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:

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:

Disorder of PTH secretion and action
- Congenital hypoparathyroidism
- Chromosome 22q11.2 deletion: DiGeorge Syndrome (calcium supplementation treatment)
- Acquired causes such as parathyroidectomy
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
Abnormality of calcium sensing receptor

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

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

Calcipenic Rickets: Due to calcium and/or Vitamin D deficiency regardless of the cause
Phosphopenic Rickets: Due to Renal Tubular phosphate deficiency due to either renal loss or nutritional defect
Vitamin D Deficient Rickets