Msk Dermatology · Year 2 · from Msk Dermatology

Case 2: Osteogenesis Imperfecta Type I

Patient Presentation

Demographics: 8-year-old boy

Chief Complaint: "He broke his arm again playing on the playground."

History of Present Illness: The patient's mother brings him to the emergency department after he fell off playground equipment from a height of approximately 2 feet and is now holding his left arm. This is his fourth fracture in 3 years (previous fractures: right radius age 5, left clavicle age 6, right tibia age 7).

Past Medical History:

• Multiple fractures as noted
• Premature loss of deciduous teeth
• Otherwise healthy

Family History:

• Father has history of multiple fractures and wears hearing aids
• Paternal grandmother had "brittle bones"

Physical Examination

• General: Alert child in mild distress, holding left arm
• Eyes: Blue sclerae noted bilaterally
• Teeth: Slightly opalescent appearance (dentinogenesis imperfecta)
• Left upper extremity: Swelling and tenderness of distal forearm, deformity present
• Musculoskeletal: Mild joint hypermobility, no current joint effusions
• Skin: Multiple well-healed scars from previous injuries

Workup and Results

Laboratory Studies:

Imaging:

• Left forearm X-ray: Distal radius fracture with mild osteopenia, thin cortices
• DXA (Z-score): Lumbar spine Z-score -2.5

Genetic Testing:

• COL1A1 mutation confirmed

Clinical Image

Blue sclerae, a characteristic finding in osteogenesis imperfecta due to thin scleral collagen allowing visualization of the underlying choroid. Source: Wikimedia Commons, CC BY-SA 3.0.

Diagnosis

Osteogenesis Imperfecta Type I (Mild Form)

Supporting Features:

• Recurrent low-trauma fractures
• Blue sclerae
• Dentinogenesis imperfecta
• Family history consistent with autosomal dominant inheritance
• COL1A1 mutation (type I collagen defect)
• Father with similar features

Treatment Plan

Acute Management:

1. Closed reduction of distal radius fracture
2. Short arm cast for 6 weeks

Long-term Management:

1. Bisphosphonate therapy: IV pamidronate every 4 months

• Increases bone density and reduces fracture rate

1. Calcium and Vitamin D: Ensure adequate intake
2. Physical therapy: Low-impact strengthening exercises
3. Occupational therapy: Activity modification education
4. Dental care: Regular follow-up with pediatric dentist
5. Audiology: Baseline hearing test with annual monitoring

Genetic Counseling:

• Autosomal dominant inheritance pattern
• 50% chance of transmission to offspring
• Family screening recommended

Teaching Points

1. Type I collagen defect: Osteogenesis imperfecta results from mutations in COL1A1 or COL1A2 genes encoding type I collagen, the predominant collagen in bone, skin, tendon, and sclera
2. Blue sclerae mechanism: Thin scleral collagen allows the bluish color of the underlying choroidal vessels to show through
3. OI classification: Type I is the mildest form with near-normal stature; more severe forms (Types II-IV) have progressive deformity and shorter stature
4. Bisphosphonates in pediatric bone disease: Reduce fracture rates and improve bone density but do not correct the underlying collagen defect

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