A child was brought with bony deformities, as shown in the radiograph below. It could be due to the deficiency of which of the following? La d

Correct Answer: D. Vitamin D

Vitamin D deficiency in children causes rickets, a metabolic bone disease characterized by defective mineralization of the growth plate and cortical bone. The radiograph described ("La d" notation, likely referring to the classic "Looser's zones" or metaphyseal changes) shows the pathognomonic skeletal deformities of rickets: metaphyseal widening, loss of sharp metaphyseal margins, subperiosteal new bone formation, and cortical thinning. In India, nutritional rickets remains endemic due to inadequate sun exposure, dietary insufficiency, and malabsorption. Vitamin D deficiency impairs intestinal calcium absorption and causes secondary hyperparathyroidism, leading to increased bone resorption and defective mineralization. Clinical features include bowing of long bones (genu varum/valgum), frontal bossing, rachitic rosary (costochondral beading), and delayed fontanelle closure. The biochemical hallmark is elevated alkaline phosphatase, elevated PTH, low 25-OH vitamin D (<20 ng/mL), and hypocalcemia. Treatment involves vitamin D supplementation (600,000 IU weekly for 6 weeks in India per IAP guidelines) and calcium supplementation, with dietary modification and sun exposure counseling.

Why the other options are wrong

A. Vitamin K — Vitamin K deficiency causes coagulopathy (hemorrhagic disease of newborn, bleeding tendency) and does not produce skeletal deformities. While vitamin K is essential for bone matrix proteins (osteocalcin), deficiency manifests as bleeding, not rickets or bony deformities. This is an NBE distractor using bone-related terminology. B. Vitamin A — Vitamin A deficiency causes night blindness, xerophthalmia, and corneal scarring—not skeletal deformities. Excess vitamin A (hypervitaminosis A) can cause bone pain and hyperostosis, but deficiency does not produce rickets or metaphyseal changes. NBE pairs this with 'bone' to trap students unfamiliar with rickets etiology. C. Vitamin C — Vitamin C deficiency causes scurvy, characterized by bleeding gums, poor wound healing, and subperiosteal hemorrhages—not the metaphyseal widening and mineralization defects seen in rickets. Scurvy radiographs show the 'scorbutic rosary' and ground-glass osteopenia, distinct from rachitic changes. This option exploits confusion between scurvy and rickets.

High-Yield Facts

Mnemonics

RICKETS Deformities Rachitic rosary (costochondral beading) | Increased ALP | Cortical thinning | Knee bowing (genu varum/valgum) | Elevated PTH | Thin metaphyseal margins | Subperiosteal new bone Vitamin D Deficiency vs. Scurvy (NBE trap) Rickets = defective mineralization (metaphyseal widening, loss of sharp margins); Scurvy = defective collagen (subperiosteal hemorrhage, ground-glass osteopenia). Rickets = vitamin D; Scurvy = vitamin C.

NBE Trap

NBE pairs "bony deformities" with multiple vitamins to trap students unfamiliar with rickets-specific radiological signs. The key discriminator is metaphyseal widening and loss of sharp margins—unique to rickets, not seen in vitamin A, K, or C deficiency. Students may confuse scurvy (vitamin C) with rickets because both cause bone changes, but scurvy shows subperiosteal hemorrhage and ground-glass osteopenia, not metaphyseal widening.

Clinical Pearl

In India, a child presenting with bowing of legs and delayed motor milestones should raise suspicion for nutritional rickets—the most common preventable cause of skeletal deformity in pediatric practice. Early recognition and vitamin D supplementation per IAP guidelines can prevent permanent deformities and optimize growth and development.

_Reference: Robbins Ch. 8 (Metabolic Bone Disease); Harrison Ch. 395 (Rickets); OP Ghai Ch. 6 (Nutritional Rickets); IAP Clinical Practice Guidelines on Rickets_