Bone histomorphometry in adult patients with cystic fibrosis

Study objective: Low bone mineral density is a common complication of cysti c fibrosis (CF), and recent studies have implicated vitamin D insufficiency as a significant etiologic factor. The aim of this study was to establish whether there was bone biopsy evidence of vitamin D deficiency osteomalacia in patients with CF and to document the general histomorphometric characte ristics of CF bone. Patients and methods: A retrospective descriptive and histomorphometric stu dy of postmortem L2/L3 vertebral bone biopsy specimens was undertaken on ti ssue from 11 posttransplant CF patients and 4 nontransplanted CF patients. Control data were derived from postmortem bone specimens from 15 young adul ts. Results: Bone from all CF patients was characterized by severe osteopenia i n both trabecular and cortical bone. At the cellular level, there was decre ased osteoblastic and increased osteoclastic activity, The reduction in ost eoblastic activity was due to both a decrease in osteoblast number and a de crease in the biosynthetic potential of osteoblasts, The osteoclastic chang es were due to an increase in the number of osteoclasts, The increase in os teoclasis and the uncoupling of osteoblastic and osteoclastic activity resu lted in an increase in resorptive surfaces. Although there were few signifi cant differences between the transplanted and nontransplanted CF groups, bo th cortical and trabecular bone mass tended to be lower after transplantati on. None of the CF undecalcified biopsy specimens showed osteoid parameters characteristic of vitamin D deficiency osteomalacia, Conclusions: CF patients have an unusual and complex pattern of cellular ch anges within bone that are not typical of vitamin D deficiency osteomalacia .