DiGeorge syndrome is a genetic condition caused by a small missing piece of chromosome 22, and it affects virtually every organ system in ways that range from barely noticeable to life-threatening. The deleted stretch of DNA, known as the 22q11.2 region, contains dozens of genes involved in early embryonic development, so the syndrome’s reach is remarkably wide: heart defects, immune problems, low calcium, learning difficulties, feeding trouble, and a sharply elevated risk of psychiatric illness can all trace back to that single chromosomal gap. It is among the most common microdeletion syndromes in humans, estimated to occur in roughly 1 in every 4,000 live births, yet it remains underdiagnosed because no two people with the deletion look quite the same.
What Happens at the Genetic Level
The deletion that causes DiGeorge syndrome typically removes about 3 million base pairs from the long arm of chromosome 22. This stretch sits between clusters of repetitive DNA sequences called low-copy repeats. During the formation of eggs or sperm, these repeats can misalign and recombine with each other in a process known as non-allelic homologous recombination, snipping out the segment in between.1PubMed Central. Molecular mechanisms and diagnosis of chromosome 22q11.2 rearrangements Because the repeats are a permanent feature of chromosome 22’s architecture, the deletion tends to happen spontaneously. Most cases are brand new, meaning neither parent carries the deletion. Once a person does carry it, however, each of their children has a 50 percent chance of inheriting it.2PubMed. Genetic counseling for the 22q11.2 deletion
Among the roughly 30 to 40 genes lost in a typical deletion, one stands out. Studies in mice show that knocking out a single gene called TBX1 reproduces nearly the full spectrum of DiGeorge features: heart outflow tract defects, small or absent thymus and parathyroid glands, abnormal facial structures, vertebral anomalies, and cleft palate.3PubMed. DiGeorge syndrome phenotype in mice mutant for the T-box gene, Tbx1 TBX1 encodes a transcription factor that directs the growth and specialization of progenitor cells during embryonic organ formation.4PubMed Central. Understanding the role of Tbx1 as a candidate gene for 22q11.2 deletion syndrome Losing one copy of TBX1 does not shut down development entirely, but it reduces the supply of this protein at a time when precise amounts matter, which is why the syndrome is so variable from person to person.
Heart Defects Are the Most Immediate Concern
About three-quarters of people with the 22q11.2 deletion are born with some form of congenital heart disease.5PubMed Central. Clinical manifestations of Deletion 22q11.2 syndrome (DiGeorge/Velo-Cardio-Facial syndrome) The defects tend to cluster in the outflow tract, the part of the heart that channels blood into the aorta and pulmonary artery. The most common malformations include tetralogy of Fallot, interrupted aortic arch, truncus arteriosus, pulmonary atresia with a ventricular septal defect, and isolated ventricular septal defects. Many of these require surgical repair in infancy. In fact, the presence of certain heart defects in a newborn is often what first triggers genetic testing. Among children diagnosed with tetralogy of Fallot who do not have other obvious syndromic features, roughly 6 to 7 percent still turn out to carry the 22q11.2 deletion, and those with pulmonary atresia alongside tetralogy of Fallot appear to carry the deletion at a higher rate.6International Journal of Cardiology. Frequency of 22q11.2 microdeletion in sporadic non-syndromic tetralogy of Fallot cases
Immune Function Ranges from Normal to Nearly Absent
The thymus, the small organ behind the breastbone where T cells mature, develops from the same embryonic tissue that is disrupted by the deletion. How severely the thymus is affected varies enormously. Most people with DiGeorge syndrome have a small thymus that still works well enough to produce a functional, if reduced, population of T cells. A minority have “partial” DiGeorge syndrome with moderate T-cell deficits that improve over time as the remaining thymic tissue compensates. A very small fraction, estimated at under 1 percent of all 22q11.2 deletion carriers, have “complete” DiGeorge syndrome with virtually no thymus tissue, leaving them profoundly immunodeficient in a way resembling severe combined immunodeficiency.7PubMed Central. Immunodeficiency in DiGeorge Syndrome and Options for Treating Cases with Complete Athymia
Even in the partial form, the T-cell picture is nuanced. Absolute T-cell counts tend to be low, especially early in life, though this becomes less pronounced with age. The low output of new T cells from the thymus means memory T cells make up a larger-than-normal share of the total, which changes how the immune system responds to new infections.8PubMed Central. Follicular Helper T Cells in DiGeorge Syndrome Children with DiGeorge syndrome frequently deal with recurrent viral and upper respiratory infections in their first years. Vaccination schedules sometimes need adjustment because live vaccines can pose a risk when T-cell counts are very low.
The immune dysregulation also runs in the other direction. Autoimmune conditions are more common in this population than in the general public. A multicenter study of chronic inflammatory arthritis in people with the 22q11.2 deletion found that polyarticular involvement occurred in half the cases, with arthritis persisting at last follow-up in more than half of patients. The condition showed a female predominance and required ongoing medication in most of those who achieved remission.9Orphanet Journal of Rare Diseases. Chronic inflammatory arthritis in 22q11.2 deletion (DiGeorge) syndrome: a multicentric study Other autoimmune problems reported in this population include autoimmune cytopenias and thyroid disease.
Calcium Problems Can Surface at Any Age
The parathyroid glands, which regulate calcium levels in the blood, develop from the same embryonic pouch as the thymus. When the deletion disrupts that tissue, parathyroid glands may be smaller than normal or, occasionally, absent. The result is low parathyroid hormone, which leads to low blood calcium. In a cohort of over 100 patients, low calcium was documented in about 55 percent at some point in their lives, with roughly a third experiencing it in the newborn period.10Genetics in Medicine. Parathyroid hormone reserve in 22q11.2 deletion syndrome
The timing of calcium trouble follows a characteristic pattern. Newborns are especially vulnerable because they lose the steady supply of calcium that crosses the placenta. In babies with reduced parathyroid function, this sudden cutoff can trigger seizures, tremors, or muscle spasms. For many, the low calcium is transient: once dietary intake increases and the remaining parathyroid tissue catches up, levels stabilize.11Genetics in Medicine. Endocrine aspects of the 22q11.2 deletion syndrome – Section: HYPOCALCEMIA But the risk does not disappear. Recurrences can be triggered by acute illness, surgery (particularly cardiac operations involving cardiopulmonary bypass), and the increased metabolic demands of puberty or pregnancy. Some people first develop symptoms of low calcium in adolescence or adulthood without ever having had problems as babies. A case report of a 57-year-old man newly diagnosed with the deletion after presenting with symptomatic low calcium underscores that this complication is not limited to childhood.12PubMed Central. Hypocalcemia due to 22q11.2 deletion syndrome diagnosed in adulthood
Feeding Difficulties and Swallowing Problems
Parents of infants with DiGeorge syndrome often notice feeding problems long before any genetic diagnosis is confirmed. These children commonly have trouble coordinating sucking, swallowing, and breathing, which makes bottle or breastfeeding slow and frequently interrupted by gagging or spitting up. Recurrent vomiting and constipation are typical, and the transition to solid foods often brings a new wave of gagging or outright refusal to eat.13PubMed. Dysphagia in children with a 22q11.2 deletion: unusual pattern found on modified barium swallow
Swallowing studies in these infants reveal a pattern distinct from the kind of dysphagia seen in many other conditions. The pharynx and upper esophageal area show excessive contraction and structural abnormalities that impair the smooth passage of food. In one study of 44 infants with the deletion, 93 percent had oral-phase swallowing dysfunction, 89 percent had pharyngeal-phase dysfunction, and roughly 41 percent were silently aspirating liquid into their airways, meaning food or liquid entered the trachea without triggering a cough.14PubMed. Patterns of Dysphagia and Airway Protection in Infants with 22q11.2-Deletion Syndrome Silent aspiration is particularly dangerous because caregivers and clinicians may not realize it is happening. This is why modified barium swallow studies are recommended early.
Learning, Behavior, and Speech
Developmental delays are nearly universal, though their severity varies. In a study of 100 individuals with the deletion, intellectual disability was present in just over half, while autism spectrum disorders were diagnosed in about a quarter and ADHD in about a third. Many carried overlapping diagnoses.15Research in Developmental Disabilities. Autism, ADHD, mental retardation and behavior problems in 100 individuals with 22q11 deletion syndrome Speech and language delays are especially common and often relate to a combination of factors: palatal abnormalities (including submucous cleft palate and velopharyngeal insufficiency), hearing loss from recurrent ear infections, and the neurodevelopmental profile itself. In rare cases, speech may be completely absent, requiring an intensive multidisciplinary approach involving speech therapy, occupational therapy, and special education.16PubMed Central. DiGeorge Syndrome With Absence of Speech: A Rare Case
Psychiatric Risk in Adolescence and Adulthood
One of the most studied and clinically significant aspects of DiGeorge syndrome in older patients is an elevated risk of psychotic disorders. Among people with the 22q11.2 deletion, roughly 25 percent develop schizophrenia, a rate more than 20 times higher than in the general population.17JAMA Psychiatry. Cognitive Decline Preceding the Onset of Psychosis in Patients With 22q11.2 Deletion Syndrome This makes the deletion one of the strongest known genetic risk factors for schizophrenia and has made the syndrome an important model for understanding psychosis more broadly.18PubMed Central. Schizophrenia and 22q11.2 deletion syndrome
Psychosis in this population tends to emerge in late adolescence or early adulthood, similar to the timing in people without the deletion. A key warning sign is a decline in cognitive functioning relative to the already-lower baseline typical of the syndrome. In a large study of over 400 patients, those whose cognitive performance dropped relative to the group’s average trajectory were about two and a half times more likely to go on to develop a psychotic disorder.19JAMA Psychiatry. Cognitive Decline Preceding the Onset of Psychosis in Patients With 22q11.2 Deletion Syndrome This suggests that tracking cognitive function over time could help clinicians identify those at highest risk and intervene earlier.
No Two Cases Look the Same
One of the most frustrating aspects of DiGeorge syndrome, for families and doctors alike, is its extreme variability. Two siblings carrying the exact same deletion can present very differently: one might have a serious heart defect and significant learning difficulties, while the other has only mild immune issues and some speech delay. A study of 32 families with inherited deletions found that in about 72 percent of them, the second generation was more severely affected than the first, with a greater number of features and worse overall phenotype.20PubMed Central. Intergenerational and intrafamilial phenotypic variability in 22q11.2 deletion syndrome subjects The reasons for this are not fully understood. Genes on the remaining intact chromosome 22, modifier genes elsewhere in the genome, and environmental factors during pregnancy all appear to play a role.
The size and exact position of the deletion matter, too. Most people with classic DiGeorge syndrome carry the common roughly 3-megabase deletion. But smaller, atypical deletions that sit further out along chromosome 22q11.2, between different pairs of low-copy repeats, produce a related but distinct picture. These “distal” deletions share some features with the classic syndrome, like developmental delay and mild facial differences, but they are less likely to include the characteristic outflow tract heart defects or severe immune problems.21PubMed Central. 22q11.2 distal deletion: a recurrent genomic disorder distinct from DiGeorge syndrome and velocardiofacial syndrome Even among distal deletions, smaller ones tend to produce milder phenotypes than larger ones.22Genetics in Medicine. The recurrent distal 22q11.2 microdeletions are often de novo and do not represent a single clinical entity
How It Gets Diagnosed
Historically, DiGeorge syndrome was diagnosed based on a recognizable combination of clinical features, then confirmed by a genetic test called FISH (fluorescence in situ hybridization) that uses a probe to detect the missing region on chromosome 22. FISH remains useful, especially for confirming the typical deletion, screening family members, and prenatal testing in families with a known deletion. But it has a blind spot: it can miss smaller or atypical deletions because the probe targets a specific area. Newer methods like SNP microarray testing pick up those cases. In one study, about 8 percent of patients with strong clinical suspicion but negative or inconclusive FISH results turned out to carry a deletion detectable by microarray.23PubMed Central. SNP Microarray in FISH Negative Clinically Suspected 22q11.2 Microdeletion Syndrome For newborns in intensive care or infants with only a few suggestive features, microarray is increasingly recommended as the first-line test.
There is also growing interest in catching the syndrome through newborn screening. Many U.S. states now screen newborns for severe combined immunodeficiency by measuring TREC levels, which reflect new T-cell production. Because babies with DiGeorge syndrome tend to have low T-cell output, some of them are flagged by this screen. In one screening program, about 11 percent of newborns with very low TREC values turned out to carry the 22q11.2 deletion.24PubMed. Detecting 22q11.2 Deletion Syndrome in Newborns with Low T Cell Receptor Excision Circles from Severe Combined Immunodeficiency Screening The catch is that most DiGeorge babies have TREC levels that, while lower than average, still fall within the “normal” range and would not trip the screen’s alarm.25PLOS ONE. The TREC/KREC Assay for the Diagnosis and Monitoring of Patients with DiGeorge Syndrome So SCID screening picks up the most immunologically severe cases but is not a reliable net for the syndrome as a whole. Still, those it does catch tend to have significant medical needs, and retrospective analysis shows that almost all of them had T-cell deficits and recurrent infections that warranted early intervention.26PubMed. Retrospective analysis of TREC based newborn screening results and clinical phenotypes in infants with the 22q11 deletion syndrome
Kidney and Urinary Tract Involvement
Heart, immune, and calcium problems dominate the clinical conversation, but the deletion also affects kidney development. Congenital anomalies of the kidney and urinary tract occur in roughly 30 to 37 percent of patients, making them common enough that screening ultrasounds of the kidneys and urinary system are recommended as part of the initial workup after diagnosis.27American Journal of Kidney Diseases. Urinary Anomalies in 22q11.2 Deletion (DiGeorge syndrome): From Copy Number Variations to Single-Gene Determinants of Phenotype These can range from a single kidney or kidney positioned in the wrong place to more complex structural malformations. Most are manageable but need to be identified early so that monitoring can prevent complications like urinary tract infections or, less commonly, kidney function loss.
Thymus Transplantation for Complete DiGeorge Syndrome
For the small number of infants born with no functional thymus at all, the immune deficiency is so severe that without intervention it is usually fatal. The pioneering treatment for these cases is thymus transplantation, in which cultured thymus tissue from an unrelated infant donor (typically tissue removed during cardiac surgery on another child) is implanted into the patient’s thigh muscle. In an early landmark study, five infants with complete DiGeorge syndrome received thymus grafts. T-cell function developed in four of the five; two survived with restored immunity, while the other three died from infections or unrelated issues before the graft could fully take hold. In the survivors, biopsies showed that the transplanted thymus was actively producing new T cells, and in one patient, evidence of thymus function persisted more than five years after transplantation.28PubMed. Transplantation of thymus tissue in complete DiGeorge syndrome
Since those early cases, the procedure has been refined and success rates have improved. The graft can also correct the hypoparathyroidism that accompanies complete athymia, since thymus transplant tissue sometimes includes parathyroid cells.29PubMed. Correction of both immunodeficiency and hypoparathyroidism by thymus transplantation in complete DiGeorge syndrome This dual benefit matters because it can reduce or eliminate the need for lifelong calcium and vitamin D supplementation alongside the immune benefits. Thymus transplantation remains available only at a few specialized centers, and it is reserved strictly for complete DiGeorge syndrome; patients with partial forms do not need it because their residual thymus tissue, however small, produces enough T cells to provide meaningful protection.
Parkinson’s Disease and Aging With the Deletion
As life expectancy for people with DiGeorge syndrome has improved with better cardiac surgery, infection management, and overall care, a new set of adult-onset concerns has emerged. One of the most striking is an association with early-onset Parkinson’s disease. A review of cases found that the average age at which motor symptoms appeared was about 39, with over 70 percent developing Parkinson’s before age 45, decades earlier than typical.30PubMed. Typical features of Parkinson disease and diagnostic challenges with microdeletion 22q11.2 The clinical picture and response to standard Parkinson’s medications appear similar to what is seen in people without the deletion. The connection is thought to involve genes within the deleted region that play a role in dopamine neuron survival, though the exact mechanism is still being worked out. This finding has practical implications: adults with the deletion who develop tremor, stiffness, or slowness of movement should be evaluated for Parkinson’s rather than having symptoms attributed solely to psychiatric medication side effects, a misattribution that can easily occur given the high rate of psychotropic drug use in this population.
Why So Many Names for One Condition
You may encounter this syndrome referred to as DiGeorge syndrome, velocardiofacial syndrome, Shprintzen syndrome, conotruncal anomaly face syndrome, or simply 22q11.2 deletion syndrome. These labels all describe the same underlying genetic event but were coined by different specialists who each noticed a different facet of the condition first. Cardiologists saw the heart defects and thymic absence and called it DiGeorge syndrome. Speech pathologists and craniofacial surgeons noticed the palatal and facial features and called it velocardiofacial syndrome. An attempt in the 1990s to unify the names under the acronym CATCH 22 (Cardiac defects, Abnormal facies, Thymic hypoplasia, Cleft palate, Hypocalcemia) was initially accepted by the genetics community but eventually fell out of favor.31Progress in Pediatric Cardiology. Historical perspectives of velo-cardio-facial syndrome – Section: Avoidance of the acronym CATCH 22 Today, “22q11.2 deletion syndrome” is the most precise term and the one increasingly preferred in medical literature because it names the cause rather than a subset of symptoms. In practice, all the names persist, and you are likely to hear different ones depending on which specialist you are talking to.