Fragile X Syndrome Medical Issues: Birth to Adolescence

Infants & Toddlers

Most infants with Fragile x syndrome (FXS) are healthy and don’t require extensive medical intervention. However there are some common medical conditions that can occur more often in babies with Fragile X syndrome.

Birth Defects

Babies with FXS have an increased chance of some congenital abnormalities such cleft lip, cleft palate, clubfoot, congenital hip dislocation, and hernias, perhaps all related to loose connective tissue. These are all common birth defects among children without FXS as well, therefore babies with these conditions are not routinely tested for FXS unless there is some other indication, such as developmental delay or a family history of FXS.

Low Muscle Tone

Many babies with FXS have hypotonia, aka low muscle tone. This is sometimes referred to as being “floppy,” which for a baby can cause difficulty in holding up their head, also known as “head lag.”

Because low muscle tone affects gross motor skills, such as sitting up or rolling over, hypotonia can contribute to the developmental delays often seen in babies and toddlers with FXS.

Digestive Disorders

Although many babies with FXS do well in the newborn period, others have difficulty with feeding, vomiting, and/or gastroesophageal reflux (GER). This may be related to connective tissue abnormalities, low muscle tone (hypotonia), dysfunction of the gastroesophageal sphincter, or a hypersensitive gag reflex.

Some parents report that vomiting in babies with GER can be resolved by positioning them upright after meals or feeding them thicker baby food. Occasionally, medication is needed to decrease reflux.

Babies will sometimes be diagnosed with what is called “failure to thrive.” This is typically related to difficulties in sucking, GER, or an aversion to food textures. If feeding difficulties are a problem, particularly sucking or intolerance of certain food textures, consultation with an occupational and/or speech and language therapist, or therapies such as oral desensitization, oral stimulation, and oral motor coordination, can be helpful.

Ear & Sinus Infections

Beginning in the first year of life, frequent otitis media (middle ear infections) are a problem for many boys (and some girls) with FXS. In fact, often the speech and language delays seen in children with FXS are mistakenly attributed to chronic ear infections, sometimes delaying the FXS diagnosis.

This problem requires treatment to avoid a hearing loss that may further compromise language development. If a conductive hearing loss persists after acute antibiotic treatment, ear tubes (most commonly referred to as PE—pressure equalizing—tubes, but also known as tympanostomy or ventilating tubes) are often recommended.

Recurrent sinusitis is also a common problem in FXS, which may be related to the facial structure or the connective tissue problems that lead to recurrent ear infections.

Children and Adolescents

Urinary Tract Infections

Some children (more often boys), with FXS, may have an increased susceptibility to urinary tract infections and reflux (the backing up of urine into the urethra and bladder). The pediatrician may suspect an infection if the child has a fever of unknown origin with no other explanation, and thus a urine sample will be obtained.


Approximately 20% of males and a smaller percentage of females with FXS have epilepsy. If your physician suspects your child is having seizures, often an EEG (electroencephalogram, which detects electrical activity in the brain) is performed. If seizures are confirmed, seizure medication is usually prescribed.

Eye Disorders

Children with FXS have an increased susceptibility for vision and eye disorders, which are common in childhood.

These include:

  • Strabismus: Also called “lazy eye,” this condition causes the eye to appear “crossed” or drifting to the middle. This is often due to low muscle tone in the eye, a symptom of the hypotonia present in many babies or children with FXS.
  • Ptosis: Drooping of the eyelid, again often related to low muscle tone.
  • Nystagmus: Shaking of the iris in a back and forth motion.
  • Myopia/Hyperopia: Subtle near- or farsightedness.

It is recommended that all children with FXS be referred to an ophthalmologist if the pediatrician suspects any of these common eye or vision conditions.

Connective Tissue Issues

Connective tissue is the tissue that holds together the body such as skin, muscles, tendons, cartilage, ligaments, bones, and blood vessels. Many individuals with FXS have differences in their connective tissue. Some of these connective tissue problems include:

  • Scoliosis: Curvature of the spine, usually not severe.
  • Flat feet: Also called pes planus.
  • Hernias: Inguinal (i.e., groin) hernias.
  • Cardiac murmur: Often a functional or innocent murmur, it is sometimes indicative of mitral valve prolapse (or MVP, which is improper closure of the valve between the heart’s upper and lower left chambers.). Occasionally an evaluation by a cardiologist is warranted to confirm MVP, and if confirmed, the cardiologist may recommend antibiotics prior to dental procedures or surgery.
  • Hyperflexible joints: Particularly of the wrists, fingers, and elbows.
  • Soft skin
  • Macroorchidism: Testicular volume normally increases during the early stages of puberty, but in boys with FXS this increase is usually quite dramatic, leading to macroorchidism (i.e., enlarged testicles). These changes are typical for FXS, and do not require intervention. Some boys with FXS develop large testicles prior to the onset of puberty.