Abnormal vitamin D metabolism | (causing secondary hyperparathyroidism and hypophosphatemia) | Deficient intake or absorption | Dietary | Inadequate sunlight exposure | Malabsorption | Gastrectomy or gastrointestinal bypass | Small bowel disease | Pancreatic insufficiency | Defective 25-hydroxylation | Biliary cirrhosis | Alcoholic cirrhosis | Some antiseizure medications | Loss of vitamin D-binding protein | Nephrotic syndrome | Defective 1-alpha-hydroxylation | Hypoparathyroidism | Chronic kidney disease | Vitamin D-dependent rickets, type 1 | Defective target organ response to calcitriol | Vitamin D-dependent rickets, type 2 (hereditary vitamin D-resistant rickets [HVDRR]) | | Mineralization defects | Abnormal matrix | Chronic kidney disease | Osteogenesis imperfecta | Fibrogenesis imperfecta | Axial osteomalacia | Enzyme deficiency | Hypophosphatasia | Inhibitors of mineralization | Fluoride | Aluminium | Some bisphosphonates (eg, etidronate) | Phosphate deficiency | Decreased intake | Antacids | Impaired renal reabsorption | Primary defects | X-linked hypophosphatemic rickets (vitamin D-resistant rickets [VDRR]) | Hereditary hypophosphatemic rickets with hypercalciuria | Sporadic acquired hypophosphatemic rickets | Fanconi syndrome, Wilson disease, cystinosis, multiple myeloma | Secondary defects | Secondary hyperparathyroidism (renal tubular acidosis, type 1 and disorders of vitamin D metabolism) | Tumor-induced osteomalacia | |