Rickets: Clinical Case Discussion and Key Learning Points
Model Case Presentation
Patient Demographics
Name: Master Rohan, Age: 18 months, Gender: Male, Informant: Mother (Reliable)
Chief Complaints
- Bowing of legs noticed since he started walking – 4 months
- Delayed walking – started at 16 months
- Swelling at wrists and knees – 3 months
- Frequent falls and irritability
History Summary
Exclusively breastfed for 12 months with no vitamin D supplementation. Lives in a joint family, stays indoors most of the day; rarely exposed to sunlight. Mother is vegetarian and wore full-covering clothing during pregnancy. Weaning started at 6 months with home-cooked cereal-based diet, poor in dairy. No history of seizures, tetany, or loss of consciousness. No history of jaundice, chronic diarrhea, or recurrent infections. Milestones: Held head at 5 months, sat at 10 months, walked at 16 months (delayed). No family history of bone disease or consanguinity.
Born at term via NVD, birth weight 2.9 kg. Antenatal period: Mother had minimal sun exposure, no vitamin D supplementation during pregnancy.
Examination Summary
| Parameter | Finding | Significance |
|---|---|---|
| Weight | 8.5 kg | Mild underweight (expected ~11 kg) |
| Height | 74 cm | Stunted (expected ~82 cm) |
| Head circumference | 48 cm | Normal; frontal bossing noted |
| Temperature | Afebrile | — |
| Pallor | Mild | Nutritional anemia |
| Jaundice/Cyanosis | Absent | — |
Skull: Frontal and parietal bossing giving a "hot cross bun" appearance. Anterior fontanelle open (3×3 cm). Craniotabes absent (18 months — present mainly in infants < 6 months).
Teeth: Delayed dentition — only 4 teeth present (expected 12 by 18 months).
Chest: Rachitic rosary (beading at costochondral junctions bilaterally). Harrison's sulcus (horizontal groove at lower chest corresponding to diaphragm insertion).
Abdomen: Pot belly (protuberant abdomen). Mild hepatomegaly. Hypotonic abdominal musculature.
Limbs: Genu varum (bow legs) bilaterally. Widening and swelling of wrists and ankles (metaphyseal expansion). Waddling gait. Hypotonia present. Intercondylar distance > 3 cm.
✅ Complete Diagnosis
Nutritional Rickets — Vitamin D Deficiency Rickets (Calcipenic) in a 18-month-old male with Genu Varum, Harrison's Sulcus, Rachitic Rosary, and Failure to Thrive; with secondary Hyperparathyroidism.
📝 History — Exam Q&A
Rickets is a disease of growing children characterized by impaired mineralization of the growth plate cartilage and osteoid, resulting from defects in calcium and phosphate homeostasis. The fundamental defect is failure of calcification of osteoid at the growth plate, leading to accumulation of uncalcified osteoid, widening of the growth plate, and bone deformities.
💡 Rickets vs Osteomalacia
Rickets = defective mineralization of growth plate + bone matrix → occurs only in children (open growth plates). Osteomalacia = defective mineralization of bone matrix only → occurs in adults and children.
Nutritional rickets due to Vitamin D deficiency is the most common type globally.
Risk factors:
- Exclusive breastfeeding without Vitamin D supplementation (breast milk is low in Vitamin D)
- Dark skin pigmentation (reduced UV-mediated Vitamin D synthesis)
- Minimal sunlight exposure (indoor lifestyle, full-body clothing, high latitude)
- Maternal Vitamin D deficiency during pregnancy/lactation
- Low birth weight / preterm infants
- Vegetarian diet, low dietary calcium intake
- Malabsorption syndromes (celiac disease, cystic fibrosis, cholestatic liver disease)
- Chronic antiepileptic drug use (phenytoin, phenobarbitone — accelerate Vitamin D catabolism)
Normal pathway: Skin (UV) → Cholecalciferol (D3) → Liver (25-hydroxylation) → 25(OH)D (Calcidiol, storage form) → Kidney (1α-hydroxylation) → 1,25(OH)₂D (Calcitriol, active form) → Intestinal calcium & phosphate absorption ↑.
In Vit D deficiency:
- Calcitriol ↓ → Intestinal Ca²⁺ and PO₄ absorption ↓
- Serum Ca²⁺ falls → PTH secretion ↑ (secondary hyperparathyroidism)
- PTH → Renal Ca²⁺ reabsorption ↑ (normalizes calcium) + Renal PO₄ excretion ↑ (worsens hypophosphatemia)
- Low Ca²⁺ + Low PO₄ → Failure of mineralization → Rickets
- Hypophosphatemia is the final common pathway leading to growth plate widening
| Category | Type | Mechanism |
|---|---|---|
| Calcipenic (Low Ca²⁺ driven) | Nutritional Vit D deficiency | ↓ Dietary/sun Vit D |
| Vitamin D-Dependent Rickets Type 1 (VDDR-I) | ↓ 1α-hydroxylase (CYP27B1 mutation) | |
| Vitamin D-Dependent Rickets Type 2 (VDDR-II) | VDR receptor mutation (end-organ resistance) | |
| Phosphopenic (Low PO₄ driven) | X-linked Hypophosphatemic Rickets (XLH) | FGF23 excess → renal PO₄ wasting (PHEX mutation) |
| Autosomal Recessive/Dominant Hypophosphatemic Rickets | FGF23-related PO₄ wasting | |
| Fanconi Syndrome / Renal Tubular Acidosis | Generalized tubular dysfunction → PO₄ wasting | |
| Other | Calcium deficiency rickets | Low dietary calcium (independent of Vit D) |
💡 Key
In calcipenic rickets, serum calcium is low/normal with elevated PTH. In phosphopenic rickets, serum calcium is normal and PTH is normal/mildly elevated.
| Age Group | Predominant Features |
|---|---|
| < 6 months (Infants) | Craniotabes, hypocalcemic seizures/tetany, frontal bossing, delayed fontanelle closure, irritability, occipital alopecia |
| 6–18 months | Rachitic rosary, Harrison's sulcus, delayed dentition, hypotonia, pot belly, delayed motor milestones |
| > 18 months (Toddlers/weight-bearing) | Genu varum (bow legs), genu valgum (knock knees), widened wrists/ankles, waddling gait, coxa vara, pathological fractures |
| Adolescents | Vague bone pain, muscle weakness, stress fractures — florid signs are rare |
💡 Why bow legs in toddlers?
When the child starts weight-bearing, the softened long bones bow under gravitational stress. Before weight-bearing, craniotabes and chest deformities predominate. After weight-bearing, leg deformities predominate.
- Feeding history: Exclusive breastfeeding? Duration? Vitamin D supplementation started? Weaning foods and dairy intake?
- Sunlight exposure: Time outdoors? Use of full-body clothing? City/rural residence? Latitude?
- Maternal history: Vit D supplementation during pregnancy? Maternal diet (vegetarian)? Sun exposure? Dark skin?
- Birth history: Preterm? LBW? (Higher risk)
- Drug history: Antiepileptics (phenytoin, phenobarbitone)? Cholestyramine?
- Symptoms: Seizures/tetany (hypocalcemia)? Bone pain? Fractures without major trauma?
- Family history: Short stature, bone deformities in parents/siblings? (Suggests inherited forms like XLH)
- GI history: Chronic diarrhea, steatorrhea (malabsorption)?
- Milestones: Delayed motor milestones due to hypotonia?
- Inheritance: X-linked dominant (PHEX mutation) — maternal family history of short stature, bow legs
- Onset: Presents when child starts to walk (12–18 months) with prominent leg bowing
- No hypocalcemic symptoms (no seizures or tetany) — calcium is normal
- Dental abscesses: Multiple, recurrent without caries (pathognomonic for XLH due to hypomineralized dentin)
- Poor response to normal doses of Vit D — was historically called "Vit D Resistant Rickets"
- Short stature disproportionate (short legs, normal trunk)
- No features of Vit D deficiency (adequate sun exposure, no malabsorption)
| Stage | Biochemistry | Symptoms |
|---|---|---|
| Stage I | Ca²⁺ ↓, PO₄ ↓, PTH ↑, ALP ↑, 25(OH)D ↓ | Hypocalcemic symptoms: seizures, tetany, stridor, apnea |
| Stage II | Ca²⁺ normal (PTH compensates), PO₄ ↓↓, PTH ↑↑, ALP ↑↑ | Skeletal deformities appear; classic radiological rickets |
| Stage III | Ca²⁺ ↓, PO₄ ↓↓, PTH ↑↑↑, ALP ↑↑↑ | Severe bone disease + hypocalcemia coexist |
🩺 Examination — Exam Q&A
Head:
- Craniotabes — softening/thinning of skull bones (occipital & parietal); "ping-pong ball" sensation on pressure; earliest sign in infants < 6 months
- Frontal and parietal bossing — protuberant forehead; "hot cross bun" skull appearance
- Delayed closure of anterior fontanelle (normally closes by 18 months)
- Delayed dentition with defective enamel
- Dolichocephaly (elongated skull)
Chest:
- Rachitic rosary — beading of costochondral junctions (most sensitive physical sign); widened metaphysis at rib ends
- Harrison's sulcus — horizontal groove at the lower border of the chest wall, at the level of diaphragm attachment; caused by inward pull of the soft ribs by the diaphragm
- Pigeon chest / Pectus carinatum — forward protrusion of the sternum
- Subcostal recession — inward retraction at costal margin
Spine:
- Kyphoscoliosis
- Lumbar lordosis (from hypotonic abdomen and gluteal muscles)
Limbs:
- Widening of wrists and ankles — metaphyseal expansion (most common clinical sign overall)
- Genu varum (bow legs) — in early weight-bearing children
- Genu valgum (knock knees) — more common in older children/adolescents
- Coxa vara — causes waddling gait
- Pathological fractures — green-stick fractures
Abdomen:
- Pot belly — due to hypotonia of abdominal muscles and hepatosplenomegaly
Craniotabes is softening and thinning of the skull bones, particularly the occipital and parietal bones, due to demineralization.
How to elicit: Apply firm pressure with fingertips over the occipital and parietal bones. Positive result: inward collapse followed by a snapping back (like pressing a ping-pong ball).
Significance: Earliest sign of rickets in infants < 6 months. However, mild craniotabes may be physiological in neonates up to 3 months. It is pathological if persistent beyond 3–4 months or associated with other features.
Harrison's sulcus is a horizontal groove along the lower border of the thorax, corresponding to the attachment of the diaphragm to the lower ribs.
Mechanism: The softened, demineralized ribs are pulled inward during normal diaphragmatic contraction (inspiration). Over time, this causes a permanent inward groove. It may also be seen in any condition causing chronic respiratory difficulty with increased work of breathing in a child with soft ribs (e.g., chronic asthma).
| Feature | Rachitic Rosary (Rickets) | Scorbutic Rosary (Scurvy) |
|---|---|---|
| Mechanism | Metaphyseal widening at costochondral junction | Subperiosteal hemorrhage at costochondral junction |
| Feel | Soft, non-tender | Hard, very tender/painful |
| Location | At the costochondral junction itself | Prominent just lateral to the junction |
| Step | No sharp step-off | Sharp "bayonet" step-off |
| Associated | Bone deformities, low Vit D | Bleeding gums, perifollicular hemorrhages, low Vit C |
Genu varum (bow legs): The knees are separated when the feet/ankles are together. Measured by intercondylar distance (distance between medial femoral condyles with ankles touching). Pathological if > 3 cm beyond 2 years of age.
Genu valgum (knock knees): The ankles are separated when the knees are together. Measured by intermalleolar distance (distance between medial malleoli with knees touching). Pathological if > 8–9 cm beyond 7 years.
💡 Age Clue
Genu varum is more common in younger children (< 2 years, early weight-bearing). Genu valgum is more common in older children (2–7 years). Physiological genu valgum peaks at ~3.5 years and spontaneously resolves by 7 years.
- Hypocalcemic manifestations: Seizures (commonest presentation in infants), tetany, positive Chvostek's sign (twitching of facial muscles on tapping the facial nerve), positive Trousseau's sign (carpopedal spasm on inflating BP cuff), laryngospasm (stridor)
- Proximal myopathy: Hypotonia, muscle weakness, waddling gait, difficulty climbing stairs
- Failure to thrive / growth retardation
- Occipital alopecia — due to sweating from head (early infancy)
- Anemia — associated nutritional deficiency
- Delayed developmental milestones — motor milestones delayed due to hypotonia and bone pain
- Dilated cardiomyopathy — rare, severe Vit D deficiency
- Immune deficiency — increased susceptibility to respiratory infections
Chvostek's sign: Tap the facial nerve just anterior to the ear (over the parotid gland). Positive: ipsilateral twitching of facial muscles (corner of mouth, nose, eye). Indicates latent hypocalcemic tetany. Note: Mildly positive in up to 10% of normal newborns.
Trousseau's sign (more specific): Inflate a sphygmomanometer cuff on the upper arm to 20 mmHg above systolic BP for 3 minutes. Positive: carpal spasm (obstetrician's hand — flexion of wrist and metacarpophalangeal joints, extension of IP joints, thumb adduction). More specific for hypocalcemia than Chvostek's sign.
| Feature | Nutritional Rickets | XLH (Vitamin D-Resistant Rickets) |
|---|---|---|
| Age of onset | Infancy–toddler | When starts walking (~1–2 years) |
| Hypocalcemic signs | Present (Chvostek/Trousseau, seizures) | Absent |
| Leg deformities | Present (varum/valgum) | Prominent, often severe bow legs |
| Stature | Proportionate short stature | Disproportionate (short legs, normal trunk) |
| Dental abscesses | Absent | Multiple, recurrent (pathognomonic) |
| Craniotabes/rosary | Common | Less common |
| Family history | Often absent | Present (X-linked dominant — mother affected) |
Overt tetany: Carpopedal spasm, laryngospasm (stridor, respiratory distress), convulsions.
Latent tetany (subclinical):
- Chvostek's sign (facial nerve hyperexcitability)
- Trousseau's sign (carpal spasm on BP cuff)
- Erb's sign (hyperexcitability of motor nerves to galvanic stimulation)
- Peroneal sign (eversion of foot on tapping peroneal nerve)
In infants, laryngospasm and hypocalcemic seizures are the most dangerous presentations and may be the presenting feature before skeletal signs appear.
🔬 Investigations — Exam Q&A
- Serum Calcium (Ca²⁺): Low or normal (PTH compensates in Stage II)
- Serum Phosphate (PO₄): Low (invariably — hallmark of all active rickets)
- Serum Alkaline Phosphatase (ALP): Elevated — marker of osteoblast activity; most reliable and consistently raised parameter; must interpret with age-specific norms
- Serum PTH: Elevated (secondary hyperparathyroidism in calcipenic forms; normal/mildly elevated in phosphopenic forms)
- Serum 25(OH)D (Calcidiol): Gold standard for assessing Vitamin D status; < 20 ng/mL = deficiency; < 10 ng/mL = severe deficiency
| Parameter | Nutritional Vit D Deficiency | VDDR Type I (CYP27B1 ↓) | VDDR Type II (VDR mutation) | XLH (Phosphopenic) |
|---|---|---|---|---|
| Serum Ca²⁺ | ↓ or N | ↓ or N | ↓ or N | N |
| Serum PO₄ | ↓ | ↓ | ↓ | ↓↓ (prominent) |
| ALP | ↑↑ | ↑↑ | ↑↑ | ↑↑ |
| PTH | ↑ | ↑ | ↑ | N or slightly ↑ |
| 25(OH)D | ↓↓ | N or ↑ | N or ↑ | N |
| 1,25(OH)₂D | ↓ or N | ↓↓ | ↑↑ (resistance) | N or ↓ |
| Urine Ca | ↓ (low) | ↓ | ↓ | N or ↑ |
| Urine PO₄ | ↓ | ↓ | ↓ | ↑↑ (wasting) |
| FGF23 | N | N | N | ↑↑ |
💡 VDDR II clue
VDDR Type II (end-organ resistance) = very high 1,25(OH)₂D levels + alopecia totalis (in ~50% of cases) — alopecia indicates VDR dysfunction in hair follicles.
Best views: AP radiograph of the wrist (distal radius and ulna) and knee — areas of most rapid bone growth.
X-ray findings (in order of severity):
- Widening of growth plate (epiphyseal plate) — earliest radiological sign
- Cupping and fraying of metaphysis — metaphyseal ends appear widened, concave (cup-shaped) and irregular (frayed/paint-brush appearance)
- Osteopenia — generalized decreased bone density
- Loss of zone of provisional calcification (ZPC)
- Bowing of long bones (femur, tibia) — in weight-bearing children
- Pathological (green-stick) fractures
- Coxa vara on pelvis X-ray
💡 X-ray Signs — Mnemonic: "WCF-OB"
Widening of growth plate → Cupping and fraying of metaphysis → Frayed (paint-brush) appearance → Osteopenia → Bowing
- Urine calcium/creatinine ratio: Low in Vit D deficiency (< 0.1); used to monitor treatment response
- Urine phosphate / TmP/GFR (Tubular Maximum Phosphate/GFR): Low TmP/GFR indicates renal phosphate wasting (XLH, Fanconi syndrome)
- Urine glucose, amino acids, uric acid, pH: To detect Fanconi syndrome (generalized tubular dysfunction)
- Renal function tests (BUN, Creatinine): To rule out renal osteodystrophy (CKD-MBD)
- Liver function tests: To rule out hepatic rickets (↓ 25-hydroxylation)
- FGF23 levels: Elevated in XLH and FGF23-related phosphopenic rickets
- Genetic testing: PHEX mutation analysis for XLH; CYP27B1 for VDDR-I; VDR mutation for VDDR-II
- Serum 1,25(OH)₂D: Low in VDDR-I; elevated in VDDR-II; helps differentiate
The earliest sign of healing is the appearance of a line of provisional calcification (LPC) — a dense white line at the metaphyseal margin, appearing within 2–4 weeks of starting Vitamin D therapy. This is followed by:
- Progressive regularization and sharpening of the metaphyseal margins
- Reduction in widening of the growth plate
- Increasing bone density (remineralization)
- Reduction in bowing over months
Complete radiological healing typically occurs within 3–6 months. Biochemically, ALP starts falling within 4–6 weeks of therapy.
| 25(OH)D Level | Status |
|---|---|
| < 10 ng/mL (< 25 nmol/L) | Severe deficiency — rickets likely |
| 10–20 ng/mL (25–50 nmol/L) | Deficiency |
| 20–30 ng/mL (50–75 nmol/L) | Insufficiency |
| 30–100 ng/mL (75–250 nmol/L) | Sufficiency (optimal) |
| > 150 ng/mL (> 375 nmol/L) | Toxicity risk — hypercalcemia |
💡 Note
25(OH)D (Calcidiol) is the measurement of Vitamin D status — it reflects stores. 1,25(OH)₂D (Calcitriol) reflects active hormone level and may be normal/elevated due to PTH stimulation even in deficiency states.
| Parameter | Nutritional Rickets | Renal Osteodystrophy (CKD) |
|---|---|---|
| Serum Creatinine | Normal | Elevated |
| Serum Calcium | ↓ or N | ↓ (or N with treatment) |
| Serum Phosphate | ↓ | ↑↑ (retention due to low GFR) |
| PTH | ↑ (secondary) | ↑↑ (secondary/tertiary) |
| 25(OH)D | ↓↓ | N or low |
| 1,25(OH)₂D | ↓ or N | ↓↓ (reduced 1α-hydroxylase in diseased kidney) |
| Treatment | Cholecalciferol / D3 | Calcitriol (active form, bypasses kidney) |
💊 Management — Exam Q&A
1. Daily Oral Vitamin D (Cholecalciferol / D3 preferred):
- Newborns < 1 month: 1,000 IU/day
- Infants 1–12 months: 1,000–5,000 IU/day
- Children > 1 year: 5,000–10,000 IU/day
- Duration: Minimum 12 weeks (3 months), until radiological healing confirmed
- After healing: Maintenance 400–1,000 IU/day
2. Stoss Therapy (Single dose / Intermittent high dose):
- Single oral dose: 100,000–600,000 IU (divided into 4–6 oral doses in one day OR IM injection)
- Used when compliance is a concern
- After stoss: start maintenance 400–1,000 IU/day
- Risk: Hypercalcemia — monitor serum calcium
3. Calcium supplementation (essential):
- 30–75 mg/kg/day elemental calcium in 3 divided doses, OR ensure dietary calcium ≥ 500 mg/day
- Prevents "hungry bone" syndrome (worsening hypocalcemia as PTH normalizes after Vit D starts)
🚨 Hungry Bone Syndrome
When Vitamin D treatment begins, the bones rapidly start remineralizing ("hungry bones") → serum calcium drops sharply → severe hypocalcemia, seizures. Prevented by co-administering calcium supplements at the start of treatment.
Emergency management (ABCDE first):
- IV Calcium Gluconate 10%: 0.5 mL/kg (max 10–20 mL) slow IV over 5–10 minutes with cardiac monitoring (risk of bradycardia/asystole if given rapidly)
- Followed by IV calcium infusion: 0.5–1 mmol/kg/day elemental calcium until oral feeds established
- Once stable and feeding: Oral calcium supplements started
- Anti-seizure medication only if seizure persists after calcium correction (most hypocalcemic seizures stop with calcium)
- Vitamin D (oral/IM) started once acute hypocalcemia is controlled
- Do NOT give Vitamin D first without calcium — will worsen hypocalcemia (hungry bone)
Stoss therapy = single-day, high-dose oral Vitamin D administration (100,000–600,000 IU) for treatment of nutritional rickets.
Advantages:
- Overcomes compliance issues (single dose, no daily regimen)
- Useful in areas with poor follow-up or in patients with malabsorption (IM route)
- Equal efficacy to daily therapy in most studies
- Can help differentiate nutritional from familial hypophosphatemic rickets (FHR): In nutritional rickets, serum phosphate rises within 96 hours of stoss — does not occur in FHR
Disadvantages/Cautions:
- Risk of hypercalcemia (especially at higher doses)
- Requires calcium supplementation to prevent hungry bone
- Not recommended as routine first-line by recent guidelines — preferred in compliance-poor settings
- Avoid in patients with granulomatous diseases (sarcoidosis) — risk of severe hypercalcemia
Conventional Treatment (older approach):
- Oral phosphate supplementation (20–60 mg/kg/day elemental phosphate in 4–6 divided doses) — frequent dosing needed due to short half-life
- Calcitriol [1,25(OH)₂D]: 20–30 ng/kg/day in 2 divided doses — to enhance intestinal phosphate and calcium absorption and suppress PTH
- Calcitriol used because the kidney's ability to activate Vit D is impaired (FGF23 inhibits 1α-hydroxylase)
- Regular monitoring: Renal ultrasound (nephrocalcinosis), serum calcium, PTH, renal function
Novel targeted therapy:
- Burosumab — anti-FGF23 monoclonal antibody; directly blocks excess FGF23 → restores renal phosphate reabsorption; approved for XLH in children ≥ 1 year; now preferred first-line for pediatric XLH in many countries
VDDR Type I (CYP27B1 mutation — failure to produce 1,25(OH)₂D):
- Calcitriol [1,25(OH)₂D] — 0.25–2 µg/day orally (bypasses the defective 1α-hydroxylase step)
- OR Alfacalcidol (1α-hydroxyvitamin D₃) — 0.05–0.1 µg/kg/day (requires only hepatic activation)
- Lifelong treatment required
- Calcium supplementation as needed
VDDR Type II (VDR mutation — end-organ resistance to calcitriol):
- Requires very high doses of calcitriol (2–6 µg/day or more) to overcome resistance
- High-dose calcium supplementation — including IV calcium infusion in severe cases
- Some cases respond only to long-term IV calcium infusion; this can allow healing even with persistent VDR defect
- Alopecia does NOT respond to treatment (hair follicle VDR resistance)
- Medical treatment (Vit D + calcium) should be optimized first — most skeletal deformities regress with treatment if child is young and growth plates are open
- Indications for surgical intervention:
- Persistent deformities (genu varum/valgum) that do not correct after growth plates normalize radiologically and biochemistry is normal
- Severe angular deformities causing functional impairment
- Age-inappropriate deformity (> 7 years, genu valgum; > 2 years, severe genu varum)
- Procedures: Corrective osteotomy (most common); guided growth (hemiepiphysiodesis) using 8-plates in growing children — less invasive, reversible
- Rule: Surgery should NOT be performed while rickets is biochemically active — bones are soft, wound healing is poor, deformity will recur
IAP Guidelines (Indian Academy of Pediatrics) 2017:
- All infants: 400 IU/day of Vitamin D3 from the first week of life, irrespective of feeding method, until 1 year of age
- Children 1–18 years: 600 IU/day (if adequate sunlight and diet not ensured)
- Pregnant and lactating mothers: 600 IU/day (reduces maternal and neonatal stores)
- Preterm / LBW infants: 400–1,000 IU/day from birth until 1 year corrected age
- Calcium supplementation: If dietary calcium intake is inadequate (< 250–500 mg/day), supplement 250–500 mg/day calcium in infancy
Non-pharmacological:
- Sunlight exposure: 30 minutes/week if mostly clothed; 2 hours/week if only face/hands exposed (light skin); longer for dark skin
- Dietary sources: Fortified milk, fatty fish, egg yolk
- Food fortification programs
- Earliest signs of response (2–4 weeks): Serum phosphate rises; urinary calcium/creatinine ratio becomes detectable (was near zero); clinical irritability improves
- Biochemical response (4–6 weeks): Calcium normalizes; ALP starts to fall (reaches normal by 3 months)
- Radiological response (2–4 weeks): Line of provisional calcification appears at metaphysis — earliest radiological sign of healing
- 3-month review: Repeat X-ray wrist + serum Ca, PO₄, ALP, PTH; if healed, switch to maintenance dose
- Clinical response: Skeletal deformities improve slowly over months; full resolution may take 1–2 years depending on age
- Hypocalcemic complications: Seizures, tetany, laryngospasm, apnea, cardiac arrhythmias, dilated cardiomyopathy
- Skeletal: Permanent bone deformities (genu varum/valgum, kyphoscoliosis), coxa vara, short stature, pathological fractures, pelvic deformity (dystocia in females)
- Respiratory: Chest deformity → restrictive lung disease; Harrison's sulcus; increased susceptibility to respiratory infections (immune deficiency from Vit D)
- Dental: Defective enamel, delayed dentition, increased caries
- Neurological: Hypotonia, delayed motor milestones, muscle weakness
- Hematological: Anemia, rarely myelofibrosis (with severe Vit D deficiency)
- Long-term: Osteoporosis in adulthood, increased fracture risk
🔭 Recent Advances — Exam Q&A
Burosumab is a fully human monoclonal antibody targeting FGF23 (Fibroblast Growth Factor 23). It is used in the treatment of X-linked Hypophosphatemic Rickets (XLH).
Mechanism: FGF23 is overproduced due to PHEX mutations in XLH → FGF23 inhibits renal phosphate reabsorption (via NaPi-2a/c transporters) and suppresses 1α-hydroxylase → hypophosphatemia + low calcitriol. Burosumab blocks FGF23 → restores renal phosphate reabsorption → corrects hypophosphatemia.
Administration: Subcutaneous injection every 2 weeks (in children ≥ 1 year).
Advantages over conventional therapy:
- More physiological correction of phosphate (less hypercalciuria, nephrocalcinosis)
- Better radiological healing and growth
- Fewer daily doses required (vs oral phosphate 4–6x/day)
Side effects: Injection site reactions, headache, limb pain, transient hypercalcemia.
Recent evidence (2022–2024 guidelines) emphasizes that hypophosphatemia is the direct cause of impaired growth plate apoptosis regardless of the primary etiology:
- In calcipenic rickets: PTH-driven phosphaturia → secondary hypophosphatemia → growth plate failure
- In phosphopenic rickets: Primary renal phosphate wasting → hypophosphatemia → identical growth plate failure
- This explains why both calcipenic and phosphopenic rickets share similar radiological features despite different initial mechanisms
- Implication: Correcting hypophosphatemia (not just calcium or Vitamin D) is critical for healing of the growth plate
- Immune modulation: VDR expressed in immune cells; Vit D deficiency linked to increased susceptibility to respiratory infections, tuberculosis, and sepsis
- Autoimmune disease: Low Vit D associated with increased risk of type 1 diabetes mellitus, multiple sclerosis, inflammatory bowel disease
- Cardiovascular: Vit D deficiency linked to dilated cardiomyopathy, heart failure in children (rare but reversible with Vit D treatment)
- Neurodevelopment: VDR expressed in brain; prenatal Vit D deficiency linked to neurodevelopmental outcomes (autism, schizophrenia — associations under study)
- Oncology: Antiproliferative effects; low Vit D associated with increased cancer risk in population studies
💡 Exam note
While non-skeletal roles are emerging, skeletal outcomes remain the primary indication for Vit D supplementation and treatment in children. Non-skeletal benefits are not yet confirmed by RCTs for supplementation in replete individuals.
Hypophosphatasia (HPP) is a rare inherited metabolic bone disease caused by loss-of-function mutations in the ALPL gene encoding tissue-nonspecific alkaline phosphatase (TNSALP).
Why it mimics rickets: Deficient ALP activity → failure of bone mineralization (ALP normally cleaves pyrophosphate, which inhibits mineralization) → rachitic-like skeletal changes on X-ray.
Key distinguishing feature: In rickets, ALP is elevated. In hypophosphatasia, ALP is very low or absent — this is the diagnostic clue.
Other features: Premature loss of deciduous teeth before age 5 (before root resorption), pathological fractures, muscle weakness, hypercalciuria (nephrocalcinosis).
Treatment: Asfotase alfa — enzyme replacement therapy (recombinant ALP); approved for severe perinatal, infantile, and childhood HPP.
The Global Consensus Recommendations on Prevention and Management of Nutritional Rickets (Munns et al., 2016 — JCEM) is the landmark multi-society guideline. Key recommendations:
- All infants should receive 400 IU/day Vitamin D from birth
- Confirmed nutritional rickets: treat with daily oral Vit D + calcium for minimum 12 weeks
- Stoss therapy is acceptable when compliance is poor
- Calcium must be given simultaneously to prevent hungry bone syndrome
- Radiographic evidence of healing required before reducing to maintenance
- Screen siblings and mothers for Vit D deficiency
- Emphasizes that calcium deficiency (not just Vit D deficiency) is an independent cause of rickets — particularly common in African and Asian countries
⚡ Key Points — Quick Revision
One-Liners for Exam
- Most common rickets: Nutritional (Vitamin D deficiency)
- Fundamental defect: Impaired mineralization of growth plate → hypophosphatemia is the final common pathway
- Earliest sign in infants (< 6 months): Craniotabes
- Most sensitive clinical sign (all ages): Rachitic rosary + widened wrists
- Best X-ray view: AP wrist or knee
- Earliest X-ray sign: Widening of growth plate + cupping/fraying of metaphysis
- Earliest sign of radiological healing: Line of provisional calcification (LPC) at 2–4 weeks
- Gold standard for Vit D status: Serum 25(OH)D (Calcidiol)
- Most consistently raised parameter in active rickets: ALP (elevated in all forms)
- Harrison's sulcus: Horizontal groove at lower chest → diaphragm pulling soft ribs inward
- Rachitic vs Scurvy rosary: Rickets = soft, non-tender; Scurvy = hard, very tender
- Genu varum: Measured by intercondylar distance; genu valgum by intermalleolar distance
- Stoss therapy dose: 100,000–600,000 IU Vit D single oral dose
- Hungry bone syndrome: Worsening hypocalcemia when Vit D started without calcium → give calcium simultaneously
- Hypocalcemic seizure Rx: IV calcium gluconate 10% (0.5 mL/kg) slowly — NOT antiepileptics first
- VDDR Type I: CYP27B1 mutation → no 1,25(OH)₂D → treat with Calcitriol
- VDDR Type II: VDR mutation → resistance → high Calcitriol + alopecia totalis
- XLH: PHEX mutation → FGF23 excess → renal PO₄ wasting → NO hypocalcemia; treat with oral phosphate + calcitriol; now Burosumab (anti-FGF23)
- Hypophosphatasia: Very LOW ALP + rickets-like X-ray = key differentiator; treat with Asfotase alfa
- IAP recommendation: 400 IU/day Vit D from 1st week of life for all infants until 1 year
- Surgery in rickets: Only after biochemical and radiological healing confirmed; corrective osteotomy or hemiepiphysiodesis
- VDDR II clue: Alopecia totalis + very high 1,25(OH)₂D + poor response to calcitriol
🧮 Useful Formulas & Normal Values
- Vitamin D sufficiency: 25(OH)D ≥ 30 ng/mL; deficiency < 20 ng/mL
- Intercondylar distance (normal): ≤ 3 cm beyond 2 years (varum)
- Intermalleolar distance (normal): ≤ 8 cm beyond 7 years (valgum)
- Fontanelle closure: Anterior by 18 months
- Ca gluconate 10%: 0.5 mL/kg IV slow for hypocalcemic emergency
- Elemental calcium content: Calcium carbonate 40%; Calcium gluconate 9%; Calcium citrate 21%