## Vitamin D Deficiency in Indian Children **Key Point:** Vitamin D deficiency is the most common vitamin deficiency in Indian children, particularly in populations with limited sun exposure, dietary inadequacy, and malabsorption. ### Clinical Presentation The child in this vignette presents with classic features of nutritional rickets: - Frontal bossing and delayed fontanelle closure (skeletal manifestations) - Bowing of legs (long bone deformity) - Delayed motor milestones (hypocalcemia and muscle weakness) - Recurrent respiratory infections (immunological compromise) ### Biochemical Markers | Parameter | Finding | | --- | --- | | Serum calcium | Low (hypocalcemia) | | Serum phosphate | Low | | Alkaline phosphatase | Elevated | | 25-OH vitamin D | <20 ng/mL (deficient) | | PTH | Elevated (secondary hyperparathyroidism) | ### Epidemiology in India **High-Yield:** Vitamin D deficiency affects 40–90% of Indian children depending on region, socioeconomic status, and dietary practices. It is endemic in: - Urban populations with limited outdoor exposure - Vegetarian populations (limited dietary sources) - Malabsorption disorders - Exclusively breastfed infants without vitamin D supplementation ### Mechanism of Rickets 1. Low vitamin D → impaired intestinal calcium absorption 2. Hypocalcemia → secondary hyperparathyroidism 3. PTH-driven phosphate wasting → hypophosphatemia 4. Defective bone mineralization → rickets **Clinical Pearl:** Rickets is the most visible end-organ manifestation of vitamin D deficiency in children; in adults, osteomalacia predominates. **Mnemonic — Rickets Features: ABCD** - **A**rticular: frontal bossing, delayed fontanelle - **B**ones: bowing, beading of costochondral junctions - **C**alcium: hypocalcemia, tetany, seizures - **D**elay: motor milestones, growth [cite:Park 26e Ch 8]
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