Vitamin D Deficiency

Definition

Vitamin D deficiency in children is a condition characterized by insufficient levels of vitamin D, leading to impaired bone mineralization, rickets, delayed growth, and increased risk of fractures.

Epidemiology

• Common worldwide, especially in breastfed infants without supplementation
• Higher prevalence in regions with limited sunlight exposure
• More frequent in children with darker skin pigmentation
• Can occur at any age, but peak incidence is in infancy and early childhood
• Associated with malnutrition and chronic illnesses affecting absorption

Etiology

• Insufficient dietary intake or supplementation
• Limited sunlight exposure or use of sunscreen
• Malabsorption syndromes: celiac disease, cystic fibrosis, inflammatory bowel disease
• Liver or kidney disease affecting vitamin D metabolism
• Medications: anticonvulsants, glucocorticoids
• Genetic disorders affecting vitamin D receptor or metabolism (rare)

Pathophysiology

• Low vitamin D levels reduce intestinal calcium and phosphate absorption
• Hypocalcemia and hypophosphatemia impair bone mineralization
• Secondary hyperparathyroidism may develop to maintain serum calcium
• Bone deformities occur due to defective mineralization (rickets in children, osteomalacia in adolescents)
• Delayed growth and musculoskeletal pain result from skeletal abnormalities
• Severe deficiency may cause tetany or seizures due to hypocalcemia