Rickets in Pediatrics: Clinical Case and Viva Questions
Clinical Case of Rickets
A 2-year-old boy is brought to the pediatric clinic by his parents with concerns about his delayed walking and bowed legs. The child was born full-term and exclusively breastfed until 12 months of age. His diet consists mainly of cereals and vegetables, with limited exposure to sunlight due to living in a northern climate.
On physical examination:
- Height and weight below the 3rd percentile for age
- Frontal bossing and delayed fontanelle closure
- Rachitic rosary (enlargement of the costochondral junctions)
- Widening of wrists and ankles
- Genu varum (bowed legs)
Laboratory findings:
- Serum calcium: 8.2 mg/dL (low normal)
- Serum phosphorus: 2.8 mg/dL (low)
- Alkaline phosphatase: 750 IU/L (elevated)
- 25-hydroxyvitamin D: 8 ng/mL (deficient)
- Parathyroid hormone: 85 pg/mL (elevated)
X-rays of the wrists and knees show cupping and fraying of the metaphyses, widening of the growth plates, and decreased bone density.
Based on the clinical presentation, laboratory findings, and radiographic evidence, the diagnosis of nutritional rickets due to vitamin D deficiency is made.
Varieties of Clinical Presentations of Rickets in Children
- Classical Nutritional Rickets:
- Bowed legs (genu varum) or knock knees (genu valgum)
- Delayed walking or waddling gait
- Frontal bossing and delayed fontanelle closure
- Rachitic rosary (enlarged costochondral junctions)
- Widening of wrists and ankles
- Hypocalcemic Presentation:
- Seizures or tetany, especially in infants
- Muscle cramps
- Laryngospasm or stridor
- Irritability or lethargy
- Growth and Developmental Delays:
- Short stature
- Delayed motor milestones
- Poor weight gain
- Delayed dentition
- Respiratory Manifestations:
- Recurrent respiratory infections
- Harrison's groove (horizontal indentation of lower chest)
- Pigeon chest deformity
- Adolescent Rickets:
- Diffuse bone pain, especially in weight-bearing joints
- Muscle weakness
- Difficulty climbing stairs or rising from a seated position
- Renal Rickets:
- Features of chronic kidney disease (pallor, hypertension)
- Growth retardation more severe than in nutritional rickets
- Bone deformities similar to nutritional rickets
- Hypophosphatemic Rickets:
- Lower limb deformities without significant muscle weakness
- Dental abscesses and enamel defects
- Normal or mildly short stature
- Vitamin D-Dependent Rickets Type 1:
- Early-onset rickets (within the first year of life)
- Severe hypocalcemia and associated symptoms
- Classical rickets features
Viva Questions and Answers Related to Rickets in Children
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Q: What is the primary cause of nutritional rickets?
A: The primary cause of nutritional rickets is vitamin D deficiency. This can result from inadequate dietary intake, insufficient sunlight exposure, or impaired vitamin D metabolism.
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Q: How does vitamin D deficiency lead to the skeletal manifestations of rickets?
A: Vitamin D deficiency leads to decreased calcium absorption in the intestines. This triggers increased parathyroid hormone (PTH) secretion, which increases calcium resorption from bones and phosphate excretion in urine. The resulting hypophosphatemia and inadequate calcium-phosphate product impair bone mineralization, leading to the skeletal manifestations of rickets.
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Q: What are the classic radiographic findings in rickets?
A: Classic radiographic findings include:
- Cupping and fraying of the metaphyses
- Widening of the growth plates
- Decreased bone density (osteopenia)
- Bowing of long bones
- Coarse trabecular pattern
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Q: What are the key laboratory findings in nutritional rickets?
A: Key laboratory findings include:
- Low or low-normal serum calcium
- Low serum phosphorus
- Elevated alkaline phosphatase
- Low 25-hydroxyvitamin D levels
- Elevated parathyroid hormone (PTH)
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Q: How do you distinguish between calcium-deficiency and vitamin D-deficiency rickets?
A: While both can present with similar skeletal manifestations, calcium-deficiency rickets typically shows normal 25-hydroxyvitamin D levels and more severe hypocalcemia. Vitamin D-deficiency rickets shows low 25-hydroxyvitamin D levels and may have less severe hypocalcemia due to secondary hyperparathyroidism.
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Q: What are the main risk factors for developing nutritional rickets?
A: Main risk factors include:
- Exclusive breastfeeding without vitamin D supplementation
- Dark skin pigmentation
- Limited sunlight exposure
- Malabsorption disorders
- Vegan or vegetarian diets without supplementation
- Obesity
- Certain medications (e.g., anticonvulsants)
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Q: How does the clinical presentation of rickets differ between infants and older children?
A: In infants, rickets may present with hypocalcemic seizures, craniotabes (soft skull bones), and delayed fontanelle closure. Older children more commonly present with bowed legs, knocked knees, widened wrists, and gait abnormalities.
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Q: What is the recommended treatment for nutritional rickets?
A: Treatment involves high-dose vitamin D supplementation (typically 2000-6000 IU/day or 50,000 IU weekly for 6-12 weeks) followed by a maintenance dose. Calcium supplementation is also crucial, especially in calcium-deficiency rickets. Addressing underlying causes and providing nutritional counseling are essential.
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Q: How long does it typically take to see clinical improvement after starting treatment?
A: Biochemical improvements are often seen within days to weeks. Radiographic improvements may be evident in 2-3 months. Clinical improvements in bone deformities can take several months to years, with better outcomes in younger children.
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Q: What is hypophosphatemic rickets, and how does it differ from nutritional rickets?
A: Hypophosphatemic rickets is a group of genetic disorders characterized by renal phosphate wasting. Unlike nutritional rickets, it presents with normal or elevated 1,25-dihydroxyvitamin D levels, normal calcium levels, and does not respond to vitamin D supplementation alone. Treatment typically involves phosphate supplementation and calcitriol.
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Q: What are the potential long-term consequences of untreated rickets?
A: Potential long-term consequences include:
- Permanent bone deformities
- Short stature
- Dental abnormalities
- Increased risk of fractures
- Chronic pain
- Impaired motor development
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Q: How does vitamin D-dependent rickets type 1 (VDDR1) differ from nutritional rickets?
A: VDDR1 is a rare autosomal recessive disorder caused by a defect in the 1α-hydroxylase enzyme, which converts 25-hydroxyvitamin D to the active form 1,25-dihydroxyvitamin D. Unlike nutritional rickets, VDDR1 does not respond to standard vitamin D supplementation and requires lifelong treatment with calcitriol.
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Q: What is the role of parathyroid hormone (PTH) in the pathophysiology of rickets?
A: In rickets, low calcium levels stimulate PTH secretion. PTH increases calcium resorption from bone and promotes calcium reabsorption in the kidneys. It also increases phosphate excretion in urine, contributing to hypophosphatemia. The elevated PTH levels help maintain serum calcium but at the expense of bone mineralization.
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Q: How does renal rickets differ from other forms of rickets?
A: Renal rickets occurs in chronic kidney disease due to impaired 1α-hydroxylation of vitamin D and phosphate retention. It's characterized by more severe growth retardation, features of chronic kidney disease (e.g., anemia, hypertension), and often requires more complex management including phosphate binders and active vitamin D analogs.
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Q: What is the significance of alkaline phosphatase levels in rickets?
A: Elevated alkaline phosphatase is a sensitive marker for rickets, reflecting increased osteoblastic activity. It's often the first biochemical abnormality to appear and the last to normalize with treatment, making it useful for both diagnosis and monitoring treatment response.
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Q: How do you prevent rickets in high-risk populations?
A: Prevention strategies include:
- Universal vitamin D supplementation for breastfed infants (400 IU/day)
- Vitamin D fortification of foods
- Encouraging safe sun exposure
- Nutritional education
- Screening and supplementation for at-risk pregnant women
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Q: What is the relationship between calcium and vitamin D in the context of rickets?
A: Vitamin D is crucial for calcium absorption in the intestines. In vitamin D deficiency, calcium absorption is impaired, leading to hypocalcemia. However, calcium deficiency alone can also cause rickets, even with adequate vitamin D levels. Both nutrients are essential for proper bone mineralization.
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Q: How does rickets affect the growth plate, and what are the consequences?
A: In rickets, the growth plate becomes disorganized and widened due to impaired mineralization. This leads to the characteristic cupping and fraying seen on X-rays. The weakened growth plate is prone to deformities under mechanical stress, resulting in bowed legs or knock knees.
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Q: What is the "rachitic rosary," and why does it occur?
A: The rachitic rosary refers to the enlargement of the costochondral junctions, creating bead-like prominences along the rib cage. It occurs due to excessive unmineralized osteoid formation at these junctions as the body attempts to compensate for the weakened bone structure.
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Q: How does nutritional rickets impact the immune system?
A: Vitamin D plays a crucial role in immune function. Rickets can lead to increased susceptibility to infections, particularly respiratory infections. This is due to vitamin D's role in enhancing innate immunity and regulating inflammatory responses.
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Q: What are the indications for surgical intervention in rickets?
A: Surgical intervention is generally reserved for severe or persistent deformities that don't correct with medical management and growth. Indications may include:
- Severe bowing of legs affecting gait (usually after 6-8 years of age)
- Progressive deformities despite adequate medical treatment
- Deformities causing functional impairment
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Q: How does vitamin D toxicity present, and how is it managed?
A: Vitamin D toxicity, though rare, can occur with excessive supplementation. Symptoms include hypercalcemia (nausea, vomiting, confusion, polyuria), nephrocalcinosis, and soft tissue calcifications. Management involves discontinuing vitamin D, reducing calcium intake, hydration, and in severe cases, corticosteroids or bisphosphonates.
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Q: What is the role of fibroblast growth factor 23 (FGF23) in phosphate metabolism and its relevance to certain forms of rickets?
A: FGF23 is a hormone produced by osteocytes that plays a crucial role in phosphate homeostasis. It acts on the kidneys to increase phosphate excretion and decrease 1α-hydroxylase activity, thereby reducing 1,25-dihydroxyvitamin D production. In X-linked hypophosphatemic rickets (XLH), mutations lead to excess FGF23 production, resulting in renal phosphate wasting and impaired vitamin D activation. This understanding has led to the development of FGF23 antibodies (e.g., burosumab) as a targeted therapy for XLH.
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Q: How does rickets affect dental development, and what are the long-term dental implications?
A: Rickets can significantly impact dental development, leading to:
- Delayed tooth eruption
- Enamel hypoplasia, increasing susceptibility to caries
- Dentinal defects
- Enlarged pulp chambers
- Increased risk of dental abscesses, particularly in hypophosphatemic rickets
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Q: What is the concept of vitamin D resistance, and how does it relate to certain types of rickets?
A: Vitamin D resistance refers to conditions where normal vitamin D metabolism is impaired due to genetic defects, leading to rickets despite normal or even elevated vitamin D levels. Two main types are:
- Vitamin D-dependent rickets type 2 (VDDR2): Caused by mutations in the vitamin D receptor gene, resulting in end-organ insensitivity to 1,25-dihydroxyvitamin D.
- Hereditary vitamin D-resistant rickets (HVDRR): A severe form of VDDR2, often associated with alopecia.
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Q: How does rickets in premature infants differ from rickets in full-term infants?
A: Rickets in premature infants, often called osteopenia of prematurity, differs in several ways:
- Etiology: Often multifactorial, including inadequate calcium and phosphate intake, immature gut absorption, and limited vitamin D stores.
- Timing: Can occur earlier, often within the first few months of life.
- Presentation: May be subclinical, often detected on routine screening or incidentally on chest X-rays.
- Management: Requires careful nutritional management, often with higher calcium and phosphate supplementation in addition to vitamin D.
- Long-term outcomes: Can impact long-term bone health and growth if not adequately addressed.
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Q: What are the current global initiatives to combat rickets, and how effective have they been?
A: Global initiatives to combat rickets include:
- Universal vitamin D supplementation programs for infants
- Food fortification policies (e.g., vitamin D-fortified milk)
- Public health education on the importance of vitamin D and calcium
- Integration of rickets prevention into maternal and child health programs
- Global consensus recommendations on prevention and management of nutritional rickets
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Q: How does the management of vitamin D-dependent rickets differ from nutritional rickets?
A: Management of vitamin D-dependent rickets differs in several key aspects:
- VDDR Type 1 (1α-hydroxylase deficiency):
- Requires lifelong treatment with calcitriol (1,25-dihydroxyvitamin D)
- Standard vitamin D supplements are ineffective
- Calcium supplementation is often necessary
- VDDR Type 2 (Vitamin D receptor defects):
- May require very high doses of calcitriol
- Often needs high-dose calcium supplementation, sometimes intravenously
- In severe cases, may not respond to oral therapy and require long-term intravenous calcium
- VDDR Type 1 (1α-hydroxylase deficiency):
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Q: What are the potential neurological manifestations of rickets, and what is their pathophysiology?
A: Neurological manifestations of rickets can include:
- Hypocalcemic seizures: Due to low serum calcium levels affecting neuronal excitability
- Tetany: Caused by low ionized calcium, leading to increased neuromuscular excitability
- Developmental delays: Potentially due to the role of vitamin D in brain development and function
- Intracranial hypertension: Rarely reported, possibly due to vitamin A metabolism interactions
- Myopathy: Resulting from vitamin D deficiency affecting muscle function
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Q: How does rickets impact growth hormone axis and overall endocrine function?
A: Rickets can impact the growth hormone (GH) axis and endocrine function in several ways:
- Growth hormone resistance: Chronic vitamin D deficiency may lead to decreased sensitivity to GH
- Reduced IGF-1 levels: Potentially due to impaired liver production in the setting of vitamin D deficiency
- Delayed puberty: Severe, prolonged rickets can affect the timing of puberty
- Parathyroid hyperplasia: Secondary to chronic calcium deficiency
- Potential impact on thyroid function: Some studies suggest an association between vitamin D deficiency and thyroid disorders
