Snapshot A 7-year-old girl is brought to the emergency department after experiencing a risk fracture. The patient fell down to the ground and has not hit her head. This has never happened before. The patient's parents reports their child states she has pain in bones and at times feels weak. On physical exam, there is tenderness to palpation of the wrist with a waddling gait. Laboratory testing is notable for a decreased serum calcium and phosphate level, and increased alkaline phosphatase and parathyroid hormone. (Rickets secondary to vitamin D defiency) Introduction Clinical definition osteomalacia a condition due to defective mineralization of osteoid rickets a condition due to defective mineralization of cartilage in the epiphyseal growth plates Epidemiology demographics children can have both osteomalacia and rickets adults can only have osteomalacia since their growth plates have been fused risk factors vitamin D deficiency secondary to poor dietary intake and sun exposure malabsorption e.g., inflammatory bowel disease and gastrointestinal bypass surgery genetic causes that result in vitamin D deficiency and vitamin D resistance primary hypophosphatemia e.g., X-linked hypophosphatemic rickets and autosomal dominant hypophosphatemic rickets Etiology vitamin D deficiency hypophosphatemia chronic kidney disease e.g., metabolic acidosis and decreased 1,25-dihydroxyvitamin D synthesis renal tubular acidosis proximal (type II) renal tubular acidosis/Fanconi syndrome secondary to phosphate wasting, metabolic acidosis which increases calcium loss, and secondary hyperparathyroidism inhibitors of bone mineralization e.g., bisphosphonates, alimunum, and fluoride hypophosphatasia a tissue non-specific alkaline phosphatase (TNSALP) gene mutation that leads to the accumulation of pyrophosphate pyrophosphate inhibits bone mineralization Pathogenesis impaired mineralization of osteoid (osteomalacia) and/or cartilage at the epiphyseal plates (rickets) Prognosis depends on the etiology Presentation Symptoms bone and joint pain muscle weakness difficulty with walking fractures Physical exam pediatric bowed legs rachitic rosary line costochondral thickenings Harrison's groove depression along line of diaphragmatic insertion into rib cage kyphosis as well as lordosis and scoliosis poor growth bone tenderness to palpation Imaging Radiography indication perform in patients with a clinical presentation concerning for osteomalacia or rickets findings radiolucency (decreased bone density) physeal widening metaphyseal cupping prominence of rib heads at the osteochondral junction (rachitic rosary) bowing (often genu varum) Studies Labs highly dependent on the cause e.g., patients with vitamin D deficiency will have decreased 25-hydroxyvitamin D Laboratory Abnormalities in Select Bone Disorders Etiology Serum Phosphate Serum Calcium Serum Alkaline Phosphatase Parathyroid Hormone Osteomalacia/rickets Decreased Decreased Increased Increased Osteoporosis Normal Normal Normal Normal Osteopetrosis Normal Normal or decreased Normal Normal Paget disease of the bone Normal Normal Elevated Normal Osteitis fibrosa cystica Primaryhyperparathyroidism decreased Secondaryhyperparathyroidism increased Primaryhyperparathyroidism increased Secondaryhyperparathyroidism decreased Primary and secondary hyperparathyroidism increased Primary and secondary hyperparathyroidism increased Hypervitaminosis D Increased Increased Normal Decreased Differential Child abuse Osteogenesis imperfecta Osteoporosis Paget disease of bone Multiple myeloma Treatment Medical treatment is directed against the underlying cause for example vitamin D supplemention indication in patients with vitamin D deficiency hereditary hypophosphatemic rickets along with phosphate supplementation osteomalacia of renal tubular acidosis along with sodium or potassium citrate Complications Fractures Growth abnormalities