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Understanding the Patient with Fragile X Syndrome

To successfully provide oral health care to this special needs population, dental hygienists must be aware of the distinct characteristics of this syndrome.

Dental hygienists may feel inadequately prepared to provide oral care services to patients who have special care needs, including those who have intellectual impairments, due to a lack of instruction and experience in this area.1-4 Clinicians may be uncomfortable when patients present with unfamiliar conditions and behaviors. To provide efficacious care, dental professionals need to understand the characteristics and expected behaviors of patients who have special care needs. Fragile X syndrome (FXS) is one of the most common inherited causes of intellectual impairment,6-9 and it presents with specific characteristics that are important to note before beginning any type of dental treatment.

FXS is caused by a mutation in a single gene on the long arm of the X chromosome. The syndrome results from the presence of more than 200 trinucleotide (cytosine-guanineguanine or CGG) repeats within the fragile X mental retardation 1 gene, which leads to a deficient production of the fragile X mental retardation protein—a protein necessary for normal brain development. Normal alleles of the fragile X gene typically contain between five and 55 CGG repeats. Individuals with genes containing 55 to 200 repeats are fragile X premutation carriers but do not have the syndrome. Premutations are unstable and often expand to full mutation when transmitted by a carrier female. Although premutation carriers do not have FXS, they may have clinical disorders such as anxiety, attention deficit hyperactivity disorder, executive function deficits, mild cognitive deficits, premature ovarian failure, and adult onset tremor and ataxia.10,13-15

Although researchers are uncertain of the exact prevalence, males are affected twice as often and more severely than females. The genetic condition affects approximately one in every 4,000 males and one in every 8,000 females.7,9-12


Distinguishing characteristics may occur in individuals with FXS, but they are often subtle until adolescence. Characteristics of the head and neck may include prognathism, high-arched palate, cleft palate, prominent lateral palatine ridges, anterior and posterior crossbites, malocclusion, and increased occlusal attrition. A large head circumference and elongated face and ears are common.16 Many people with FXS have loose, flexible joints that dislocate easily. They may also have flat feet and their hands may appear large and fleshy. Many have the ability to extend joints like the thumb, knee, and elbow farther than normal. Eye problems due to muscle weakness are common. Mitral valve prolapse may be present. Macro orchidism (abnormally large testes) may appear in the post-pubertal male.16-18


Males with FXS generally have mental retardation, although only a small percentage of affected females present with mental retardation.19 The degree of mental disability may be difficult to assess when behaviors include hyperactivity, poor attention span, and impulsiveness; thus, children with FXS usually function higher than their IQs indicate.17 According to the Diagnostic and Statistical Manual, a score between 85 and 115 on an IQ test is considered average intelligence. Less than 20% of males with FXS have an IQ in the average range.20 Few people who have the syndrome are severely or profoundly impaired with IQs below 40 or 25, respectively.21 In general, those with a full mutation tend to have an IQ somewhere between 40 and 85, which is considered mild to moderate mental impairment.22

Females who have FXS are more likely to have relatively normal cognitive development. They may experience difficulties in learning, which typically appear when their academic achievement in some areas is lower.

Because intelligence is influenced by many factors, individuals with FXS have areas of strength and weakness. They tend to have good memories for picture and visual patterns that help them learn to recognize letters and words and to follow instructions that are presented as pictures. Abstract ideas, organizing information, planning ahead, and solving problems are typically problematic for those who have FXS.23


Typically, males who have FXS experience moderate to severe delays in communication with expressive language being affected more than receptive language. Characteristic speech may be hurried with unusual rhythm, which presents as stuttered or repetitive sentences.18,22 An inability to pronounce multisyllabic words causes parts of words to be omitted from sentences, resulting in speech that is difficult to understand.17 In addition to the challenge of expressive language, failure to recognize and understand nonverbal cues creates further language barriers for individuals with FXS. Communication transmitted through voice tone and body language may be ignored or misinterpreted, causing a breakdown in communication.23


Many children who have FXS display hypersensitive reactions to stimuli such as bright lights, loud noises, and touch. Making eye contact may be problematic. When these sensory systems are overloaded, aberrant behaviors frequently result.23

Social situations are often challenging for those with FXS. New situations may provoke fear and anxiety that result in shyness, aggression, or tantrums. Unexpected changes in routine can elicit negative responses including self-injurious behaviors and repetitive actions such as biting and hand flapping. Some children respond by becoming extremely distracted, rigid, or tense while others verbally protest or cry. Adolescent changes and increased hormone levels tend to increase aggression in males during this time period.21,23 In general, complying with social norms can challenge individuals with FXS as overstimulation is likely to result in hyperactivity, distractibility, and impulsive behaviors.18


FXS is the most commonly known genetic syndrome associated with autism spectrum disorder (ASD).10 Approximately 4% of individuals with an ASD also have FXS, whereas an estimated 5% to 60% of individuals with FXS also have an ASD diagnosis.24,25 The wide variation in the ASD prevalence among those with FXS is likely due to variation in measures used. Unlike FXS the diagnosis for ASD is entirely behavioral and has no biomarkers. At this time, the known association between FXS and ASD occurs in the social/emotional domain. Overlapping behaviors include communication deficits, social withdrawal, avoidant eye gaze, and repetitive behaviors.10,24,25

Developing an effective approach to communication is paramount when providing oral care for individuals with FXS. Parents or other individuals who are familiar with the patient can provide valuable insight into effective communication strategies. Visual aids should be used to present concrete examples of ideas and concepts. Laminated photos can be created and used as picture prompts to illustrate each procedure to the patient. The success of the dental visit hinges on the patient’s understanding of what is expected and his or her ability and willingness to perform the behaviors expected. Ample time should be provided to allow the patient to become familiar with the environment and planned procedures. Undesirable patient behavior, resulting from exposure to excess stimuli or long appointments, can be avoided with preventive planning. Multiple short appointments may be necessary to gradually introduce the patient to the dental environment.


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From Dimensions of Dental Hygiene. June 2009; 7(6): 22, 24-25.

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