Congenital aplasia of the thymus gland (DiGeorge's syndrome)

Thymus transplantation for DiGeorge Syndrome: a systematic review

BACKGROUND

DiGeorge syndrome (DGS) is a condition typically associated with athymia, parathyroid hypoplasia or aplasia, and congenital heart defects. Athymia in these patients causes severe immunodeficiency, causing high mortality and morbidity, often requiring thymic tissue transplantation. The present systematic review aims to consolidate the present evidence on thymus transplantation in DGS.

METHODS

An electronic literature search of five databases (PubMed, Medline, Scopus, EBSCOhost, and CINAHL) was performed from inception till September 2024. Relevant articles were selected, and data was extracted by two independent reviewers.

RESULTS

A total of 16 articles were included from an initial set of 1227 articles. Patients diagnosed with DGS in the included studies were predominantly male, and the age at which thymus transplantation was done typically varied from 0.8 to 26 months. Several patients had chromosome 22q11 hemizygosity. Thymic tissue was taken from tissues of pediatric patients undergoing cardiothoracic surgery. Pre-transplant medication included immunosuppressants with rabbit anti-thymocyte globulin (RATGAM) being frequently used alongside steroids and tacrolimus. This tissue was cultured and transplanted into the quadriceps muscle of the patients under general anesthesia. Thymopoiesis was well described in most patients with graft failures and rejections occurring rarely. Naive T-cell development was noted in almost all patients with clearance of infections in many cases. Common postoperative complications include sepsis, haemorrhage, gastrointestinal disturbances, among others. Mortality was uncommon but often associated with intracerebral hemorrhages and sepsis.

CONCLUSION

Thymus transplantation is a relatively safe and effective procedure in patients with DGS with athymia. Future research should explore the addition of allogenic parathyroid gland transplantation along with thymic tissue.

Small fetal thymus and adverse obstetrical outcome: a systematic review and a meta-analysis

INTRODUCTION

The aim of this study was to explore the association between small fetal thymus on ultrasound and adverse obstetrical outcome.

MATERIAL AND METHODS

Medline, Embase, Cochrane and Web of Science databases were searched. Primary outcome was the risk of preterm birth before 37 and 34 weeks of gestation in fetuses with, compared to those without, a small thymus on ultrasound.

SECONDARY OUTCOMES

occurrence of chorioamnionitis, intrauterine growth restriction, neonatal sepsis, gestational age at birth, birthweight, neonatal morbidity and preeclampsia.

RESULTS

Twelve studies including 1744 fetuses who had ultrasound assessment of thymus during pregnancy were included. Women with preterm premature rupture of the membranes or with preterm labor were at higher risk of preterm birth before 37 weeks (p = 0.01), or before 34 weeks (p < 0.001) for fetuses with a small fetal thymus compared to those without a small thymus, and the risk of chorioamnionitis was higher when the thymus was small (p < 0.001). Fetuses with small thymus were not at higher risk of intrauterine growth restriction (p = 0.3). A small thymus increased the risk of neonatal sepsis (p = 0.007) and morbidity (p = 0.003), but not the risk of preeclampsia (p = 0.9).

CONCLUSIONS

A small fetal thymus is associated with a higher risk of preterm birth, chorioamnionitis, neonatal sepsis and morbidity, but not with intrauterine growth restriction and preeclampsia.

The use of imaging technology in the assessment of the fetal inflammatory response syndrome-imaging of the fetal thymus

The fetal inflammatory response syndrome (FIRS) describes a state of extensive fetal multi organ involvement during chorioamnionitis, and is associated with grave implications on perinatal outcome. The syndrome has been linked to the preterm parturition syndrome and is associated with inflammation/infection processes in most of the fetal organs. The fetal thymus, a major organ in the developing immune system involutes during severe neonatal disease and has been shown to be smaller in fetuses with FIRS. Various methods for imaging of the fetal thymus and measurement are described. Currently the only method to diagnose FIRS prenatally is through amniocentesis. We suggest that women who are admitted with preterm labor with intact membranes and those with PPROM should have a detailed sonographic examination of the fetal thymus as a surrogate marker of fetal involvement in intrauterine infection/inflammation processes.

Ethanol-induced face-brain dysmorphology patterns are correlative and exposure-stage dependent

Prenatal ethanol exposure is the leading preventable cause of congenital mental disability. Whereas a diagnosis of fetal alcohol syndrome (FAS) requires identification of a specific pattern of craniofacial dysmorphology, most individuals with behavioral and neurological sequelae of heavy prenatal ethanol exposure do not exhibit these defining facial characteristics. Here, a novel integration of MRI and dense surface modeling-based shape analysis was applied to characterize concurrent face-brain phenotypes in C57Bl/6J fetuses exposed to ethanol on gestational day (GD)7 or GD8.5. The facial phenotype resulting from ethanol exposure depended upon stage of insult and was predictive of unique patterns of corresponding brain abnormalities. Ethanol exposure on GD7 produced a constellation of dysmorphic facial features characteristic of human FAS, including severe midfacial hypoplasia, shortening of the palpebral fissures, an elongated upper lip, and deficient philtrum. In contrast, ethanol exposure on GD8.5 caused mild midfacial hypoplasia and palpebral fissure shortening, a shortened upper lip, and a preserved philtrum. These distinct, stage-specific facial phenotypes were associated with unique volumetric and shape abnormalities of the septal region, pituitary, and olfactory bulbs. By demonstrating that early prenatal ethanol exposure can cause more than one temporally-specific pattern of defects, these findings illustrate the need for an expansion of current diagnostic criteria to better capture the full range of facial and brain dysmorphology in fetal alcohol spectrum disorders.

22q11.2 deletion syndrome: genetics, neuroanatomy and cognitive/behavioral features keywords

This paper presents a conceptual review of the genetic underpinnings of 22q11.2 Deletion Syndrome. The neuroanatomical, neuropsychological, behavioral, and psychiatric phenotype associated with 22q11.2 Deletion Syndrome is also explored, including variables that are thought to affect symptom expression. The history of the deletion syndrome is described, and future directions for continued research are discussed.

Interleukin-12 receptor beta1 deficiency presenting as recurrent Salmonella infection

We describe a child with interleukin-12 receptor beta1 (IL-12Rbeta1) deficiency caused by a homozygous IL12RB1 large deletion who presented at the age of 1 year with recurrent, often asymptomatic episodes of bacteremia caused by group D Salmonella species. No mycobacterial disease or other unusual infection was present. The episodes of salmonellosis were caused by an identical serovar during a period of 18 months. This is the first case of inherited IL-12Rbeta1 deficiency diagnosed after isolated, recurrent salmonellosis.

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.

Agenesis of the corpus callosum associated with DiGeorge-velocardiofacial syndrome: a case report and review of the literature

We report a patient with clinical and cytogenetic findings consistent with DiGeorge-velocardiofacial syndrome and agenesis of the corpus callosum. This patient represents the first report of a case of DiGeorge-velocardiofacial syndrome associated with such a central nervous system abnormality. This case, together with previous reports in the literature, suggests that structural brain abnormalities, and in particular abnormalities of the corpus callosum, are part of the complex syndrome associated with the chromosomal microdeletion 22q11.2. We suggest that the diagnosis of DiGeorge-velocardiofacial syndrome be entertained in patients with agenesis of the corpus callosum in the context of other common clinical features of this syndrome.

Inflammatory response to chronic otitis media in DiGeorge syndrome: a case study using immunohistochemistry on archival temporal bone sections

Immunohistochemical analyses were conducted on archival celloidin-embedded human temporal bone sections from an 8-month-old boy with chronic otitis media and DiGeorge syndrome. We employed antigen retrieval methods with saturated sodium hydroxide-methanol solution, microwave incubation, and proteolytic treatment to demonstrate the distribution of T-lymphocytes, B-lymphocytes, macrophages, and intercellular adhesion molecule 1 (ICAM-1) expression in the middle ear. B-lymphocytes and macrophages were observed predominantly within the middle ear mucosa. T-lymphocytes were rare. Further, ICAM-1 was expressed in the vascular endothelium of the lamina propria, as well as infiltrating mononuclear cells. This suggests that the expression of ICAM-1 can be induced in the middle ear with otitis media, even if T-lymphocytes are depressed in a cell-mediated immunodeficiency disorder such as DiGeorge syndrome.

Thyroid abnormalities as a feature of DiGeorge syndrome: a patient report and review of the literature

DiGeorge syndrome or anomaly consists of a developmental field defect which is characterized by congenital absence or hypoplasia of the thymus and parathyroids, as well as facial dysmorphism and congenital heart defects. Other congenital malformations may coexist, in particular, thyroid abnormalities. A case of congenital hypothyroidism and DiGeorge syndrome is reviewed. Necropsy, clinical, and experimental studies also show that thyroid abnormalities may be a feature of DiGeorge syndrome. Although this could be purely coincidental, our case suggests that thyroid gland dysgenesis may be more common than previously thought. Thus, children with the DiGeorge syndrome may be at higher risk for hypothyroidism. Because of this potential association, patients who are considered to have this anomaly should have early newborn thyroid screening.

Hypocalcemic seizures in neonates

A case of a 2-week-old infant who presented to the emergency department (ED) with rapid eye blinking and jerking in the absence of physical abnormalities is presented. Hypocalcemia and hypomagnesemia were detected. This case represents the common presentation, therapy, and outcome of neonatal hypocalcemia. It is of particular interest to ED physicians because most of the time the etiology of neonatal seizures can be diagnosed in the ED and appropriate therapy can be immediately instituted.

Recurrent immune cytopenias in two patients with DiGeorge/velocardiofacial syndrome

We describe two patients with clinical and cytogenetic findings consistent with DiGeorge/velocardiofacial syndrome who had recurrent cytopenias at presentation. Our observations suggest that recurrent cytopenias may be part of the clinical spectrum of deletion 22q11.2. We also suggest that the diagnosis of DG/VCF syndrome be considered in patients with unexplained recurrent immune cytopenias in association with cardiac lesions, subtle craniofacial dysmorphisms, and/or learning or behavioral impairments.

Development of the thymus

Proper development of the thymus is critical for an individual to acquire full immune capability. A full complement of the components that participate in thymic development, interacting with each other at the correct time, is required for maturation. In order to establish the microenvironment necessary for T-cell differentiation, the epithelial primordium of the thymus must expand from pharyngeal endoderm with the aid of contributions from the ectoderm. Experimental studies have established the importance of mesenchymal derivatives from the neural crest in functional development of the epithelial primordium. Interfering with this process inhibits thymic development in a manner similar to that observed in congenital conditions such as the DiGeorge syndrome and the fetal alcohol syndrome. These observations provide clues to understanding the origin of defects in thymus-dependent immunity, and point the way to studies that will expand our understanding of the controls that are involved in genetic and environmental factors impacting on this process.

Abnormalities in lymphocyte populations in infants with neural crest cardiovascular defects

The DiGeorge syndrome has been associated with various immune deficits. Embryologically, defects of the neural crest are associated with conotruncal and aortic arch abnormalities. The objective of this study was to determine if children with neural crest congenital heart defects can have subtle but significant immunodeficiencies. Complete blood counts with differential counts and a standard lymphocyte immunophenotyping panel of selected monoclonal antibodies were performed on peripheral blood from 20 children with neural crest cardiac disease and 34 normal newborns. The children with cardiac disease were grouped as survivors and nonsurvivors. The mean total white blood cell count was similar for all groups, but the percent lymphocytes was significantly less in the nonsurvivors than in the survivors and normal newborns (p < 0. 02). The lymphocyte subsets affected were CD2, CD3, and CD4. When the cardiac patients were compared to the normal newborns, again differences in lymphocyte subsets CD2, CD3, and CD4 were seen. When comparing nonsurvivors with survivors, the mean percentages of the CD2, CD3, and CD4 T lymphocyte markers, as well as the mean lymphocyte, B cell (CD20), and natural killer cell (CD16) percentages were all lower in the nonsurvivors. It was concluded that abnormalities in specific lymphocyte populations and their subsets may be predictors of infants at greatest risk for immunodeficiency complications. Therefore children with neural crest cardiac defects should have evaluations of lymphocyte subsets at birth and be treated as if potentially immunodeficient.

Prenatal craniofacial development: new insights on normal and abnormal mechanisms

Technical advances are radically altering our concepts of normal prenatal craniofacial development. These include concepts of germ layer formation, the establishment of the initial head plan in the neural plate, and the manner in which head segmentation is controlled by regulatory (homeobox) gene activity in neuromeres and their derived neural crest cells. There is also a much better appreciation of ways in which new cell associations are established. For example, the associations are achieved by neural crest cells primarily through cell migration and subsequent cell interactions that regulate induction, growth, programmed cell death, etc. These interactions are mediated primarily by two groups of regulatory molecules: "growth factors" (e.g., FGF and TGF alpha) and the so-called steroid/thyroid/retinoic acid superfamily. Considerable advances have been made with respect to our understanding of the mechanisms involved in primary and secondary palate formation, such as growth, morphogenetic movements, and the fusion/merging phenomenon. Much progress has been made on the mechanisms involved in the final differentiation of skeletal tissues. Molecular genetics and animal models for human malformations are providing many insights into abnormal development. A mouse model for the fetal alcohol syndrome (FAS), a mild form of holoprosencephaly, demonstrates a mid-line anterior neural plate deficiency which leads to olfactory placodes being positioned too close to the mid-line, and other secondary changes. Work on animal models for the retinoic acid syndrome (RAS) shows that there is major involvement of neural crest cells. There is also major crest cell involvement in similar syndromes, apparently including hemifacial microsomia. Later administration of retinoic acid prematurely and excessively kills ganglionic placodal cells and leads to a malformation complex virtually identical to the Treacher Collins syndrome. Most clefts of the lip and/or palate appear to have a multifactorial etiology. Genetic variations in TGF alpha s, RAR alpha s, NADH dehydrogenase, an enzyme involved in oxidative metabolism, and cytochrome P-450, a detoxifying enzyme, have been implicated as contributing genetic factors. Cigarette smoking, with the attendant hypoxia, is a probable contributing environmental factor. It seems likely that few clefts involve single major genes. In most cases, the pathogenesis appears to involve inadequate contact and/or fusion of the facial prominences or palatal shelves. Specific mutations in genes for different FGF receptor molecules have been identified for achondroplasia and Crouzon's syndrome, and in a regulatory gene (Msx2) for one type of craniosynostosis. Poorly co-ordinated control of form and size of structures, or groups of structures (e.g., teeth and jaws), by regulatory genes should do much to explain the very frequent "mismatches" found in malocclusions and other dentofacial "deformities". Future directions for research, including possibilities for prevention, are discussed.

Prenatal craniofacial development: new insights on normal and abnormal mechanisms

Technical advances are radically altering our concepts of normal prenatal craniofacial development. These include concepts of germ layer formation, the establishment of the initial head plan in the neural plate, and the manner in which head segmentation is controlled by regulatory (homeobox) gene activity in neuromeres and their derived neural crest cells. There is also a much better appreciation of ways in which new cell associations are established. For example, the associations are achieved by neural crest cells primarily through cell migration and subsequent cell interactions that regulate induction, growth, programmed cell death, etc. These interactions are mediated primarily by two groups of regulatory molecules: "growth factors" (e.g., FGF and TGFalpha) and the so-called steroid/thyroid/retinoic acid superfamily. Considerable advances have been made with respect to our understanding of mechanisms involved in primary and secondary palate formation, such as growth, morphogenetic movements, and the fusion/merging phenomenon. Much progress has been made on the mechanisms involved in the final differentiation of skeletal tissues. Molecular genetics and animal models for human malformations are providing many insights into abnormal development. A mouse model for the fetal alcohol syndrome(FAS), a mild form of holoprosencephaly, demonstrates a mid-line anterior neural plate deficiency which leads to olfactory placodes being positioned too close to the mid-line, and other secondary changes. Work on animal models for the retinoic acid syndrome (RAS) shows that there is major involvement of neural crest cells. There is also major crest cell involvement in similar syndromes, apparently including hemifacial microsomia. Later administration of retinoic acid prematurely and excessively kills ganglionic placodal cells and leads to a malformation complex virtually identical to the Treacher Collins syndrome. Most clefts of the lip and/or palate appear to have a multifactorial etiology. Genetic variations in TGF alpha s, RAR alpha s, NADH dehydrogenase, an enzyme involved in oxidative metabolism, and cytochrome P-450, a detoxifying enzyme, have been implicated as contributing genetic factors. Cigarette smoking, with the attendant hypoxia, is a probable contributing environmental factor. It seems likely that few clefts involve single major genes. In most cases, the pathogenesis appears to involve inadequate contact and/or fusion of the facial prominences or palatal shelves. Specific mutations in genes for different FGF receptor molecules have been identified for achondroplasia and Crouzon's syndrome, and in a regulatory gene (Msx2) for one type of craniosynostosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Orofacial manifestations in the primary immunodeficiency disorders

Primary immunodeficiencies are increasingly recognized yet there is little data concerning the oral manifestations of such disorders. This article reviews the current literature and details the oral aspects of well-characterized primary immunodeficiencies.

Immune system of the spontaneously hypertensive rat: II. Morphology and function

The spontaneously hypertensive rat (SHR) is a stress-sensitive animal which exhibits moderate immune dysfunction that has been implicated in the onset of hypertension. In this study, we examined the morphology of SHR thymus and spleen and further characterized the immune deficiency using Wistar-Kyoto (WKY) and Fisher 344 (F-344) rats for comparison. The adult SHR thymus does not display the increase in medullary volume typically noted with aging and the volume density of the marginal zone is decreased in the spleen. In vivo tritiated-thymidine incorporation is also decreased in the spleen of unstimulated SHR. In mixed lymphocyte reactions (MLR), the proliferative response of SHR splenocytes is significantly decreased relative to controls, WKY and F-344. Addition of interleukin-1 (IL-1), interleukin-2 (IL-2), or indomethacin to the MLR cultures does not increase proliferation. The proliferative response to T cell receptor monoclonal antibody (mAb-TCR) or interleukin-2 (IL-2) are similarly impaired in the SHR. The depressed proliferative T cell response is reversed by prolactin. It is suggested that the SHR is a valuable model for the study of immune deficiency.

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.

Velo-cardio-facial syndrome: a review of 120 patients

A series of earlier reports has described the velo-cardio-facial syndrome (VCFS), a syndrome of multiple anomalies including cleft palate, heart malformations, facial characteristics, and learning disabilities. The patients reported previously were primarily ascertained from a craniofacial program at a large tertiary medical center. Recent reports, including a companion paper in this issue, suggest that this common syndrome of clefting is also a common syndrome of congenital heart defect (CHD) which is expressed as familial examples of DiGeorge sequence. Appreciation of more severely affected cases of VCFS and the detection of mild expressions have led to a broadening of the phenotypic spectrum of the syndrome. The purpose of this report is to describe the full spectrum of VCFS, including several new manifestations and to compare the VCFS phenotype with published cases of "familial DiGeorge sequence" which are now thought to represent examples of VCFS.

Anomalous right coronary artery associated with sudden death: an example of a neural crest migration defect

A unique right coronary artery anomaly of hemodynamic significance was discovered in a young adult who suddenly died. In addition, abnormally migrated, or supernumerary, thymic tissue with embedded parathyroid glands was present. This combination of congenital malformations suggests that the pathogenesis of this rare cardiac anomaly may be explained by a cranial neural crest defect.

Capacity of neural crest cells from various axial levels to participate in thymic development

In order to assess the capacity of neural crest from different sources to participate in thymic development, neural crest from selected axial levels was transplanted unilaterally from quail donors to the region in chick hosts from which neural crest cells normally migrate to interact with the primordial thymus. The greatest representation of donor cells was observed after isotopic transplantation and when donor tissue was taken from the hyoid and mesencephalic regions of the neural crest. The capacity for transplants to contribute cells decreased both anteriorly and posteriorly, so that neural crest close to the usual origin of mesenchyme-producing cells contributed a large number of donor cells around the developing thymus than neural crest from anterior and posterior regions. Cells from the transplant were inserted as an addition to the host chick cells. Thus, a special relationship and capacity for interaction in thymic development is expressed by neural crest at usual levels over a limited span of axial regions, but to some extent by all regions. This study has established that the capacity for neural crest cells from different axial levels to interact with developing organs is not uniform, but may vary, depending upon the nature of the interaction with a particular organ.

Alteration of early vascular development after ablation of cranial neural crest

A previous study has shown that, subsequent to ablation of cranial neural crest, heart morphology and pharyngeal arch vessels (aortic arches) are altered before septation of the outflow tract normally occurs. In the present study, we concentrated on very early development of the aortic arch apparatus in the chick (incubation days 3-5). The three-dimensional organization of the arch vessel apparatus was studied by scanning electron microscopy after intravascular injection of Mercox, and by serial sections of embryos embedded in plastic. Alterations in the arch vessel apparatus were already present by day three in embryos with neural crest ablation at stage 9-10. Bilateral symmetry frequently was lost. Arch vessels sometimes were enlarged and occupied most of the arch, with little surrounding mesenchyme. Some arch vessels were small or occluded. Mesenchyme was significantly reduced in quantity in the arches, and was not condensed and symmetrical as in controls. There was a significant increase in the proportion of direct apposition of vessel endothelium with epithelium, without the intervening mesenchyme typical of controls. The surgical manipulation used in this study leads to distinct alterations in the arches of components and relationships which are important in development. Altered blood flow likely affects the development of the heart.

Neural crest ablation does not alter pulmonary vein development in the chick embryo

Cranial neural crest, which extends from the mid-diencephalon to somite five, plays an integral role in development of pharyngeal arch derivatives and supplies mesenchyme to the aortic arch arteries. Neural crest cells in pharyngeal arches three, four, and six migrate to the heart and are involved in aorticopulmonary and conotruncal septation. Ablation of the "cardiac" neural crest cells in chick embryos results in a variety of outflow tract anomalies, including persistent truncus arteriosus. Although other studies have shown the importance of the neural crest in the development of the cardiac outflow tract, the role of neural crest in venous development has not been established. This investigation evaluates the effect of cardiac neural crest ablation on the morphological development of the pulmonary vein. The presence of the pulmonary vein was confirmed initially at early stage 15 using histological sections and computer reconstructions of serially sectioned, normal embryos. India ink injections demonstrated a complete, patent pulmonary circuit at stage 18. Cardiac neural crest was ablated at stages 8-10. Operated, sham-operated, and control embryos were sacrificed at incubation day 11, and acrylic plastic casts prepared of the intravascular compartment. In experimental embryos with persistent truncus arteriosus, there were no morphological differences in the pulmonary veins, compared with shams and controls. These data indicate that the lesions of the cardiac neural crest have little morphological impact on pulmonary vein development. It is concluded that alterations in the cardiac neural crest are not involved in venous anomalies such as cor triatriatum and total or partial anomalous pulmonary venous return.

Facial and immunological anomalies associated with tetralogy of Fallot

Dysmorphic facial features were present in 9 of 31 children with tetralogy of Fallot anatomy (29%). These anomalies included hypertelorism, low-set ears, small mouth, short philtrum, and micrognathia. Ten children had pulmonary atresia, 13 (42%) had a right aortic arch, and 13 had extracardiac congenital anomalies. There were 16 children in the series (52%) who had hospital admissions for important or recurrent infections, and 18 who had immune deficiency: low levels of T lymphocytes were found in 9, low levels of complement in 8, and low immunoglobulins in 3. Embryologically, the cardiac outflow tracts, the aortic arch, the face, and the thymus develop at the same time, and all receive migrating cells from the neural crest. Teratogenic factors possibly produce this constellation of anomalies, which is in the spectrum of the Di George syndrome (third and fourth pharyngeal pouch syndrome). It is of importance for the management of such children, that their immune deficiency be recognized and treated appropriately.

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.

Effect of neural crest ablation on development of the heart and arch arteries in the chick

Mesenchymal derivatives of the neural crest contribute to the connective tissues and blood vessels of the pharyngeal arches, and participate in the septation of the outflow tract of the heart. The present study was designed to determine the nature and timing of alterations in the development of the heart and arch arteries subsequent to diminished neural crest contributions. The neural crest contributing to the three caudalmost pharyngeal arches was ablated bilaterally in chick embryos and compared with sham or unoperated controls. Heart development was studied by scanning electron microscopy. Arch artery development was studied microscopically after intravascular injection of India ink and clearing of the specimen. Neural crest ablation caused morphological changes in most hearts. Hearts in experimental animals commonly were elongate and were subject to inappropriate development of ventricular and atrial areas. A surgical effect delayed the disappearance of arch arteries one and two, and removal of neural crest produced an additional delay. Neural crest ablation caused failure of arch arteries three, four (right), and six to develop to the proper size in some animals. Survival of those whose sixth arch arteries achieved the proper size caused group measurements to reach normal values again by stage 32. Closure of arch arteries in some animals and maintenance in others produced greater variability in experimental animals than in controls. It is significant that heart morphology was altered before septation of the outflow tract normally occurs. This indicates at the least that another factor, such as altered blood flow, contributes to the abnormal development. Altered flow may result from changes in pharyngeal arch mesenchyme and arch artery endothelium.

Hypoparathyroidism in Arab children

Four children with hypoparathyroidism are reported. We believe that this is the first report of this condition from Kuwait or Saudi Arabia. Treatment and course of disease are discussed. Two children have hypoparathyroidism as part of DiGeorge Syndrome.

Abnormal heart and great vessel development following acute ethanol exposure in mice

Two maternal intraperitoneal doses of ethanol (2.9 g/kg) administered on gestational day (GD) 8, 12 hours (8 d, 12 h) and 8 d, 16 h result in abnormal heart and great vessel development in C57B1/6J mice. Heparinized hearts from GD 9 to 18 conceptuses were dissected to expose the forming or already completed ventricular septum and great vessels and then routinely processed for scanning electron microscopy. As early as GD 9 (12 hours post-treatment), size deficiency and abnormal external contour of the cardiac tube were notable. By GD 12, deficiencies in the size of the conal and atrioventricular (A-V) endocardial cushions, as well as abnormal positioning of the A-V canal, were demonstrable. On GD 13, when the ventricular septum should be complete, a range of deficiencies in the conal tissue was observed. Deficiencies observed were a lack of closure of the ventricular septum in the region of the membranous septum, and lack of septation of the conal portion of the developing heart. These deficiencies persist and have been documented through GD 18. Other abnormalities noted on GD 18 include double-outlet right ventricle, as well as distal defects of the great vessels including interrupted aortic arch, right aortic arch, and a vascular ring. While these defects are comparable to those seen in the fetal alcohol syndrome, they also overlap considerably with cardiac defects that are characteristic of those in the DiGeorge Syndrome as well as in the CHARGE Association. Recent work by others as well as the fact that acute ethanol exposure in this animal model corresponds to a time of neural crest cell migration has led to the speculation that this cell population is involved in the cardiovascular pathogenesis described.

The DiGeorge anomaly as a developmental field defect

The DiGeorge "syndrome" is a characteristic malformation pattern involving craniofacial, cardiac, thymic, and parathyroid structures. Evidence is accumulating that the DiGeorge "syndrome" is actually not a syndrome, but a polytopic developmental field defect. We present evidence of causal heterogeneity of the DiGeorge anomaly. This heterogeneity will be discussed in the light of recent findings that indicate that the dysmorphogenetically reactive unit responsible for the phenotype of the DiGeorge anomaly is a population of cephalic neural crest cells.

Fetal alcohol syndrome and DiGeorge anomaly: critical ethanol exposure periods for craniofacial malformations as illustrated in an animal model

Acute maternal ethanl (alcohol) administration induces different craniofacial anomalies in the offspring of experimental animals, depending on the gestational day of teratogen exposure. Previous studies in our laboratories have illustrated the sequence of developmental changes leading to the "typical" fetal alcohol syndrome (FAS) craniofacial phenotype which results from teratogen exposure during gastrulation. These facial features are accompanied by deficiencies in median forebrain derivatives. Ethanol teratogenesis at this time apparently results in a loss of midline territory of the embryonic disc with little effects on neural crest-dependent laterally derived structures including the visceral arches. Acute ethanol exposure in mice 1 1/2 days later, at a time when neural crest cells are populating the frontonasal prominence and the visceral arches, results in a craniofacial phenotype that is similar to that noted in the DiGeorge anomaly or sequence. Sequential scanning electron microscopic analysis in our laboratory of embryos exposed on day 8 1/2 have illustrated deficiencies in the developing facial prominences and the visceral arches. The developing forebrain and midbrain appear hypoplastic. We have also observed heart, great vessel, and thymus abnormalities in these fetuses. Histologic analyses indicate that a common pathogenetic basis for the above-mentioned (day 8 1/2-induced) fetal alcohol effects appears to be an interference with the integrity of the cranial (including occipital) neural crest. Other discrete cell populations may also be involved since we have observed abnormalities in other regions, including placodal and closing membrane tissues. This animal model provides evidence linking maternal ethanol abuse during the 3rd or 4th weeks of human gestation to the development in the conceptus of FAS or DiGeorge anomally craniofacial characteristics, respectively. As the DiGeorge anomaly has been noted in the offspring of alcoholic women, this animal model indicates that ethanol and/or its metabolites is, in these cases, the causative agent.

Pathologic features of the CHARGE association: support for involvement of the neural crest

Defects associated with choanal atresia include coloboma, cardiac anomalies (usually involving the conotruncal region), physical or mental retardation, genital hypoplasia, and abnormalities of the ear. This constellation of defects is known as the "CHARGE" association and may be accompanied by other anomalies. Many of these defects seem to result from abnormalities in the development, migration, or interaction of cells of the cephalic neural crest. The range of variation in neural crest development is substantial, as indicated by the rather large number of malformation complexes and syndromes that are related phenotypically to the CHARGE association. The increasingly unwieldy nature of this collection of malformations demonstrates the need for an expanded classification of the "neurocrestopathies."

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.

Immuno-reconstitution by thymic transplant in DiGeorge's syndrome

Persistent hypocalcaemic tetany in a breast-fed neonate made us suspect DiGeorge's syndrome, particularly as the baby had an abnormal facies, and a ventricular septal defect. Immuno-reconstitution was successfully achieved by thymic transplant. Evidence of immuno-reconstitution on the basis of the histology of the post-transplant thymus has not been previously recorded.

Neural crest and normal development: a new perspective

Several clinical syndromes, including the DiGeorge syndrome, are characterized by clusters of developmental defects of the heart and great vessels with structures derived from the embryonic pharyngeal apparatus including thymus and parathyroids. The connective tissue derivatives of neural crest are necessary for the normal development of these structures, and there is new experimental evidence that depletion of neural crest causes defects similar to these clinical syndromes. Therefore it is proposed that many of these syndromes are due to inappropriate development of neural crest. The implications of this hypothesis include the predictions 1) that asplenia and certain other anomalies have the same etiology, and 2) that it is possible to observe the effects of teratogenic agents upon a cellular population (neural crest) at the time when it is being altered, rather than waiting until definitive organs may be examined.

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.

Dependence of thymus development on derivatives of the neural crest

Elimination of limited areas of the cephalic neural crest in stage 9 or 10 chick embryos markedly reduced the size of the thymus gland or resulted in its absence. Small thymic lobes contained both thymocytes and epithelial cells but showed delayed development. Parathyroid and thyroid glands sometimes were reduced in size or missing from the normal location on one or both sides. Heart defects were consistently present. Thymus development may depend on direct interaction of mesenchymal derivatives of the neural crest with pharyngeal epithelium. Multiple defects, such as the Di George syndrome, may result from failure of neural crest derivatives to migrate and interact properly.

Oral findings in DiGeorge syndrome

An 8-year-old female with DiGeorge syndrome was referred for dental treatment. Previous medical examination had disclosed heart and aortic arch malformations, hypoparathyroidism and an impaired cellular immune response. At dental examination, hypertelorism, a short philtrum, low-set malformed ears, a cleft palate and severe enamel hypoplasia were noted. The chronological distribution of enamel defects corresponded to the patients' age at known episodes of profound hypocalcemia occurring during treatment with vitamin D. Branchial dysembryogenesis should be considered in any case with dental changes related to hypoparathyroidism.

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.

Anti-ovarian and anti-lymphocyte antibodies in patients with chronic vaginal candidiasis

Seventeen of 30 patients with chronic vaginal candidiasis (CVC) of at least 5 years duration had varying degrees of menstrual problems and defective T lymphocyte function; 8 developed amenorrhea. In a group of 40 CVC patients, titers of autoantibodies to ovary, thymocytes, a T-cell line (CCRF-CEM), and a B-cell line (RN114) were significantly higher than those in 45 normal females (69 +/- 3 vs. 5 +/- 2, 70 +/- 27 vs. 4 +/- 2, l7 +/- 6, vs. 4 +/ 2, and 73 +/- 24 vs. 8 +/- 5, respectively, mean +/- S.E.). Antibody titers to sperm, T-cell line HSB-2, and B-cell lines RAJI and BALL-1 were within the normal range. Significant correlations were found between anti-Candida, anti-ovarian, and anti-thymocyte antibody titers. Similar results were found for 6 patients with chronic mucocutaneous candidiasis (CMCC) and in serial samples obtained over a one-year period from a representative patient with both CVC and CMCC. The anti-T-lymphocyte antibodies in these patients were directed primarily against non-suppressor (predominately helper) T cells. Absorption of the sera with either Candida cells, ovarian follicle cells, or thymocytes reduced all three antibody titers; absorption with sperm or B-cell lines did not alter the titers. These results suggest the presence of one or more cross-reactive antigens on ovarian follicle, T lymphocytes (especially the helper cell subpopulation), and Candida.

An evolution of therapy for mucocutaneous candidiasis

Chronic mucocutaneous candidiasis is a relatively uncommon form of candida infection, and can be found in patients with primary deficiencies of their immune systems. When such infection occurs in patients with non-lethal immune deficiences defects of chemotaxis or cellular immunity can be found. In addition, significant endocrinopathies may occur, particularly involving the parathyroid and adrenal glands. A number of therapies have been devised for the treatment of chronic candidiasis, and have included both local and systemic medications. The most useful of these in the past have included the polyene antibiotics -- most notably, nystatin and amphotericin B. Antifungal activity has also been demonstrated clinically with the use of 5-fluorocytosine (a fluorinated pyramidine) and clotrimazole (a synthetic imidazole derivative). However, long-term therapy with medication has been required, and re-emergence of symptomatic infection has occurred when medications have been stopped. More recently, immune reconstitution with transfer factor has been employed in the treatment of patients who have been found to be anergic to candida. Such treatment in conjunction with chemotherapy has indicated that effective patient remissions can be obtained in those patients who develop and maintain cell-mediated immunity to candida. Twelve patients with chronic mucocutaneous candidiasis are profiled. Sites of involvement in the head and neck included the skin and hair (9), ears (9), nose (4) and throat (12). One patient had candida laryngitis, while five patients had evidence for esophageal disease. Of this latter group, one (a 5-year old boy) developed esophageal stenosis which required gastrostomy and retrograde esophageal dilatations. Nine patients were found to be anergic to candida. In these patients, systemic chemotherapy (as amphotericin B or 5-fluorocytosine) was used to induce remissions of disease and transfer factor was given to induce reactivity to candida. By so doing, topical or oral medications (utilizing miconazole, clotrimazole and nystatin) were found to suffice in maintaining effective local control of infection.