Osteomalacia, which means “soft bones,” results from impaired mineralization of bone matrix as a result of inadequate concentrations of serum phosphate and/or calcium or from a circulating inhibitor of mineralization.
Osteomalacia/rickets causes pain and deformity in the long bones and pelvis. Laboratory features of those with osteomalacia resulting from vitamin D deficiency include:
low or low/normal serum calcium and phosphate levels, low 25-OH vitamin D levels, elevated serum alkaline phosphatase, elevated PTH levels, and low 24-hour urinary calcium excretion.
Laboratory features of those with osteomalacia caused by renal phosphate wasting (familial hypophosphatemic rickets/adult-onset vitamin D-resistant osteomalacia and oncogenic osteomalacia) include low serum phosphate, high serum alkaline phosphatase, high urinary phosphate (low tubular reabsorption of phosphate), and inappropriately normal or low 1,25 (OH)2 vitamin D for the degree of hypophosphatemia. In adults, radiographs may show characteristic pseudofractures (milkman’s fractures, Looser’s zones) where large arteries cross bones; in children, radiographs may show changes consistent with, rickets
Bone biopsies show increased osteoid seams but with reduced hydroxyapatite deposition.