Complete DiGeorge Syndrome a.k.a. 22g11.2 Deletion Syndrome

What is complete DiGeorge syndrome?

DiGeorge syndrome, also known as 22g11.2 deletion syndrome, is a primary immunodeficiency disease. Primary immunodeficiency diseases are inherited immune system disorders, caused by a mutated gene that prevents the body’s immune system from fighting infection effectively. In DiGeorge syndrome, a small piece near the middle of the 22^nd chromosome is deleted. An even rarer form of DiGeorge syndrome is called complete DiGeorge syndrome. When the disease is in its complete form, that means the patient is athymic, or it has no thymus gland. The thymus gland, located under the breastbone, is where T-cells (a type of white blood cell) mature. Mature T-cells help to fight infection. Since patients with complete DiGeorge syndrome have no thymus gland, they will often have poor immune function and frequent infections, because they have an insufficient number of antibodies. DiGeorge syndrome affects about 1 in 4,000 people. Because primary immunodeficiency disorders are genetic in nature, they are usually passed from one generation to the next, but not always. In the case of DiGeorge syndrome, the disease is only rarely inherited. There are many instances where a person is born with a mutated gene, and is the only one in the family to have the disease.

What are the symptoms of complete DiGeorge syndrome?

The symptoms of this disease vary widely, so it is important to note that a patient will not exhibit every symptom listed below. Some symptoms are apparent at birth, while others develop during early childhood. They include the following:

• Heart abnormalities and defects
• Poor immune system function
• Cleft palate
• No thymus gland
• Frequent infections
• Seizures caused by low levels of calcium in the blood
• Distinctive facial features: relatively long face, enlarged nose, underdeveloped chin, low-set ears, wide-set eyes
• Developing rheumatoid arthritis and/or Graves’ disease
• Breathing problems
• Kidney abnormalities
• Difficulty feeding
• Gastrointestinal issues
• Hearing loss
• Poor vision
• Short stature
• Developmental delay—growth, speech development, learning disabilities
• Poor muscle tone
• Mental illness
• ADHD
• Autism spectrum disorders

What causes complete DiGeorge syndrome?

Chromosomes carry the genetic characteristics of individuals, and are located in the nucleus of all body cells. Humans have 23 pairs of chromosomes, so 46 chromosomes in total. DiGeorge syndrome occurs when a small piece of chromosome 22 is deleted, in a location designated q11.2—hence the name, 22q11.2 deletion syndrome. The loss of the genes in that part of the chromosome is what causes many of the disease’s characteristic symptoms. Most cases of DiGeorge syndrome are not inherited. The deletion in the chromosome usually occurs as a random event during the formation of reproductive cells or in early fetal development. In the rarer chance that it is inherited, only one copy of the mutated gene is needed for the disease to be inherited—so, only one parent must pass it on for the condition to occur. This is called autosomal dominant.

How is complete DiGeorge syndrome diagnosed?

Complete DiGeorge syndrome is diagnosed using the following procedures:

• A lab test (blood test) that can detect the deletion in chromosome 22
• FISH studies (Fluorescence in situ hybridization), which map the genetic material in human cells
• Routine chromosome (cytogenetic) testing

What are the treatments for complete DiGeorge syndrome?

While there is no cure for the disease, treatments can usually correct critical problems. Since symptoms are so varied, patients will need a team of specialized working together to mitigate them. Treatment includes, but is not limited to:

• Transplanting thymus tissue, specialized cells from bone morrow, or specialized blood cells that fight disease to mitigate the risk of infection due to no thymus gland
• Surgery to repair heart defects
• Vaccines and medications to treat infection
• Calcium and vitamin D supplements to combat low levels
• Surgery to repair cleft palate
• Speech, occupational, and/or developmental therapy
• Mental health care
• Genetic counseling

Where can I find out more about complete DiGeorge syndrome?

• Mayo Clinic
• National Organization for Rare Disorders (NORD)
• NIH