Rickets

Pediatrics Rickets

Dr Faten Zaidan

Introduction

Calcium balance is achieved by calcium transport across three organ systems: intestines, kidney, bone through the effect of two hormones:

• PTH and 1,25 dihydroxy vitamin D

A fall in calcium level is detected in parathyroid glands and renal tubules therefore increasing PTH and active Vitamin D. This leads to:

• Increased renal tubular reabsorption of calcium and decreased tubular reabsorption of phosphate and increased phosphate excretion. This is called the phosphaturic effect.
• Increased bone resorption leading to calcium release from bone into circulation.
• Stimulation of 1 alpha hydroxylase activity at the proximal renal tubule which results in increased secretion of 1.25(OH)2D and increased reabsorption of intestinal calcium.

Hypocalcemia can result from three categories of disorders:

1. Disorder of PTH secretion and action

   • Congenital hypoparathyroidism
   • Chromosome 22q11.2 deletion: DiGeorge Syndrome (calcium supplementation treatment)
   • Acquired causes such as parathyroidectomy

2. Disorders of vitamin D deficiency or action

   • Renal disease > 1 alpha hydroxylase deficiency or renal disease
   • 25-hydroxylase deficiency or liver disease
   • Vitamin D resistance

3. Abnormality of calcium sensing receptor

Causes of Hypocalcemia as per Age

Neonatal

• Early (0-72 hours)

  • Preterm
  • LBW
  • RDS (initially only)
  • Asphyxia
  • Acidosis
  • Infants of diabetic mothers
  • Exchange plasma transfusion

• Late (after 72 hours)

  • High phosphate milk
  • Vit D deficiency
  • Hypoparathyroidism
  • Maternal hyperparathyroidism
  • Mg deficiency

Later in Childhood

• VD Deficiency
• VD Metabolism Problems
• Hypoparathyroidism
• Calcium Deficiency
• Hypomagnesemia
• High Phosphate (e.g., enemas/tumor lysis syndrome)

Presentation of hypocalcemia

• Hypocalcemia

Type of rickets

Rickets is under-mineralization of the growth plate of a growing bone due to abnormality in the production or excretion of calcium and phosphate.

1. Calcipenic Rickets: Due to calcium and/or Vitamin D deficiency regardless of the cause

2. Phosphopenic Rickets: Due to Renal Tubular phosphate deficiency due to either renal loss or nutritional defect

3. Vitamin D Deficient Rickets

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Orthopedics

Rickets & Osteomalacia

Overview

• Same disease process affecting different age groups:
  • Rickets: Children (growing skeleton)
  • Osteomalacia: Adults (mature skeleton)
• Pathophysiology: Inadequate absorption and/or utilization of $\text{Ca}$
• Common causes:
  • Lack of Vitamin D → Severe $\text{Ca}$ deficiency
  • Hypophosphatemia
• Result: Loss of mineralization of bone matrix

RicketsZ

Pathology

• Matrix forms but is not calcified (soft bone)
• In growing physis:
  • Widened physis (epiphyseal growth plate)
  • Cupping of metaphyseal end (weak new bone)
  • Irregular metaphyseal end
• In all bone:
  • Osteopenia (decreased bone density)
  • Thin cortex
  • Deformity

Clinical PictureZ

Skeletal Manifestations

• Enlarged ends of long bones:
  • Wrists and knees most prominent
• Rickety rosary: Enlarged costo-chondral junctions
• Harrison’s sulcus: Horizontal groove at lower border of thorax
• Frontal bossing: Prominent forehead

Lower Limb Deformities

• Bowing of legs: most common presentation
  • Localized – distal tibiae most affected

Systemic Symptoms (in severe cases)

• Tetany and convulsions (due to hypocalcemia)

Additional Clinical Signs

Harris’s sign (subluxation of costochondral junctions)

Rickety Rosary

Radiological Features

Primary X-ray Findings

• Widened physis (first and most prominent finding)
• Metaphyseal changes:
  • Cupping (due to weak new bone)
  • Irregular margins
  • Deformed bones

Laboratory Results

Parameter	Expected Findings
Serum Calcium	Slightly low or normal
Serum Phosphate	Slightly low or normal
Serum Alkaline Phosphatase	High (increased bone turnover)
Serum Vitamin D	Low
Serum PTH	Increased (secondary effect to maintain serum Ca)
Urinary Calcium	Very low

Treatment

Primary Management ✓

• Vitamin D supplementation
• Calcium supplementation

Management of Deformities

• Most deformities correct gradually with medical treatment
• Severe deformities may require surgical correction

Hypophosphatemic Rickets

Overview

• Vitamin D resistant rickets
• Familial, X-linked inheritance
• Renal tubular acidosis → need very high doses of Ca²⁺

Pathophysiology

• Impaired renal tubular reabsorption of phosphate

Laboratory Results

Parameter	Finding
Serum Phosphate	Low
Urinary Phosphate	High

Treatment

• High dose Vitamin D
• Phosphate supplementation