Diagnosing Rickets: Distinguishing the Causes

Rickets is a condition in which growing bones fail to mineralize properly, leading to soft, weak bones and characteristic skeletal changes. In most cases, it’s due to vitamin D, calcium or phosphate deficiencies. Understanding how is rickets diagnosed involves combining clinical assessment, laboratory tests and imaging studies. Early recognition and treatment can help prevent long-term complications.

Typical Signs and Symptoms

Children and adolescents with rickets often show:

• Delayed growth or short stature
• Bone pain or tenderness, especially in the legs
• Bowed legs (genu varum) or knock-knees (genu valgum)
• Swollen wrists and ankles (due to widened growth plates)
• Dental problems (delayed tooth eruption, enamel defects)
• Muscle weakness or delayed motor milestones

Infants may have craniotabes (soft skull bones) or delayed closure of fontanelles. Adults with residual or late-onset rickets can present with bone pain, muscle weakness and fractures.

Key Risk Factors

Identifying risk factors helps guide the diagnostic workup:

• Limited sunlight exposure (darker skin, indoor lifestyle, high latitude)
• Exclusive breastfeeding beyond 6 months without supplementation
• Malabsorption (celiac disease, cystic fibrosis, inflammatory bowel disease)
• Chronic kidney disease or liver disorders
• Certain medications (anticonvulsants, glucocorticoids)
• Genetic conditions affecting vitamin D or phosphate handling

How Is Rickets Diagnosed: The Diagnostic Process

Diagnosing rickets involves a stepwise approach:

1. Detailed medical history
2. Physical examination
3. Laboratory testing
4. Imaging studies
5. Specialized tests (when needed)

1. Medical History and Physical Exam

Your doctor will ask about:

• Dietary habits (vitamin D, calcium intake)
• Sunlight exposure
• Family history of bone or mineral disorders
• Growth and developmental milestones
• Symptoms such as bone pain, muscle weakness or fractures

During the exam, the physician looks for:

• Bone deformities (bowing of the legs, rib “beading”)
• Widened, tender growth plates at wrists, ankles, ribs
• Dental abnormalities
• Muscle strength and tone

2. Laboratory Tests

Blood and urine tests help confirm the diagnosis and identify the underlying cause:

• Serum 25-hydroxyvitamin D (25[OH]D)
– Deficiency: <20 ng/mL (50 nmol/L)
– Insufficiency: 20–30 ng/mL (50–75 nmol/L)

• Serum calcium and phosphate
– Low or low-normal levels suggest nutritional or malabsorptive rickets

• Alkaline phosphatase (ALP)
– Elevated in active rickets as bone turnover increases

• Parathyroid hormone (PTH)
– Secondary hyperparathyroidism often accompanies vitamin D deficiency

• 1,25-dihydroxyvitamin D (calcitriol)
– Usually low or normal in nutritional rickets; elevated in vitamin D–resistant forms

• Urinary calcium and phosphate
– Helps distinguish renal phosphate losses from dietary deficiency

3. Imaging Studies

Radiographs (X-rays) of the wrists, knees or long bones reveal classic signs:

• Metaphyseal cupping (funneling at the growth plate)
• Fraying or splaying of metaphyses
• Widened growth plates
• Bowing deformities in long bones

In mild cases, changes may be subtle. Imaging helps assess severity and monitor response to treatment.

4. Specialized Tests

If basic labs and X-rays do not clearly identify the cause, further evaluation may include:

• Genetic testing for forms of hereditary rickets (e.g., X-linked hypophosphatemia)
• Renal ultrasound or function tests for kidney-related phosphate wasting
• Bone biopsy (rarely needed) to assess mineralization directly

Distinguishing the Underlying Causes

Once rickets is confirmed, pinpointing the cause is crucial:

1. Nutritional Rickets

   • The most common form.
   • Low 25(OH)D, low calcium, high PTH, high ALP.
   • Improves with vitamin D and calcium supplementation.

2. Vitamin D–Resistant Rickets

   • Genetic defects in vitamin D receptor or activation.
   • Normal or high 25(OH)D, elevated 1,25(OH)₂D.
   • Requires active vitamin D analogs (calcitriol).

3. Hypophosphatemic Rickets

   • Often X-linked, due to excess fibroblast growth factor 23 (FGF23).
   • Low phosphate, normal calcium, normal 25(OH)D, elevated ALP.
   • Treated with phosphate supplements and sometimes growth hormone.

4. Renal Rickets (Renal Osteodystrophy)

   • Chronic kidney disease causes phosphate retention and low calcitriol.
   • Abnormal PTH, calcium and phosphate patterns.
   • Managed with phosphate binders and active vitamin D.

5. Drug-Induced Rickets

   • Anticonvulsants can accelerate vitamin D breakdown.
   • Glucocorticoids impair bone formation.
   • Adjusting medications and supplementing nutrients often helps.

Differential Diagnosis

Other conditions may mimic rickets:

• Scurvy (vitamin C deficiency): Corkscrew hairs, gum disease
• Hypophosphatasia: Low alkaline phosphatase, premature tooth loss
• Juvenile osteoporosis or osteogenesis imperfecta: Fractures, blue sclera
• Metabolic bone diseases (e.g., renal tubular acidosis)

A thorough workup helps avoid misdiagnosis.

Management Overview

Treatment varies by cause but generally includes:

• Vitamin D supplementation (ergocalciferol or cholecalciferol)
• Adequate dietary calcium (milk, fortified foods, supplements)
• Phosphate supplements for phosphate-wasting forms
• Active vitamin D analogs (for resistant or renal cases)
• Monitoring growth, labs and X-rays every 3–6 months

Early intervention promotes normal bone development and prevents permanent deformities.

When to Seek Medical Advice

If you notice persistent bone pain, bowing of the legs, delayed growth or other concerning signs, it’s important to act:

• Consider a free, online symptom check, using the doctor approved Ubie Symptom Checker to guide your next steps.
• Discuss any worries or abnormal findings with your pediatrician or family doctor.
• Urgent warning signs (high fever, severe pain, inability to walk) warrant immediate medical attention.

Always speak to a doctor about anything that could be life threatening or serious. Proper evaluation and timely treatment can make a significant difference in outcomes.

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References for this overview include guidelines from the American Academy of Pediatrics, Endocrine Society, and peer-reviewed pediatric and endocrinology journals. By following a structured diagnostic approach, healthcare providers can accurately answer the question how is rickets diagnosed, distinguish among its causes, and tailor treatment to each child’s needs.