DiGeorge syndrome

Lore & Background

DiGeorge syndrome is typically due to the deletion of 30 to 40 genes in the middle of chromosome 22 at a location known as 22q11.2. About 90% of cases occur due to a new mutation during early development, while 10% are inherited. It is autosomal dominant, meaning that only one affected chromosome is needed for the condition to occur. Diagnosis is suspected based on the symptoms and confirmed by genetic testing. The features vary widely, even among members of the same family, and affect many parts of the body. Characteristic signs and symptoms may include birth defects such as congenital heart disease, defects in the palate, learning disabilities, mild differences in facial features, and recurrent infections. Infections are common in children due to problems with the immune system's T cell-mediated response, which in some patients is due to an absent or hypoplastic thymus. Affected individuals may also have kidney abnormalities, significant feeding difficulties, gastrointestinal issues, hypothyroidism, hypoparathyroidism, thrombocytopenia, and psychiatric illnesses.

Reader's Guide

DiGeorge syndrome is significant as a common microdeletion syndrome with highly variable expression, affecting multiple organ systems. It was first described in 1968 by American physician Angelo DiGeorge, and its genetic basis was determined in late 1981. The syndrome occurs in about 1 in 4,000 people and is caused by a heterozygous deletion of part of the long arm of chromosome 22 (22q11.2). Approximately 80-90% of patients have a deletion of 3 Mb and 8% have a deletion of 1.5 Mb. The number of genes affected has been cited as approximately 30 to 50. The disorder has an autosomal dominant inheritance pattern, with most cases resulting from a de novo deletion. Although there is no cure, treatment can improve symptoms through a multidisciplinary approach. Long-term outcomes depend on the symptoms present and the severity of the heart and immune system problems; with treatment, life expectancy may be normal. The syndrome is associated with a 20 to 30-fold increased risk of schizophrenia, and about 30% of adults have at least one episode of psychosis, with about a quarter developing schizophrenia by adulthood. Individuals also have a higher risk of developing early onset Parkinson's disease. The features can be summarized using the mnemonic CATCH-22, which includes Cardiac abnormality, Abnormal facies, Thymic aplasia or hypoplasia, Cleft palate, and Hypocalcemia/hypoparathyroidism.

Did You Know?

• DiGeorge syndrome is also known as 22q11.2 deletion syndrome.
• About 90% of cases occur due to a new mutation during early development, while 10% are inherited.
• The syndrome is associated with a 20 to 30-fold increased risk of schizophrenia.
• The mnemonic CATCH-22 is used to summarize salient features, with the 22 signifying the chromosomal abnormality on the 22nd chromosome.

The Genetic Blueprint Behind the Syndrome

DiGeorge syndrome, more precisely called 22q11.2 deletion syndrome, traces its origin to a tiny stretch of missing DNA on the long arm of chromosome 22. The affected region, designated 22q11.2, sits in the middle of the chromosome and normally houses roughly thirty to forty genes. When that segment is lost, the cascade of developmental consequences that follows can touch nearly every organ system in the body. Inheritance follows an autosomal dominant pattern, meaning a single copy of the altered chromosome is sufficient to produce the condition. In the vast majority of cases—approximately ninety percent—the deletion arises as a brand-new mutation during early embryonic development rather than being passed down from a parent. The remaining ten percent are inherited from an affected individual. The condition affects roughly one in every four thousand people. American physician Angelo DiGeorge first described the clinical picture in 1968, and it was not until late 1981 that researchers identified the underlying chromosomal deletion responsible.

A Mosaic of Symptoms: The CATCH-22 Profile

Because the syndrome exhibits incomplete penetrance, no two individuals present in exactly the same way, even siblings who carry the identical deletion can show markedly different clinical pictures. Clinicians often rely on the mnemonic CATCH-22 to catalog the hallmark features: cardiac abnormality (including interrupted aortic arch, truncus arteriosus, and tetralogy of Fallot), abnormal facial features such as hypertelorism, a tubular nose with anteverted nostrils, a short philtrum, and mandibular hypoplasia; thymic aplasia or hypoplasia; cleft palate; and hypocalcemia or hypoparathyroidism in early life. The "22" simply anchors the chromosomal location. Beyond these core signs, affected individuals may also face kidney abnormalities, significant feeding difficulties as infants, gastrointestinal motility problems leading to constipation, and a weakened T-cell–mediated immune response that makes recurrent infections a persistent childhood challenge. The severity spectrum is broad, ranging from relatively mild presentations to life-threatening cardiac and immune complications.

Cognitive, Psychiatric, and Communication Challenges

The neuropsychological profile of individuals with 22q11.2 deletion syndrome is distinctive. Most score in the below-borderline range on IQ tests, with verbal abilities typically outpacing nonverbal ones. Some manage in mainstream classrooms while others require special education or home schooling. A particularly concerning dimension is psychiatric risk: the microdeletion confers a twenty- to thirty-fold increase in schizophrenia susceptibility. Approximately thirty percent of affected adults experience at least one psychotic episode, and roughly a quarter go on to develop full schizophrenia. The condition also elevates the risk of early-onset Parkinson's disease, though diagnosis can be delayed by as much as a decade because antipsychotic medications used to treat psychosis can mimic parkinsonian symptoms. In the speech and language domain, about sixty-nine percent of children have palatal abnormalities that produce velopharyngeal inadequacy, causing air to escape through the nose and creating a hypernasal quality that reduces intelligibility. Expressive vocabulary acquisition is often severely delayed, with some children still not verbal by age two or three, and school-age children continue to struggle with narrative recall and complex sentence production.

Diagnosis, Management, and the Road Ahead

There is currently no cure for 22q11.2 deletion syndrome, but a well-coordinated, multidisciplinary treatment plan can meaningfully improve quality of life. Because the condition can involve the heart, immune system, endocrine glands, kidneys, digestive tract, and many other organ systems, care typically requires input from cardiologists, immunologists, endocrinologists, speech therapists, and other specialists working in concert. Diagnosis is usually suspected when a cluster of characteristic symptoms—congenital heart defects, hypocalcemic convulsions in a newborn, recurrent infections, or distinctive facial features—prompts a clinician to order confirmatory genetic testing. Long-term prognosis hinges largely on the severity of cardiac and immune involvement; individuals with milder presentations and effective treatment can expect a near-normal life expectancy. The syndrome was first clinically described in 1968 by American physician Angelo DiGeorge, and the specific chromosomal deletion was not identified until late 1981, a gap of more than a decade that underscores how slowly the genetic underpinnings of many disorders are unraveled.

Gallery