questions 2

Rickets / Osteomalacia

Topic updated on 09/04/17 1:08pm

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)
  • 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
      • 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
  • Osteogenesis imperfecta
  • Osteoporosis
  • Paget disease of bone
  • Multiple myeloma
 
Laboratory Abnormalities in Select Bone Disorders
Etiology
Serum Phosphate
Serum Calcium
Serum Alkaline Phosphatase
Parathyroid Hormone
Osteoporosis
  • Normal
  • Normal or decreased
  • Normal
  • Normal
Paget disease of the bone
  • Normal
  • Normal
  • Elevated
  • Normal
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 D
  • Increased
  • Increased
  • Normal
  • Decreased
 
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


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AVERAGE 4.0 of 4 RATINGS

Qbank (1 Questions)

TAG
(M2.OR.17) During the well exam of an otherwise healthy two-year-old African-American male, you note the deformity seen in Figure A. Lab results are as follows: Serum Calcium = 9.1 mg/dL (N=8.4-10.2), Phosphorus = 1.1 mg/dL (N=3.8-6.2), Alkaline Phosphatase = 462 U/L (N=68-217), PTH = 23 pg/mL (N=10-55), 1,25-dihydroxyvitamin D = 22 pmol/L (N=15-30). What is the most likely cause of his deformity? Topic Review Topic
FIGURES: A          

1. Vitamin D Resistant Rickets
2. Vitamin D Deficiency Rickets
3. Type II Vitamin D Dependent Rickets
4. Pseudohypoparathyroidism
5. Renal Osteodystrophy

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