Fragile X syndrome

Overview

Board takeaway: Use predictable visits and sensory adaptations; review seizures, medications, and actual cardiac disease before sedation or invasive care.

How does Fragile X syndrome affect dental management?

• Communication: Ask the patient and caregiver about communication, sensory triggers, and calming strategies; avoid forcing eye contact or inferring comprehension from gaze or speech
• Visit structure: Short, predictable visits, visual schedules, the same team, a quiet room, and gradual desensitization
• Seizures and medication: Review seizure control and medications (stimulants, SSRIs, antipsychotics, anticonvulsants)
• Cardiac review: Review aortic root dilation and mitral valve prolapse; mitral valve prolapse alone does not need endocarditis prophylaxis.
• Sedation decision: Escalate to sedation or GA after weighing cooperation, medical risk and treatment need

Exam pearl

What is Fragile X syndrome?

An FMR1-related genetic condition, usually caused by a CGG repeat expansion, associated with intellectual disability and variable behavioral and developmental differences.

What are the main systemic features of Fragile X syndrome?

• Genetics: the most common inherited cause of intellectual disability; FMR1 CGG repeat over 200 (full mutation), which silences the gene.
• Inheritance: X-linked; repeats can expand when passed through the mother.
• Males: generally more severely affected.
• Females: a full FMR1 mutation can also cause intellectual disability, learning difficulties, or behavioral features; do not describe all affected females as unaffected carriers.
• Premutation: a distinct genetic category.
• Appearance: long narrow face, prominent jaw and ears, macroorchidism after puberty, joint hyperlaxity, flat feet.
• Behavior: anxiety, gaze avoidance, hyperarousal, ADHD and autism features.
• Seizures: occur in some patients; more frequent in affected males.
• Cardiac: mitral valve prolapse and aortic root dilation in some.

What oral findings occur in Fragile X syndrome?

• High-arched palate, mandibular prognathism, crowding and malocclusion
• Bruxism and mouthing behavior
• Hygiene limited by tactile defensiveness and motor planning

Sources

• Supplemental study guide: Pediatric Dental Study Guide: Fragile X syndrome
• Management of Dental Patients with Special Health Care Needs
• Behavior Guidance for the Pediatric Dental Patient
• Supplemental genetics: MedlinePlus Genetics: fragile x syndrome
• AAPD best practice: AAPD: Antibiotic Prophylaxis for Dental Patients at Risk for Infection (2026)