in bone mineralisation, leads to impaired bone formation7,8. Peritrabecular fibro-sis, or marrow fibrosis, is minimal or absent (in contrast to osteitis fibrosa). As a consequence, the bone formation rate is substantially diminished and the number of remodelling sites is low7