DiGeorge syndrome (22q11.2 deletion syndrome)

Overview

DiGeorge syndrome, more accurately known by a broader term — 22q11.2 deletion syndrome — is a disorder caused when a small part of chromosome 22 is missing. This deletion results in the poor development of several body systems.

The term 22q11.2 deletion syndrome covers terms once thought to be separate conditions, including DiGeorge syndrome, velocardiofacial syndrome and other disorders that have the same genetic cause, though features may vary slightly.

Medical problems commonly associated with 22q11.2 deletion syndrome include heart defects, poor immune system function, a cleft palate, complications related to low levels of calcium in the blood, and delayed development with behavioral and emotional problems.

The number and severity of symptoms associated with 22q11.2 deletion syndrome vary. However, almost everyone with this syndrome needs treatment from specialists in a variety of fields.

Symptoms

Signs and symptoms of DiGeorge syndrome (22q11.2 deletion syndrome) can vary in type and severity, depending on what body systems are affected and how severe the defects are. Some signs and symptoms may be apparent at birth, but others may not appear until later in infancy or early childhood.

Signs and symptoms may include some combination of the following:

• Heart murmur and bluish skin due to poor circulation of oxygen-rich blood (cyanosis) as a result of a heart defect
• Frequent infections
• Certain facial features, such as an underdeveloped chin, low-set ears, wide-set eyes or a narrow groove in the upper lip
• A gap in the roof of the mouth (cleft palate) or other problems with the palate
• Delayed growth
• Difficulty feeding, failure to gain weight or gastrointestinal problems
• Breathing problems
• Poor muscle tone
• Delayed development, such as delays in rolling over, sitting up or other infant milestones
• Delayed speech development or nasal-sounding speech
• Learning delays or disabilities
• Behavior problems

When to see a doctor

Other conditions may cause signs and symptoms similar to 22q11.2 deletion syndrome. So it's important to get an accurate and prompt diagnosis if your child shows any signs or symptoms listed above.

Doctors may suspect 22q11.2 deletion syndrome:

• At birth. If certain conditions — a severe heart defect, cleft palate or a combination of other factors typical of 22q11.2 deletion syndrome — are readily apparent at birth, diagnostic tests will likely begin before your child leaves the hospital.
• At well-baby visits. Your family doctor or pediatrician may suspect the disorder because of a combination of illnesses or disorders that become apparent over time. Other issues may come to the attention of your doctor during regularly scheduled well-baby visits or annual checkups for your child.

Causes

Each person has two copies of chromosome 22, one inherited from each parent. If a person has DiGeorge syndrome (22q11.2 deletion syndrome), one copy of chromosome 22 is missing a segment that includes an estimated 30 to 40 genes. Many of these genes haven't been clearly identified and aren't well-understood. The region of chromosome 22 that's deleted is known as 22q11.2.

The deletion of genes from chromosome 22 usually occurs as a random event in the father's sperm or in the mother's egg, or it may occur early during fetal development. Rarely, the deletion is an inherited condition passed to a child from a parent who also has deletions in chromosome 22 but may or may not have symptoms.

Complications

The portions of chromosome 22 deleted in DiGeorge syndrome (22q11.2 deletion syndrome) play a role in the development of a number of body systems. As a result, the disorder can cause several errors during fetal development. Common problems that occur with 22q11.2 deletion syndrome include:

• Heart defects. 22q11.2 deletion syndrome often causes heart defects that could result in an insufficient supply of oxygen-rich blood. For example, defects may include a hole between the lower chambers of the heart (ventricular septal defect); only one large vessel, rather than two vessels, leading out of the heart (truncus arteriosus); or a combination of four abnormal heart structures (tetralogy of Fallot).
• Hypoparathyroidism. The four parathyroid glands in the neck regulate the levels of calcium and phosphorus in the body. 22q11.2 deletion syndrome can cause smaller than normal parathyroid glands that secrete too little parathyroid hormone (PTH), leading to hypoparathyroidism. This condition results in low levels of calcium and high levels of phosphorus in the blood.
• Thymus gland dysfunction. The thymus gland, located beneath the breastbone, is where T cells — a type of white blood cell — mature. Mature T cells are needed to help fight infections. In children with 22q11.2 deletion syndrome, the thymus gland may be small or missing, resulting in poor immune function and frequent, severe infections.
• Cleft palate. A common condition of 22q11.2 deletion syndrome is a cleft palate — an opening (cleft) in the roof of the mouth (palate) — with or without a cleft lip. Other, less visible abnormalities of the palate that may also be present can make it difficult to swallow or produce certain sounds in speech.
• Distinct facial features. A number of particular facial features may be present in some people with 22q11.2 deletion syndrome. These may include small, low-set ears, short width of eye openings (palpebral fissures), hooded eyes, a relatively long face, an enlarged nose tip (bulbous), or a short or flattened groove in the upper lip.
• Learning, behavioral and mental health problems. 22q11.2 deletion may cause problems with development and function of the brain, resulting in learning, social, developmental or behavioral problems. Delays in toddler speech development and learning difficulties are common. Some children develop attention-deficit/hyperactivity disorder (ADHD) or autism spectrum disorder. Later in life, the risk of depression, anxiety disorders and other mental health disorders increases.
• Autoimmune disorders. People who had poor immune function as children, due to a small or missing thymus, may also have an increased risk of autoimmune disorders, such as rheumatoid arthritis or Graves' disease.
• Other problems. A large number of medical conditions may be associated with 22q11.2 deletion syndrome, such as hearing impairment, poor vision, breathing problems, poor kidney function and relatively short stature for one's family.

Prevention

In some cases, DiGeorge syndrome (22q11.2 deletion syndrome) may be passed from an affected parent to a child. If you're concerned about a family history of 22q11.2 deletion syndrome, or if you already have a child with the syndrome, you may want to consult a doctor who specializes in genetic disorders (geneticist) or a genetic counselor for help in planning future pregnancies.