DiGeorge syndrome(s)

Phenotype of patients with late diagnosis of 22q11 deletion: a review and retrospective study

BACKGROUND

Chromosome 22q11.2 deletion syndrome (22q11DS) is the most common microdeletion syndrome, typically presenting in neonates with congenital cardiac anomalies, hypocalcaemia and thymic hypoplasia. Some patients are diagnosed later in adolescence and adulthood, with less known about the clinical phenotype of these patients.

AIM

To summarise key clinical features in cases of 22q11DS diagnosed during adolescence and adulthood.

METHODS

This is a retrospective cohort study of 22q11DS patients diagnosed after 13 years of age over 2010-2021, with a literature review of published cases highlighting other late diagnoses. The study was performed in a large multicentre tertiary health network in Melbourne, Australia. Patients diagnosed with 22q11DS after the age of 13 years were included in the study. Main outcome measures were key clinical features in cases of late diagnosis of 22q11DS.

RESULTS

A literature search yielded 53 published case reports and one cohort study for review (62 subjects). Additionally, 10 cases of late diagnosis of 22q11DS were identified through a retrospective electronic medical chart review. Findings suggest that intellectual disability and learning difficulties, hypocalcaemia with hypoparathyroidism and facial dysmorphism remain key features in patients with a late diagnosis of 22q11DS, with hypocalcaemia being the most common presentation leading to diagnosis. Patients diagnosed in adulthood may lack classical clinical features of congenital cardiac anomalies and thymic hypoplasia. Immunological consequences of 22q11DS are also an important late-onset consideration. Atypical features may include basal ganglia calcification.

CONCLUSIONS

Chromosome 22q11DS has diverse clinical features and a highly variable phenotype, likely contributing to underdiagnosis and later diagnoses.

Chromosome 22q11.2 deletion syndrome and DiGeorge syndrome

Chromosome 22q11.2 deletion syndrome is the most common microdeletion syndrome in humans. The effects are protean and highly variable, making a unified approach difficult. Nevertheless, commonalities have been identified and white papers with recommended evaluations and anticipatory guidance have been published. This review will cover the immune system in detail and discuss both the primary features and the secondary features related to thymic hypoplasia. A brief discussion of the other organ system involvement will be provided for context. The immune system, percolating throughout the body can impact the function of other organs through allergy or autoimmune disease affecting organs in deleterious manners. Our work has shown that the primary effect of thymic hypoplasia is to restrict T cell production. Subsequent homeostatic proliferation and perhaps other factors drive a Th2 polarization, most obvious in adulthood. This contributes to atopic risk in this population. Thymic hypoplasia also contributes to low regulatory T cells and this may be part of the overall increased risk of autoimmunity. Collectively, the effects are complex and often age-dependent. Future goals of improving thymic function or augmenting thymic volume may offer a direct intervention to ameliorate infections, atopy, and autoimmunity.

Immune and Genetic Features of the Chromosome 22q11.2 Deletion (DiGeorge Syndrome)

PURPOSE OF REVIEW

This review provides an update on the progress in identifying the range of immunological dysfunction seen in DiGeorge syndrome and on more recent diagnostic and treatment approaches.

RECENT FINDINGS

Clinically, the associated thymic hypoplasia/aplasia is well known and can have profound effects on T cell function. Further, the humoral arm of the immune system can be affected, with hypogammaglobulinemia and poor vaccine-specific antibody response. Additionally, genetic testing utilizing chromosomal microarray demonstrates a small but significant number of 22q11 deletions that are not detectable by standard FISH testing. The recent addition of a TREC assay to newborn screening can identify a subset of infants whose severe immune defects may result from 22q11 deletion. This initial presentation now also places the immunologist in the role of "first responder" with regard to diagnosis and management of these patients. DiGeorge syndrome reflects a clinical phenotype now recognized by its underlying genetic diagnosis, chromosome 22q11.2 deletion syndrome, which is associated with multisystem involvement and variable immune defects among patients. Updated genetic and molecular techniques now allow for earlier identification of immune defects and confirmatory diagnoses, in this disorder with life-long clinical issues.

Probing human cardiovascular congenital disease using transgenic mouse models

Congenital heart defects (CHDs) impact in utero embryonic viability, children, and surviving adults. Since the first transfer of genes into mice, transgenic mouse models have enabled researchers to experimentally study and genetically test the roles of genes in development, physiology, and disease progression. Transgenic mice have become a bona fide human CHD pathology model and their use has dramatically increased within the past two decades. Now that the entire mouse and human genomes are known, it is possible to knock out, mutate, misexpress, and/or replace every gene. Not only have transgenic mouse models changed our understanding of normal development, CHD processes, and the complex interactions of genes and pathways required during heart development, but they are also being used to identify new avenues for medical therapy.

A novel role for transcription factor Lmo4 in thymus development through genetic interaction with Cited2

Deletion of the transcriptional modulator Cited2 in the mouse results in embryonic lethality, cardiovascular malformations, adrenal agenesis, cranial ganglia fusion, exencephaly, and left-right patterning defects, all seen with a varying degree of penetrance. The phenotypic heterogeneity, observed on different genetic backgrounds, indicates the existence of both genetic and environmental modifiers. Mice lacking the LIM domain-containing protein Lmo4 share specific phenotypes with Cited2 null embryos, such as embryonic lethality, cranial ganglia fusion, and exencephaly. These shared phenotypes suggested that Lmo4 may be a potential genetic modifier of the Cited2 phenotype. Examination of Lmo4-deficient embryos revealed partially penetrant cardiovascular malformations and hypoplastic thymus. Examination of Lmo4;Cited2 compound mutants indicated that there is a genetic interaction between Cited2 and Lmo4 in control of thymus development. Our data suggest that this may occur, in part, through control of expression of a common target gene, Tbx1, which is necessary for normal thymus development.

Immunological abnormalities in CHARGE syndrome

Immune deficiency can be part of CHARGE syndrome but often receives only limited attention. We present two patients with CHARGE syndrome confirmed CHD7 mutations who had severe T-cell deficiency, and review 15 CHARGE patients from the literature with immunological problems. Most of them had severe T-cell deficiency, although the spectrum also included mild T-cell deficiency and isolated humoral immune deficiency. We conclude that immunodeficiency can form an important symptom in CHARGE syndrome although the frequency and exact nature are still insufficiently known. We propose to evaluate immune functions in all CHARGE syndrome patients, to estimate the frequency and nature of the accompanying immunodeficiency, and to obtain better data regarding prognosis and management.

Di-George syndrome presenting with hypocalcaemia in adulthood: two case reports and a review

This report describes two cases of Di-George syndrome presenting with hypoparathyroidism in adulthood. The first patient presented with profound hypocalcaemia that resulted in a generalised seizure. Routine investigations revealed hypoparathyroidism. The clue to her underlying condition was the postnatal death of her young child. This case shows that Di-George syndrome can present in adulthood with hypocalcaemia in the absence of other classic features of this condition. This has enormous implications for future family planning and may also have important health implications. The second patient, diagnosed on routine blood testing, had previously suffered with a congenital heart condition, but the syndrome was not revealed until she was of postmenopausal age. These two patients show that Di-George syndrome can present in adulthood with hypocalcaemia. This is an important observation because the condition has profound implications for health and family planning.

Congenital abnormalities of body patterning: embryology revisited

Many of the developmental mechanisms and molecular pathways that underlie fundamental features of body patterning are shared by all vertebrates, and some have even been conserved across evolution from invertebrates to vertebrates. Defects in such processes are a common cause of congenital malformation syndromes, and rapid progress is being made in elucidating their embryological and genetic basis. Here, I focus on three examples, each of which has been the subject of recent advances, and which together illustrate many of the most interesting and important aspects of these disorders. The first example is the development of the pharyngeal apparatus and its perturbation in DiGeorge's syndrome; the second is the induction and differentiation of the forebrain and its perturbation in holoprosencephaly; and the third is the role played by the human HOX genes in congenital malformations.

Pulmonary infections in immunocompromised hosts: the importance of correlating the conventional radiologic appearance with the clinical setting

The lung is one of the most frequently involved organs in a variety of complications in the immunocompromised host. Among the pulmonary complications that occur in this kind of patient, infection is the most common and is associated with high morbidity and mortality. Although chest radiography and computed tomography (CT) are essential diagnostic tools, radiologists often have difficulty in establishing the correct diagnosis on the basis of radiologic findings alone. The reasons are that the immunocompromised host is potentially susceptible to infection from many different microorganisms and that radiologic findings are seldom specific for the detection of a particular pathogen. Experience has shown that a particular clinical setting predisposes patients to infection by particular pathogens. The setting comprises (a) the specific epidemiologic or environmental exposure, (b) the type of underlying immune defect, (c) the duration and severity of immune compromise, and (d) the progression rate and pattern of the radiologic abnormality. Correlating the radiologic appearance with the clinical setting can expedite diagnosis and appropriate therapy. In this review, the authors describe the clinical settings that are helpful in choosing the radiologic approach to treatment of the immunocompromised host who presents with suspected pulmonary infection.

Head and neck anomalies related to the branchial apparatus

An understanding of the branchial apparatus and its anomalies may lead to greater precision in the clinical diagnosis and management of these congenital head and neck lesions. Although branchial anomalies have been well described, controversial issues, such as the branchial origin of lateral cervical cysts and the differentiation between third and fourth branchial pouch sinuses, remain unresolved.

Structural airway anomalies in patients with DiGeorge syndrome: a current review

DiGeorge Syndrome is a genetic disorder characterized by either absence or hypoplasia of the thymus and the parathyroid glands. Patients with this syndrome also have a high incidence of cardiovascular malformations and facial dysmorphism. Structural airway anomalies have also been described, albeit infrequently. Tracheoesophageal fistula, short trachea with reduced numbers of tracheal rings, abnormal thyroid cartilage, laryngomalacia, tracheomalacia, and bronchomalacia have been recognized in these patients. We review all previously reported patients with DiGeorge syndrome and lower airway anomalies. In addition, we present 2 patients with DiGeorge syndrome who were each found to have an aberrant right tracheal bronchus. Structural airway anomalies can be a cause of morbidity and mortality in patients with DiGeorge syndrome. Prompt, thorough evaluation of the upper and lower airway in these patients is essential.

DiGeorge anomaly: a comparative study of the clinical and immunologic characteristics of patients positive and negative by fluorescence in situ hybridization

BACKGROUND

DiGeorge anomaly (DGA) is defined as a field defect characterized by dysmorphic facies, hypoparathyroidism, congenital heart defects, and a deficiency in cell-mediated immunity, usually associated with a microdeletion in chromosome 22q11.2. Data correlating clinical and genetic information, especially in terms of the extent of the immunodeficiency and infectious complications, are scant.

OBJECTIVE

The goal of this study was to define the severity of the immunodeficiency and infectious illnesses in DGA patients with characteristic clinical and genetic findings and compare them with a similar group of patients without a microdeletion in chromosome 22q11.2.

METHODS

A retrospective chart review of patients referred for evaluation of DGA to our immunology service from 1989 to 1995 was conducted. Clinical and immunologic data were collected from their initial evaluation. Patients meeting at least 3 of 4 of these criteria were considered to meet strict clinical diagnostic criteria for DGA, and the results of analysis for a microdeletion in chromosome 22q11.2 for each patient was noted.

RESULTS

Sixteen of the 22 patients meeting strict clinical criteria for DGA were available for analysis for the microdeletion at chromosome 22q.11.2. Of these, 13 (81%) were positive by fluorescence in situ hybridization (FISH); 9 of 13 (69%) had low CD3 numbers, 6 of 10 assayed (60%) had low thymulin levels; 10 of 13 (77%) had low CD4 numbers, and 10 of 12 (83%) had absent or small thymus glands. B cells were increased in 9 of 13 (69%) patients. Mitogen and antigen responses were normal in 6 of 7 (86%) patients tested. Eight of 13 (62%) had a history of increased frequency of infectious illnesses. All had recurrent respiratory infections, including sinusitis, otitis media, and pneumonia. Three of the 16 patients tested (19%) were FISH negative. Two of 3 (67%) had low CD3 and CD4 numbers. B cells were elevated in all patients. All had recurrent respiratory infections, low thymulin levels, and absent thymus glands.

CONCLUSIONS

Contrary to traditional descriptions, this group of clinically and genetically defined patients with DGA had a predominantly mild cell-mediated immunodeficiency syndrome usually associated with infections characteristic of humoral immunodeficiencies. The patients who were FISH positive did not differ significantly from those that were FISH negative in terms of clinical and immunologic findings or infectious complications.

Oral findings in DiGeorge syndrome: clinical features and histologic study of primary teeth

OBJECTIVE

For the purpose of supplementing the shortage of dental information about DiGeorge syndrome, we report two cases of the syndrome seen in Japanese boys.

STUDY DESIGN

Two cases were compared with respect to orofacial and dental findings; one was a case of complete DiGeorge syndrome and the other a case of partial DiGeorge syndrome. Extracted deciduous teeth from the two boys underwent histologic study.

RESULTS

Each patient showed systemic developmental delay, hypocalcemia, and slight mental retardation. In the orofacial area, hypertelorism, a short philtrum, thick and reflected lips, and hypoplasia of the nasopharynx were also observed. A dental examination showed delayed formation and eruption of permanent teeth, aplasia of the nasopharynx, and enamel hypoplasia along with enamel hypocalcification. Structural streaks with increased calcification were histologically detected in the deciduous tooth from the patient with complete DiGeorge syndrome.

CONCLUSIONS

Common characteristic orofacial and dental findings were noted in the two DiGeorge syndrome cases. Furthermore, histologic study of the deciduous tooth from the boy with complete DiGeorge syndrome suggests that there was some relationship between transient relative hypercalcemia and dentinal hypermineralized streaking of the tooth.

Velocardiofacial syndrome

Velocardiofacial syndrome is a syndrome of multiple anomalies that include cleft palate, cardiac defects, learning difficulties, speech disorder and characteristic facial features. It has an estimated incidence of 1 in 5000. The majority of cases have a microdeletion of chromosome 22q11.2. The phenotype of this condition shows considerable variation, not all the principal features are present in each case. Identification of the syndrome can be difficult as many of the anomalies are minor and present in the general population.

Features of DiGeorge syndrome and CHARGE association in five patients

We report on five patients presenting with features of two congenital disorders, DiGeorge syndrome (DGS) and CHARGE association. CHARGE association is usually sporadic and its origin is as yet unknown. Conversely, more than 90% of DGS patients are monosomic for the 22q11.2 chromosomal region. In each of the five patients, both cytogenetic and molecular analysis for the 22q11.2 region were normal. In view of the broad clinical spectrum and the likely genetic heterogeneity of both disorders, these cases are consistent with the extended phenotype of either DGS without 22q11.2 deletion or CHARGE association, especially as several features of CHARGE association have been reported in rare patients with 22q11.2 deletion association phenotypes. On the other hand, these could be novel cases of an independent association involving a complex defect of neural crest cells originating from the pharyngeal pouches.

Vestibular abnormalities in charge association

We report the vestibular abnormalities in 5 patients with the CHARGE association (Coloboma, Heart disease, Atresia of choanae, Retarded growth and development and/or central nervous system anomalies, Genital hypoplasia, and Ear anomalies). All patients had absent vestibular function as indicated by absent vestibulo-ocular reflexes and severe imbalance on simultaneous deprivation of proprioception and vision, as well as delayed motor development. All 6 semicircular canals were aplastic in each of the patients. While cochlear function was severely reduced in 6 of the 10 ears, it was absent only in 3 ears and was actually intact below 3 kHz in 1 ear. All 10 bony cochleas were present on computed tomography, and although 7 appeared abnormal, 3 appeared normal. This study confirms that absence of the bony semicircular canals in the presence of a bony cochlea is a characteristic finding in CHARGE association. It also demonstrates that these disproportionate structural abnormalities are reflected in the functional abnormalities: absent vestibular function with preservation of some cochlear function.

Molecular genetic approaches to the study of human craniofacial dysmorphologies

Craniofacial dysmorphologies are common, ranging from simple facial disfigurement to complex malformations involving the whole head. With the advent of gene mapping and cloning techniques, the genetic element of both simple and complex human craniofacial dysmorphologies can be investigated. For many of the dysmorphic syndromes, it is possible to find families that display a particular phenotype in either an autosomal dominant, recessive, or X-linked manner. This article focuses on a subgroup of craniofacial dysmorphologies, covering these three main inheritance patterns, that are being studied using molecular biology techniques: DiGeorge syndrome, Treacher Collins syndrome, Greig cephalopolysyndactyly syndrome, acrocallosal syndrome, amelogenesis imperfecta, and X-linked cleft palate with ankyloglossia. Once the mutated or deleted gene or genes for each syndrome have been cloned, patterns of normal and abnormal craniofacial development should be elucidated. This should enhance both diagnosis and treatment of these common and disfiguring disorders.

Unmasking of latent hypoparathyroidism in a child with partial DiGeorge syndrome by ethylenediaminetetraacetic acid infusion

DiGeorge syndrome is a rare congenital anomaly with a wide range of clinical manifestations. This syndrome is usually associated with hypocalcaemia resulting from primary hypoparathyroidism. We report here a case of an 8-year-old boy with partial DiGeorge syndrome who presented initially with neonatal hypocalcaemia, but was subsequently normocalcaemic. Latent hypoparathyroidism was unmasked by a diagnostic EDTA infusion resulting in hypocalcaemia without a parathyroid hormone response. We propose that EDTA infusions can be useful in the diagnosis of latent hypoparathyroidism in children.

Maldescent of the thymus: 34 necropsy and 10 surgical cases, including 7 thymuses medial to the mandible

Among 3236 pediatric necropsies over 23 years, abnormal position of thymic tissue was recorded in 34 cases. Cardiac anomalies, predominantly those seen in DiGeorge syndrome, were present in 24; 3 had noncardiac anomalies only, 4 had other diseases, and 3 were sudden infant deaths. Mediastinal thymic tissue was absent in 22 cases, small or unilateral in 7, and normal in 5. The maldescended thymic tissue was unilateral in 18, bilateral in 11, and multiple on one or both sides in 5. It was situated near the thyroid gland in 19, lower in the neck in 6, and higher in 9, including 7 medial to the submandibular salivary gland and 1 at the base of the skull. The maldescended tissue approached the size of a normal lobe of thymus in eight and was 2.4 to 0.1 cm in the remainder. Over the same period, in only two cases was no thymic tissue found. Among 68,000 surgical specimens over 40 years, there were 10 cases of ectopic thymus in the neck, including 1 cutaneous and 4 cystic. This frequency of thymic tissue in the neck may explain why lymphoid tissues are sometimes relatively normal in cases of absent mediastinal thymus and behooves a search in the submandibular salivary gland region and higher before diagnosing thymic agenesis.

A case of incomplete DiGeorge syndrome associated with partial monosomy 22q11.1 due to maternal 14;22 translocation

We report a boy with some clinical symptoms compatible with a diagnosis of incomplete DiGeorge syndrome. He had a dismorphic face, micrognathia, cleft palate, and heart anomalies similar to DiGeorge syndrome, but lacked aplasia of the thymus or hypoparathyroidism typical of the syndrome. High-resolution banding analysis revealed that his karyotype was 45,XY,-14,-22, +der(14)(14pter----14q32.32::22q11.21----22qter), the consequence of a maternal reciprocal translocation between chromosomes 14 and 22. Precise localization of the gene responsible for the present DiGeorge syndrome was assigned to subband 22q11.1.

DiGeorge syndrome in a child with partial monosomy of chromosome 22

A girl with severe neonatal hypocalcaemia, thymic hypoplasia, congenital heart disease and mental retardation in combination with a partial monosomy of chromosome 22, del(22)(pter-q11.3), is reported. Nine other patients with an association between partial monosomy 22 and a DiGeorge syndrome have been reported earlier, and this combination probably constitutes a deletion syndrome similar to the Prader-Willi and the aniridia-Wilms' tumour syndromes. However, the deletion of chromosome 22 is mostly due to a translocation, with trisomy for another chromosomal segment. Such a mechanism may explain the different clinical features seen in patients with partial monosomy 22. In the present case there was an unbalanced translocation with a probable trisomy of the short arm of chromosome 20 combined with the partial monosomy 22. Cytogenetic investigation with high resolution banding techniques is indicated in patients with thymic aplasia and suspected DiGeorge syndrome.

Flow cytometric analysis of lymphocyte subpopulations in infants with congenital heart disease

Premortem diagnosis of the DiGeorge syndrome and its partial variants relies on the demonstration of a primary defect in cell-mediated immunity, generally in the setting of an infant with congenital heart disease, hypocalcemia, absence of a thymic shadow, and typical dysmorphic features. Although T-cell enumeration is considered a vital part of the diagnostic evaluation, no studies to date have addressed the issue of appropriate reference data in infants with congenital heart disease. We therefore undertook a prospective descriptive study of lymphocyte phenotype analysis in 27 nontransfused infants undergoing diagnostic cardiac catheterization. Striking differences were seen between patients and adult controls in means percentages and numbers of most lymphocyte subsets analyzed. Few differences were found in comparing the patient data to values for age-matched control infants without heart disease. The data are discussed with reference to published values for patients with partial DiGeorge syndrome. It is concluded that lymphocyte phenotype analysis in the diagnostic evaluation of patients with suspected DiGeorge syndrome must utilize appropriate reference values.

Aplastic anaemia complicating adenovirus infection in DiGeorge syndrome

An 18-month-old child with partial DiGeorge syndrome developed aplastic anaemia during an acute adenovirus infection. Assessment of the child's immune system revealed T-cell subset abnormalities consistent with DiGeorge syndrome. A possible link between the underlying immune deficiency and the observed complication is suggested.

The association between immunodeficiency and congenital heart disease

The predilection of children with congenital heart disease (CHD) to infection may be explained in part by an underlying immunodeficiency disorder. Some 13 syndromes in which immunodeficiency and CHD may coexist have been reported in the medical literature. In addition, immunoglobulin and T-cell deficiencies have been found in nonsyndromal patients with CHD. The diagnosis of immunodeficiency should be entertained in such children, as early recognition of an immunodeficiency disorder can result in improved antimicrobial and immunological management.

Spectrum of Di George syndrome in patients with truncus arteriosus: expanded Di George syndrome

A study of 26 patients with truncus arteriosus showed a high prevalence of facial dysmorphism, aortic arch abnormalities, extracardiac malformations, and significant prenatal risk factors. There was little evidence of parathyroid or thymic abnormalities. However, there was laboratory evidence of immune deficiency, especially T-helper lymphocytes, and clinical evidence of predilection to infection. These findings suggest that patients with truncus arteriosus belong to the spectrum of the Di George syndrome.

Interrupted right aortic arch in DiGeorge syndrome

The clinical and necropsy findings in four cases of interrupted right aortic arch and right descending aorta associated with DiGeorge syndrome (congenital absence or hypoplasia of the thymus and parathyroids) are described. All patients had a mirror image of type B interruption, namely a right aortic arch with reversed branching pattern and an interruption between the right common carotid and right subclavian artery. In two patients there was a doubly committed subarterial ventricular septal defect and in the two other patients there was a perimembranous septal defect. Three patients had a bicuspid aortic valve. In a consecutive series of 185 necropsies in infants and children with congenital heart disease there were no cases of interrupted right aortic arch that were not associated with DiGeorge syndrome. These observations and previous reports indicate that the concurrence of these two rare conditions is more than fortuitous. In patients with an interrupted aortic arch the clinician should be aware of the common association with DiGeorge syndrome. If the interruption is associated with a right-sided descending aorta it is highly probable that the patient has DiGeorge syndrome.

Features of di George syndrome in a child with 45,XX,-3,-22,+der(3),t(3;22)(p25;q11)

A child with an unbalanced translocation resulting in monosomy for chromosomes 22 (q11----pter) and 3(p25----pter) is described. Although no immunological dysfunction could be demonstrated, the abnormalities found are similar to those seen in the di George syndrome which has been associated with monosomy for the same region of chromosome 22.

Thyrocalcitonin-containing cells in the Di George anomaly

The Di George syndrome is an anomaly characterized by the complete or partial absence of derivatives of the third and fourth pharyngeal pouches often associated with defective development of the third, fourth, and sixth aortic arches leading to absence or hypoplasia of the thymus and parathyroid glands and to cardiovascular anomalies. The fifth pharyngeal pouch, often considered a part of the fourth pouch, gives rise to the ultimobranchial body (UB), which becomes incorporated into the thyroid gland and is thought to be the source of thyroid C cells. Robinson suggested that complete or partial absence of the UB should be considered a part of the Di George anomaly. To substantiate this theory, the thyroid glands of 11 patients with the Di George syndrome and 11 age-matched control infants were examined immunohistochemically using the immunoperoxidase technique for presence or absence of thyrocalcitonin (TC)-containing cells. Only three of 11 patients with the Di George syndrome had TC-containing cells in their thyroid glands (27 per cent), and nine of 11 control infants had these cells (82 per cent). It is concluded that thyroid C cell deficiency is present in most patients with Di George anomaly, suggesting a relationship between these cells and development of derivatives of the third through fifth visceral pouches. Furthermore, there is a spectrum of deficiency of thyroid C cells in these individuals comparable with the spectrum of partial to complete absence of third and fourth pharyngeal pouch derivatives regarding thymus and parathyroid glands. Immunostaining for TC of the lungs of all infants with the Di George syndrome and control infants revealed similar numbers of thyrocalcitonin-containing cells in both groups. Asynchronous development of thyroid and lung thyrocalcitonin-containing cells in those with the Di George syndrome favors the theory that the latter develop independently of derivatives of the third through fifth visceral pouches. This study further supports a neural crest origin of the Di George anomaly and strengthens the concept that the Di George anomaly is a neurocristopathy.

Embryologic and other developmental considerations of thirty-eight possible variants of the DiGeorge anomaly

The DiGeorge anomaly (DGA) represents a polytopic developmental field defect that can be caused by a number of different chromosomal, mendelian, toxic, or metabolic factors operating in early embryonic life. If the affected field is thought to be focused on either the fourth branchial arch or the third branchial pouch, with variable cephalad or caudad extension, 38 different combinations of malformations can include DiGeorge anomalies, 24 complete and 14 partial DGA, with the constraints that the field defect must be contiguous (involvement of more than one branchial arch or pouch requires involvement of all intervening arches or pouches) and complete (all derivatives of an affected branchial arch or pouch are deficient). The types and relative frequencies of abnormalities of structures other than the thymus and parathyroid glands in these possible "subsets" of DGA are discussed, and the need for more data on their occurrence in patients diagnosed as having DGA is emphasized.

Auditory and temporal bone abnormalities in CHARGE association

CHARGE association is a recently described cluster of congenital defects including ocular coloboma, heart disease, choanal atresia, retarded development and/or CNS abnormalities, genital hypoplasia, and ear anomalies. Although congenital hearing loss has been reported in CHARGE association, no information regarding the underlying temporal bone disease is available in the literature to date. The authors evaluated four patients with multiple anomalies consistent with CHARGE syndrome. Two surviving patients have bilateral severe hearing loss on auditory brain stem response testing. Two patients did not survive, and their temporal bones were obtained at autopsy for histologic examination. All four temporal bones showed severe middle ear defects including ossicular deformities, absence of the stapedius muscle, absence of the oval window, aberrant course of the facial nerve, and dehiscence of the facial nerve canal. In the more severely affected case, a Mondini-type malformation of the cochlea was present, together with multiple anomalies of the vestibular apparatus. Vestibular defects also occurred in the other case; however, the cochleae were found to be normally developed.

Cardiovascular anomalies in DiGeorge syndrome and importance of neural crest as a possible pathogenetic factor

One hundred sixty-one cases of DiGeorge syndrome (111 previously reported in which details concerning individual patients were given and 50 observed) were analyzed for occurrence and type of cardiovascular anomalies. Only 5 patients had a normal heart. Interrupted aortic arch type B was the major anomaly in 48 patients and persistent truncus arteriosus in 37. Therefore, in about half of the patients with DiGeorge syndrome the major anomaly was one that is rare. Conversely, of those patients with interrupted aortic arch, 68% had DiGeorge syndrome, as did 33% of all patients with truncus arteriosus. Although tetralogy of Fallot was also seen often in DiGeorge syndrome (10 patients), these cases represented less than 2% of the total number of cases of tetralogy of Fallot. Similarly, less than 1% of children with isolated ventricular septal defect or transposition of the great arteries had DiGeorge syndrome. The primary cardiovascular anomaly always involved the aortic arch system or the arterial pole of the heart. Recent studies show that neural crest cells play a crucial role in development of pharyngeal (bronchial) pouch derivatives, e.g., thymus and parathyroid glands, as well as the aortic arches and the truncoconal part of the heart. These studies and present observations support the view that DiGeorge syndrome and the associated cardiovascular anomalies are due to an abnormal developmental process involving the neural crest. Curiously, no instances of aortopulmonary septal defect or anomalous origin of a pulmonary artery from the ascending aorta (hemitruncus) have been associated with DiGeorge syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Reconstitution of T-cell deficiency by thymic hormone or thymus transplantation therapy

Correction of T-cell defects by either thymic hormone treatment or thymus transplantation has proven to be more difficult clinically than historically anticipated. Because the precise action of thymic hormones is unknown and because these hormones act upon post-thymic cells, therapeutic attempts may fail owing to lack of sufficient substrate population. Results of thymic transplantation suggest that this procedure may be best utilized for the treatment of mild T-cell defects, rather than as complete replacement treatment for severe deficiency. Future clinical trials of thymic transplantation or thymic hormone appear justified in narrowly circumscribed and well-characterized conditions.

Abnormal growth of the thyroid cartilage in the DiGeorge syndrome

Larynges from 17 patients with DiGeorge syndrome (DGS) and from 14 patients with tetralogy of Fallot (TOF) (11 non-DGS and 3 possible but unproven DGS) were dissected, measured, and compared to a control population of comparable body length. The patients with DGS and the 3 patients with TOF suspected of having DGS showed the following: small thyroid cartilages with increased anterior angle, abnormally short superior cornua, low ratio of mean superior cornual length to distance between superior cornual tips, and delayed time of maximal rate of increase in superior cornual length relative to increase in body length. The hypoplasia, delayed maximal growth rate and persistent fetal shape of the thyroid cartilage (predominantly a derivative of the fourth branchial arch) in DGS, indicates that the causative process in the syndrome affects not only the third and fourth branchial pouches, but also, by a contiguous field defect, other derivatives than great vessels of the fourth-sixth branchial arches.

Truncus arteriosus and facial dysmorphism

Facial features of infants with truncus arteriosus were photographed and reviewed. Anomalies included hypertelorism, low set ears, micrognathia, down-slanting palpebral fissures, short philtrum and small mouths. Associated cardiovascular defects were interrupted aortic arch, double aortic arch, right aortic arch and aberrant brachiocephalic vessels. Potential teratogenic factors included maternal diabetes, syphilis, alcohol ingestion, carbimazole therapy and infant chromosomal anomalies. The facial features, together with the rare cardiac abnormalities of truncus arteriosus and aortic arch defects are similar to those described in Di George syndrome (defect of fourth branchial arch and derivatives of third and fourth pharyngeal pouches). However none of these patients had symptomatic hypocalcaemia or absence of the thymus. It is concluded that this association of truncus arteriosus, aortic arch abnormalities and facial anomalies involves first and fourth branchial arch maldevelopment, and indicates embryological insult between the fourth and seventh weeks of gestation.

Short trachea, with reduced number of cartilage rings--a hitherto unrecognized feature of DiGeorge syndrome

Adequate tracheas from 6 of 14 patients with DiGeorge syndrome (2 complete and 4 partial forms) were available for tracheal ring study. The number of tracheal rings in these patients was significantly low (mean +/- SD 14.7 +/- 1.4). This is consistent with an effect of deficient blood supply to the fetal cervical region, a mechanism that has been proposed to explain the defective development of thymus and parathyroid glands in DiGeorge syndrome. To our knowledge this lesion has not been described as one of the malformations found in the syndrome. In 8 of 14 (57%) patients with DiGeorge syndrome, common origin of the carotid arteries was found, and 4 of these 8 patients showed minor tracheal compression. These findings support the proposal that abnormal blood supply to the region of the third and fourth pharyngeal arches may play a role in the pathogenesis of DiGeorge syndrome.

Familial third-fourth pharyngeal pouch syndrome with apparent autosomal dominant transmission

A family is presented in which both siblings and their father had evidence of third-fourth pharyngeal pouch syndrome (DiGeorge syndrome). All three individuals had hypocalcemia and unusual facies. Both infants had truncus arteriosus. One infant had evidence of impaired cell-mediated immunity; the father had a relatively decreased number of T-lymphocytes. The syndrome is uncommon, most cases being isolated, and familial presentations are even rarer. Two recent reports described several affected individuals who also had partial deletions of chromosome 22. Chromosome banding studies in our family were normal. Thus our family demonstrates an autosomal dominant pattern of inheritance, although it cannot be proved that this is a single gene defect. We propose that inasmuch as the presentation of the syndrome is quite varied, thorough family investigation including high-resolution cytogenetic analysis is necessary. Familial cases may be more common and require genetic counseling.

Temporal bone pathology in DiGeorge's syndrome

DiGeorge's syndrome is characterized by partial or complete absence of the parathyroid and thymus glands and is often associated with other developmental anomalies, particularly of the structures arising from the third and fourth pharyngeal pouches. The temporal bone findings in three cases of DiGeorge's syndrome are presented. Patients with this condition have a high incidence of Mondini dysplasia in both ears, sometimes with other anomalies of the external or middle ears. Hearing may range from normal to profound deafness and may manifest sensorineural, conductive, or mixed losses of varying degrees.

Abnormalities of T cell maturation and regulation in human beings with immunodeficiency disorders

A series of monoclonal antibodies to T cell surface antigens were used to characterize peripheral lymphoid populations from patients with a variety of immunodeficiency diseases. Several disorders of T cell differentiation were observed to occur in severe combined immunodeficiency. One subtype of severe combined immunodeficiency was associated with failure to develop lymphocytes that express any thymus specific antigens, another with failure to differentiate beyond the early prothymocyte-thymocyte (T9+, T10+) stage, while a third subtype was associated with failure to differentiate beyond a late thymocyte (T3+, T4+, T5+/T8+, T10+) stage. In contrast, patients with thymic aplasia (DiGeorge syndrome) had a diminished but detectable population of mature T cells. Imbalances in immunoregulatory T cells with a relative excess of suppressor cells were found in 9 of 17 patients with spontaneously occurring acquired agammaglobulinemia. In one of the latter individuals, there was an activated suppressor T cell population expressing Ia antigens (T+/T8+, Ia+). Another had no inducer T4+ cells. Patients with X-linked agammaglobulinemia frequently had an abnormal ratio of inducer to suppressor cells as well as an absence of circulating surface immunoglobulin-bearing cells. No such abnormalities were noted in normals or individuals with selective immunoglobulin (Ig)A deficiency. Taken together, these findings support the notion that several immunodeficiency states may occur as a consequence of defective T cell maturation or imbalances in immunoregulatory T lymphocyte subpopulations.

A deletion in chromosome 22 can cause DiGeorge syndrome

An association between DiGeorge's syndrome and an unbalanced chromosomal rearrangement leading to trisomy 20pter leads to 20q11 and monosomy 22pter leads to 22q11 was found in four individuals belongings to one family. These and other data from the literature are interpreted to suggest that DiGeorge's syndrome can be caused by deletion of a gene located in chromosome 22, probably in band 22q11.

Cardiovascular malformations in DiGeorge syndrome (congenital absence of hypoplasia of the thymus)

Partial or complete absence of the thymus (DiGeorge syndrome, III-IV pharyngeal pouch syndrome) is often associated with agenesis or hypoplasia of the parathyroid glands and, almost invariably, with cardiovascular malformations. The clinical and pathologcial findings in 10 cases proven at necropsy are presented. All patients presented with cardiac symptoms and signs in the first weeks of life and, with one exception, all died of a cardiac cause. Major cardiovascular malformations were found in all 10 cases. Four had, in association with a ventricular septal defect of the infundibular type, an interrupted aortic arch, which was left-sided in two and right-sided in two other cases. Four patients had truncus arteriosus type I, in two of them associated with a right-sided aortic arch. Two patients with tetralogy of Fallot had a right-sided aortic arch. Only two of the 10 had a normally developed left aortic arch. Aberrant subclavian arteries were found in five cases. From our observations and a survey of the previously published patients it appears that 90 per cent of the necropsy-proven cases of DiGeorge syndrome have cardiovascular malformations and that 95 per cent of these malformations can be classified as aortic arch anomalies, truncus ateriosus, or tetralogy of Fallot.

Thymosin therapy in the DiGeorge syndrome

Reconstruction of the T-cell immune defect in patients with the DiGeorge syndrome has been accomplished in the past by fetal thymus transplantation. Because of the risk of fatal graft-versus-host reaction with fetal thymus transplantation in patients with abnormal T-cell immunity, we have examined the effects of a thymus tissue extract, thymosin fraction 5, on the in vitro and in vivo immune function in children with the DiGeorge syndrome. T-cell numbers were increased with thymosin F5 in vitro in three of five patients. T-cell number and function was improved in three of four patients treated with thymosin F5 in vivo. Spontaneous improvement in the immune function of these patients cannot be excluded. These results suggest, however, that further trials with thymosin F5 therapy may be indicated in patients with the DiGeorge syndrome.