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Updated: Jan 18 2022

Rickets / Osteomalacia

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  • Snapshot
    • A 6-year-old boy is brought to his pediatrician by his parents due to poor growth, weakness, and abnormal gait. On physical exam, there is bowing of the legs and tenderness upon palpation of the lower extremity. Laboratory testing is significant for a decreased serum calcium and phosphate levels and elevated parathyroid hormone and serum alkaline phosphatase levels. (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)
  • 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
        • osteomalacia
          • reduced bone mineral density
            • a non-specific finding
          • inability to radiologically distinguish vertebral body trabeculae
            • the film appears poor quality
          • Looser pseudofractures, fissues, or narrow radiolucent lines
            • characteristic radiologic findings
        • rickets
          • perform an anteriorposterior radiograph in skeletal areas that are rapidly growing (e.g., knee or wrist)
            • osteopenia
            • metaphysis may appear frayed and widened
            • distal physis may appear widened
            • bones of the arms and legs may have angular defomities
  • Studies
    • Labs
      • highly dependent on the cause
        • e.g., patients with vitamin D deficiency will have decreased 25-hydroxyvitamin D
    • Laboratory Abnormalities in Rickets/Osteomalacia
      Etiology
      Serum Phosphate
      Serum Calcium
      Serum Alkaline Phosphatase
      Parathydroid Hormone
      Vitamin D deficiency Decreased or normal
        Decreased or normal
          Elevated
            Elevated
              Urinary phosphate wasting Decreased
                Normal
                  Elevated or normal
                    Normal
                      Proximal (type II) renal tubular acidosis Decreased
                        Normal
                          Normal
                            Normal
                              Hypophosphatasia Normal
                                Normal
                                  Decreased
                                    Normal
                                  • Differential
                                    • Child abuse
                                    • Osteoporosis
                                    • Paget disease of bone
                                    • Multiple myeloma
                                    • Vitamin D resistant rickets
                                      • normal vitamin D and normal PTH
                                    • Laboratory Abnormalities in Select Bone Disorders
                                      Etiology
                                      Serum Phosphate
                                      Serum Calcium
                                      Serum Alkaline Phosphatase
                                      Parathyroid Hormone
                                      Osteoporosis
                                      NormalNormal or decreasedNormalNormal
                                      Paget disease of the boneNormalNormalElevatedNormal
                                      Osteitis fibrosa cystica
                                      Primary
                                      hyperparathyroidism
                                      •decreased

                                      Secondary
                                      hyperparathyroidism
                                      •increased

                                        Primary
                                        hyperparathyroidism
                                        •increased

                                        Secondary
                                        hyperparathyroidism
                                        •decreased

                                          Primary and secondary hyperparathyroidism
                                          •increased

                                            Primary and secondary hyperparathyroidism
                                            •increased
                                              Hypervitaminosis DIncreasedIncreasedNormalDecreased
                                          • 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
                                          • Prognosis
                                            • Depends on the etiology
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