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Kabuki syndrome is caused by a mutation in the KMT2D gene or the KDM6A gene, whereas, in some cases, the cause remains unknown.
Most cases (between 55 and 80 percent) of Kabuki syndrome are caused by mutations in the KMT2D gene that is inherited in an autosomal dominant pattern. This means a mutation in only one copy of the KMT2D gene in each cell is sufficient to cause the features of this condition.
Some cases are caused by mutations in the KDM6A gene, which is inherited in an X-linked dominant manner. Similar to a mutation in the KMT2D gene, only one mutated copy of the KDM6A gene, located on the X chromosome, is enough to cause the disorder.
Because females have two X chromosomes and males have one X chromosome and one Y chromosome, X-linked dominant conditions affect males and females differently and their respective children.
- If the male has the mutated X-linked gene
- All his female children will inherit the mutated gene (because they receive his X chromosome)
- None of his male children will inherit the mutated gene (because they inherit only the Y chromosome)
- If the female has the mutated X-linked gene
- Each of her children (both male and female) has a 50 percent chance to inherit the mutated gene
What is kabuki syndrome?
Kabuki syndrome is a rare, genetic, and congenital (present since birth) disorder, affecting multiple parts of the body and characterized by a characteristic facial appearance, skeletal abnormalities, short stature, heart defects, and intellectual disability.
Kabuki syndrome was originally called Kabuki-makeup syndrome and was first reported in 1981 by Japanese physicians Norio Niikawa and Yoshikazu Kuroki.
- It is also called:
- Kabuki makeup syndrome
- Niikawa-Kuroki syndrome
15 characteristic facial features of kabuki syndrome
- Arched eyebrows
- Wide eyes that often slant upward
- Long and thick eyelashes
- Long palpebral fissures (abnormally long openings between the eyelids)
- A blue tint to the whites of the eyes (blue sclera)
- Prominent ears
- Ptosis (drooping of the upper eyelid)
- Strabismus (misaligned eyes)
- Micrognathia (abnormally small jaw)
- Downward slanting corners of the mouth
- A depressed tip of the nose
- Cleft lip
- A highly arched or cleft palate
- Widely spaced, irregular teeth
- Short stature
What causes kabuki syndrome?
Most often (up to 80 percent of cases), kabuki syndrome is caused by a mutation in the KMT2D gene or the KDM6A gene, whereas, in some cases, the cause remains unknown.
- The KMT2D gene and KDM6A gene are responsible for the production of an enzyme called lysine-specific methyltransferase 2D, which is present in many parts of the body.
- This enzyme modifies proteins called histones, which attach to the DNA and provides chromosomes with their shape.
- By a process called methylation (addition of a methyl group to histones), this enzyme helps control the activity of certain genes that activates those genes that are important for development.
Mutations in either of the two genes may lead to the absence of the related enzyme, disrupting the histone methylation, thus resulting in impairing the activation of certain genes needed for normal development.
15 symptoms of kabuki syndrome
Some features of Kabuki syndrome may be present at birth, whereas other features become apparent as affected children age.
Specific symptoms and severity vary with people and may include:
- Seizures
- Microcephaly (a small head size)
- Hypotonia (weak muscle tone)
- Eye or vision problems
- Hearing problems
- Cleft palate
- Dental problems, such as missing, misaligned, or misshapen teeth
- Mild to moderate intellectual disability
- Small and thin fingernails and toenails
- Speech and language delay
- Congenital heart defects
- Skeletal abnormalities, such as abnormally short fingers and toes (brachydactyly), curved pinky finger (clinodactyly), flat feet, loose joints, vertebrae abnormalities, cranial malformations, spine abnormalities (such as abnormal curvature of the spine: scoliosis or kyphosis), and joint dislocations
- Feeding difficulties include gastroesophageal reflux, poor sucking ability, and difficulty absorbing or digesting nutrients from food (malabsorption)
- Failure to thrive
- Susceptible to recurring infections including upper respiratory infections, pneumonia, and recurrent ear infections (otitis media)
How is kabuki syndrome diagnosed?
Healthcare professionals look for distinctive facial features, persistent fingertip pads, low muscle tone, developmental delay, and intellectual disability. Medical history, blood tests, and chromosomal studies could be used to confirm the diagnosis and rule out other disorders.
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What is the life expectancy with kabuki syndrome?
Life expectancy is not shortened in most cases of Kabuki syndrome, particularly if congenital anomalies, such as congenital heart defects and infections, are properly managed during childhood.
Some cases have coexisting conditions, which may shorten life expectancies, such as hypoplastic left heart syndrome, kidney dysfunction, and immunologic complications.
10 complications of kabuki syndrome
- Congenital heart defects
- Coarctation of the aorta (narrowing of the main artery of the body)
- Ventricular or atrial septal defects (holes in the membranes that separate the chambers of the heart)
- Renal abnormalities include malformation or underdevelopment of the kidneys (renal dysplasia or hypoplasia)
- Hydronephrosis (obstruction of the normal flow of the urine from the kidneys)
- Horseshoe kidneys (fusion of the kidneys at the base forming a horseshoe shape)
- Gastrointestinal abnormalities include malrotation of the colon and absence or blockage of the anal opening (anal atresia)
- Immunological deficiencies and a higher risk of developing autoimmune disorders
- Premature thelarche (early onset of breast development) in females
- Cryptorchidism (undescended testicles) in males
How is kabuki syndrome treated?
There is no specific cure available for kabuki syndrome, treatment is focused on the specific signs and symptoms of each affected person.
Early intervention may be beneficial to the affected children, including special remedial education, sensory integration therapy, physical and occupational therapy, and speech therapy.
Children who experience severe feeding difficulties may require the placement of a gastrostomy tube. Additional complications, such as hip dislocation, scoliosis, cardiac defects, and cleft palate, may need surgical treatment.
