The DiGeorge sequence. II. Immunologic findings in partial and complete forms of the disorder

Case report: Effectiveness of sirolimus in treating partial DiGeorge Syndrome with Autoimmune Lymphoproliferative Syndrome (ALPS)-like features

BACKGROUND

DiGeorge Syndrome (DGS) is a rare disease associated with 22q11.2 chromosomal microdeletion, also known as a velocardiofacial syndrome, based on the frequent involvements of the palate, facial, and heart problems. Hematologic autoimmunity is rare in DGS but presents with a refractory course and poor prognosis. Herein, we report a case of partial DGS in a patient with refractory immune cytopenia and autoimmune lymphoproliferative syndrome (ALPS)-like manifestations.

CASE DESCRIPTION

A 10-year-old boy with growth retardation presented initially with a ventricular septal defect at 7 months old, which had been repaired soon after. The patient suffered from thrombocytopenia and progressed into chronic refractory immune thrombocytopenia (ITP) at 30 months old. One year later, the patient developed multilineage cytopenias including thrombocytopenia, neutropenia, and anemia. First-line treatment of ITP, like high-dose dexamethasone and intravenous immunoglobulin, had little or short-term effect on controlling symptoms. Whole-exome sequencing revealed the presence of a de novo heterozygous 2.520 Mb deletion on chromosome 22q11.21. Moreover, decreased proportion of naive T cells and elevated double-negative T cells were found. The patient was given sirolimus therapy (1.5 mg/m², actual blood concentration range: 4.0-5.2 ng/ml) without adding other immunosuppressive agents. The whole blood cell count was gradually restored after a month, and the disease severity was soothed with less frequency of infections and bleeding events. Decreased spleen size and restrained lymph node expansion were achieved after 3-month sirolimus monotherapy.

CONCLUSIONS

This case is the first description on the efficacy of sirolimus monotherapy to treat refractory multilineage cytopenias of DGS presented with ALPS-like features.

Reduction of CRKL expression in patients with partial DiGeorge syndrome is associated with impairment of T-cell functions

BACKGROUND

Partial DiGeorge syndrome (pDGS) is caused by deletion of the 22q11.2 region. Within this region lies CrK-like (CRKL), a gene encoding an adapter protein belonging to the Crk family that is involved in the signaling cascade of IL-2, stromal cell-derived factor 1α, and type I interferon. Although recurrent infections can be observed in patients with deletion of chromosome 22 syndrome, the immune pathogenesis of this condition is yet not fully understood.

OBJECTIVE

We aimed to investigate the role of CRKL in T-cell functional responses in patients affected with pDGS.

METHODS

Protein expression levels and phosphorylation of CRKL were evaluated in patients with pDGS. T-cell functional assays in vitro and gene-silencing experiments were also performed.

RESULTS

CRKL protein expression, as well as its phosphorylation, were reduced in all patients with pDGS, especially on IL-2 stimulation. Moreover, T cells presented impaired proliferation and reduced IL-2 production on anti-CD3/CD28 stimulation and decreased c-Fos expression. Finally, CRKL silencing in Jurkat T cells resulted in impaired T-cell proliferation and reduced c-Fos expression.

CONCLUSIONS

The impaired T-cell proliferation and reduction of CRKL, phosphorylated CRKL, and c-Fos levels suggest a possible role of CRKL in functional deficiencies of T cells in patients with pDGS.

Case report: two patients with partial DiGeorge syndrome presenting with attention disorder and learning difficulties

DiGeorge syndrome (DGS) has classically been characterized by the triad of clinical features including congenital cardiac defects, immune deficiencies secondary to aplasia or hypoplasia of the thymus, and hypocalcaemia due to small or absent parathyroid glands. The phenotypic features of these patients are much more variable and extensive than previously recognized. The acknowledgement of similarities and phenotypic overlap of DGS with other disorders associated with genetic defects in 22q11 has led to an expanded description of the phenotypic features of DGS including palatal/speech abnormalities, as well as cognitive, neurological and psychiatric disorders. Here, we report the cases of two DGS patients with dysmorphic facial features who were initially admitted to the Psychiatry Department for attention disorder and learning difficulties.

Secondary immunologic consequences in chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome)

Clinical evidence suggests that patients with Chromosome 22q11.2 deletion (Ch22q11.2D) have an increased prevalence of atopic and autoimmune disease and this has been without explanation. We hypothesized that the increase in atopy was due to homeostatic proliferation of T cells leading to a Th2 skew. We performed intracellular cytokine staining to define Th1/Th2 phenotypes in toddlers (early homeostatic proliferation) and adults (post homeostatic proliferation) with this syndrome. To attempt to understand the predisposition to autoimmunity we performed immunophenotyping analyses to define Th17 cells and B cell subsets. Adult Ch22q11.2D patients had a higher percentage of IL-4+CD4+ T cells than controls. Th17 cells were no different in patients and controls. In addition, adult Ch22q11.2D syndrome patients had significantly lower switched memory B cells, suggesting a dysregulated B cell compartment. These studies demonstrate that the decrement in T cell production has secondary consequences in the immune system, which could mold the patients' clinical picture.

Immune constitution monitoring after PBMC transplantation in complete DiGeorge syndrome: an eight-year follow-up

A young boy with a confirmed complete DiGeorge Syndrome (cDGS) underwent a peripheral blood mononuclear cell transplantation (PBMCT) from his HLA-identical sister at 4.5 years of age, without a conditioning regimen. Eight years later, he is healthy with good immunological functions in the presence of a stable mixed T-cell chimerism. Absence of recent thymic emigrants is confirmed. We observe an inverted CD4+/CD8+ ratio, related to the CD8 subset expansion, a skewing of the TCR repertoire, especially on the CD8+ subset and a telomere loss on the CD8+ cells compared to the donor. However, these anomalies do not seem to have an impact on functional immunity. PBMCT in cDGS using an HLA-matched sibling donor provides good long-lasting immunity and is an easy alternative to bone marrow transplantation and to thymic transplantation.

Humoral immune responses and CD27+ B cells in children with DiGeorge syndrome (22q11.2 deletion syndrome)

The spectrum of T-cell abnormalities in 22q11.2 syndrome is quite broad, ranging from profound and life threatening to non-existent defects. Humoral abnormalities have been described in some of these patients, although no data are currently available on their phenotypical and functional B cell subsets. The purpose of this study was to investigate humoral immune function in a cohort of 13 children with DiGeorge syndrome by immunophenotyping B and by analysing their functionality in vivo. Humoral immunity was assessed by serum immunoglobulin evaluation, IgG subclasses determination, and testing of specific antibody titers to recall antigens. B cells were analyzed by flow cytometry and the relevant percentage of membrane surface expression of CD27, IgM, IgD was evaluated. In our cohort, one of 13 children (7.7%) had a complete IgA deficiency, four of 13 (30.7%) had minor immunoglobulin abnormalities, and five (38%) had an impaired production of specific antibodies. Five of 13 children (38%) had recurrent infections. Interestingly, peripheral CD27+ B cells were reduced in our patients as compared with age-matched healthy controls, and this decrement was statistically significant for IgM+ IgD+ CD27+ B cells. Immunoglobulin abnormalities were associated with the occurrence of recurrent infections. We conclude that a significant proportion of patients with DiGeorge syndrome have defective humoral immunity, which may represent an additional pathogenic mechanism underlying the increased susceptibility to infections. Whether the decreased CD27+ B-cell subset might be one of the defects that contribute to impaired humoral immunity, and to susceptibility to infection remains to be elucidated.

Complete DiGeorge anomaly in the absence of neonatal hypocalcemia and velofacial and cardiac defects

We report an atypical case of complete DiGeorge (DG) anomaly that presented initially exclusively as severe combined immunodeficiency (SCID). The child had severe infections at diagnosis, in keeping with the SCID phenotype; however, normal lymphocyte counts and immunoglobulin levels were noted at admission, which delayed diagnosis. Importantly, the child presented without neonatal hypocalcemia or velofacial or cardiac abnormalities at the time of diagnosis, which masked underlying DG. This case outlines the difficulties in making the diagnosis of SCID in a timely manner and illustrates the variation in presentation of the 22q11.2 deletion syndrome. There should be a high index of suspicion for primary immunodeficiency among children with severe infections and, because management may vary, DG anomaly should be considered in the differential diagnosis of T- B+ natural killer+ SCID.

Thymic transplantation for complete DiGeorge syndrome: medical and surgical considerations

BACKGROUND/PURPOSE

Complete DiGeorge syndrome results in the absence of functional T cells. Our program supports the transplantation of allogeneic thymic tissue in infants with DiGeorge syndrome to reconstitute immune function. This study reviews the multidisciplinary care of these complex infants.

METHODS

From 1991 to 2001, the authors evaluated 16 infants with complete DiGeorge syndrome. All infants received multidisciplinary medical and surgical support. Clinical records for the group were reviewed.

RESULTS

Four infants died without receiving a thymic transplantation, and 12 children survived to transplantation. The mean age at time of transplantation was 2.7 months (range, 1.1 to 4.4 months). All 16 infants had significant comorbidity including congenital heart disease (16 of 16), hypocalcemia (14 of 16), gastroesophageal reflux disease or aspiration (13 of 16), CHARGE complex (4 of 16), and other organ involvement (14 of 16). Nontransplant surgical procedures included central line placement (15 of 16), fundoplication or gastrostomy (10 of 16), cardiac repair (10 of 16), bronchoscopy or tracheostomy (6 of 16), and other procedures (12 of 16). Complications were substantial, and 5 of the 12 transplanted infants died of nontransplant-related conditions. All surviving infants have immune reconstitution, with follow-up from 2 to 10 years.

CONCLUSIONS

Although the transplantation of thymic tissue can restore immune function in infants with complete DiGeorge syndrome, these children have substantial comorbidity. Care of these children requires coordinated multidisciplinary support.

Otolaryngologic manifestations of immunodeficiency

Otolaryngologists are frequently consulted to manage infectious and noninfectious complications of immune deficiency. Although defects of host defense and recurrent or severe infections are the most obvious manifestations of immune deficiency, patients are often at increased risk for autoimmune and malignant disease as well. Knowledge of primary and acquired immune deficiencies will facilitate appropriate identification, treatment, and referral of patients with these defects. When immunodeficiency is known or suspected, it is particularly important to have a high index of suspicion for unusual or severe manifestations of infection, to have a low threshold for obtaining imaging to aid in diagnosis, and to treat infections for longer periods of time with higher doses of antibiotic. Surgery may be required for definitive treatment of infections that do not respond to medical therapy and for management of complications of infectious disease

Thymus transplantation in complete DiGeorge syndrome: immunologic and safety evaluations in 12 patients

Complete DiGeorge syndrome is a fatal condition in which infants have no detectable thymus function. The optimal treatment for the immune deficiency of complete DiGeorge syndrome has not been determined. Safety and efficacy of thymus transplantation were evaluated in 12 infants with complete DiGeorge syndrome who had less than 20-fold proliferative responses to phytohemagglutinin. All but one had fewer than 50 T cells/mm3. Allogeneic postnatal cultured thymus tissue was transplanted. T-cell development was followed by flow cytometry, lymphocyte proliferation assays, and T-cell receptor Vbeta (TCRBV) repertoire evaluation. Of the 12 patients, 7 are at home 15 months to 8.5 years after transplantation. All 7 survivors developed T-cell proliferative responses to mitogens of more than 100 000 counts per minute (cpm). By one year after transplantation, 6 of 7 patients developed antigen-specific proliferative responses. The TCRBV repertoire showed initial oligoclonality that progressed to polyclonality within a year. B-cell function developed in all 3 patients tested after 2 years. Deaths were associated with underlying congenital problems. Risk factors for death included tracheostomy, long-term mechanical ventilation, and cytomegalovirus infection. Adverse events in the first 3 months after transplantation included eosinophilia, rash, lymphadenopathy, development of CD4-CD8- peripheral T cells, elevated serum immunoglobulin E (IgE), and possible pulmonary inflammation. Adverse events related to the immune system occurring more than 3 months after transplantation included thrombocytopenia in one patient and hypothyroidism and alopecia in one other patient. Thymic transplantation is efficacious, well tolerated, and should be considered as treatment for infants with complete DiGeorge syndrome.

Biased T-cell receptor repertoires in patients with chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome)

Chromosome 22q11.2 deletion (del22q11.2) syndrome (DiGeorge syndrome/velocardiofacial syndrome) is a common syndrome typically consisting of congenital heart disease, hypoparathyroidism, developmental delay and immunodeficiency. Although a broad range of immunologic defects have been described in these patients, limited information is currently available on the diversity of the T-cell receptor (TCR) variable beta (BV) chain repertoire. The TCRBV repertoires of nine patients with del22q11.2 syndrome were determined by flow cytometry, fragment size analysis of the third complementarity determining region (CDR3 spectratyping) and sequencing of V(D)J regions. The rate of thymic output and the phenotype and function of peripheral T cells were also studied. Expanded TCRBV families were detected by flow cytometry in both CD4+ and CD8+ T cells. A decreased diversity of TCR repertoires was also demonstrated by CDR3 spectratyping, showing altered CDR3 profiles in the majority of TCRBV families investigated. The oligoclonal nature of abnormal peaks detected by CDR3 spectratyping was confirmed by the sequence analysis of the V(D)J regions. Thymic output, evaluated by measuring TCR rearrangement excision circles (TRECs), was significantly decreased in comparison with age-matched controls. Finally, a significant up-regulation in the percentage, but not in the absolute count, of activated CD4+ T cells (CD95+, CCR5+, HLA-DR+), IFN-gamma - and IL-2-expressing T cells was detected. These findings suggest that the diversity of CD4 and CD8 TCRBV repertoires is decreased in patients with del22q11.2 syndrome, possibly as a result of either impaired thymic function and/or increased T-cell activation.

T-cell immune constitution after peripheral blood mononuclear cell transplantation in complete DiGeorge syndrome

Complete DiGeorge syndrome (cDGS) is a congenital disorder characterized by typical facies, thymic aplasia, susceptibility to infections, hypoparathyroidism and conotruncal cardiac defect. Fetal thymus or post-natal thymus tissue transplantations and human leucocyte antigen (HLA)-genoidentical bone marrow transplantations were followed in a few cases by immune reconstitution. More recently, a peripheral blood mononuclear cell transplantation (PBMCT) was performed with an HLA-genoidentical donor and followed by a partial T-cell engraftment and immune reconstitution. We report a boy with cDGS, without cardiac defect, who suffered recurrent severe infections. At the age of 4 years, he underwent PBMCT from his HLA-genoidentical sister. He received no conditioning regimen, but graft-versus-host disease (GVHD) prophylaxis was with oral cyclosporin A and mycophenolate mofetil. Toxicity was mild, with grade I acute GVHD. The patient is currently 2.5 years post-PBMCT with excellent clinical performances. Mixed chimaerism can only be observed on the T-cell population (50% donor T cells). T-lymphocyte count fluctuated (CD3 more than 400 x 10(6)/l at d 84 and CD4 more than 200 x 10(6)/l at d 46). Exclusive memory phenotype T cells and absence of new thymic emigrants suggest expansion of infused T cells. T-cell mitogen and tetanus antigen responses normalized a few months after transplantation. After immunizations, specific antibodies were produced. PBMCT from an HLA identical sibling could be an efficient treatment of immune deficiency in cDGS.

DiGeorge syndrome/chromosome 22q11.2 deletion syndrome

DiGeorge syndrome is characterized by conotruncal cardiac defects, hypocalcemia, and a hypoplastic thymus. Many, but not all, patients have a heterozygous deletion of chromosome 22q11.2. In its most severe form, it represents a devastating syndrome with high mortality. Patients with severe immunodeficiency are candidates for a thymic transplant or a fully matched bone marrow transplant. Fortunately, the majority of patients with either DiGeorge syndrome or chromosome 22q11.2 deletion syndrome have a mild to moderate immunodeficiency. These patients may develop recurrent infections or autoimmune disease.

T cell receptor repertoire and function in patients with DiGeorge syndrome and velocardiofacial syndrome

DiGeorge syndrome (DGS) and velocardiofacial syndrome (VCFS) are associated with chromosome 22q11.2 deletion. Limited information is available on the T cell receptor (TCR) Vbeta repertoire. We therefore investigated TCR Vbeta families in lymphocytes isolated from blood and thymic samples of seven patients with DGS and seven patients with VCFS, all with 22q11.2 deletion. We also studied activities related to TCR signalling including in vitro proliferation, anti-CD3-induced protein tyrosine phosphorylation, and susceptibility to apoptosis. Reduced CD3+ T cells were observed in most patients. Spontaneous improvement of T cell numbers was detected in patients, 3 years after the first study. Analysis of CD4+ and CD8+ TCR Vbeta repertoire in peripheral and thymic cells showed a normal distribution of populations even if occasional deletions were observed. Lymphoproliferative responses to mitogens were comparable to controls as well as anti-CD3-induced protein tyrosine phosphorylation. Increased anti-CD3-mediated apoptosis was observed in thymic cells. Our data support the idea that in patients surviving the correction of cardiac anomalies, the immune defect appears milder than originally thought, suggesting development of a normal repertoire of mature T cells.

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.

Longitudinal analysis of lymphocyte function and numbers in the first year of life in chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome)

Chromosome 22q11.2 deletion syndrome is a common syndrome typically consisting of variable cardiac defects, hypoparathyroidism, developmental delay, and immunodeficiency. The hemizygous deletion has variable effects on the immune system even within the same kindred, and the extent of the immunodeficiency is difficult to predict. Some patients have shown improvement over time; however, this is the first prospective longitudinal study of the dynamic nature of the immunodeficiency. Nineteen patients were studied prospectively between 1994 and 1997. The results of the newborn immunologic studies in the chromosome 22q11.2 deletion group were significantly different from those of a group of newborns with cardiac disease due to other causes. Peripheral blood T-cell numbers were decreased in the chromosome 22q11.2 deletion group, although T-cell function was largely preserved. The group as a whole demonstrated few changes in the first year of life, but a subset of patients with markedly diminished T-cell numbers did demonstrate improvement. Therefore, improvement in peripheral blood T-cell counts is variable in chromosome 22q11.2 deletion syndrome. The patients with the lowest T-cell counts improved the most in the first year of life.

Transplantation of thymus tissue in complete DiGeorge syndrome

BACKGROUND

The DiGeorge syndrome is a congenital disorder that affects the heart, parathyroid glands, and thymus. In complete DiGeorge syndrome, patients have severely reduced T-cell function.

METHODS

We treated five infants (age, one to four months) with complete DiGeorge syndrome by transplantation of cultured postnatal thymus tissue. Follow-up evaluations included immune phenotyping and proliferative studies of peripheral-blood mononuclear cells plus biopsy of the thymus allograft. Thymic production of new T cells was assessed in peripheral blood by tests for T-cell-receptor recombination excision circles, which are formed from excised DNA during the rearrangement of T-cell-receptor genes.

RESULTS

After the transplantation of thymus tissue, T-cell proliferative responses to mitogens developed in four of the five patients. Two of the patients survived with restoration of immune function; three patients died from infection or abnormalities unrelated to transplantation. Biopsies of grafted thymus in the surviving patients showed normal morphologic features and active T-cell production. In three patients, donor T cells could be detected about four weeks after transplantation, although there was no evidence of graft-versus-host disease on biopsy or at autopsy. In one patient, the T-cell development within the graft was demonstrated to accompany the appearance of recently developed T cells in the periphery and coincided with the onset of normal T-cell function. In one patient, there was evidence of thymus function and CD45RA+CD62L+ T cells more than five years after transplantation.

CONCLUSIONS

In some infants with profound immunodeficiency and complete DiGeorge syndrome, the transplantation of thymus tissue can restore normal immune function. Early thymus transplantation - before the development of infectious complications - may promote successful immune reconstitution.

Possible extrathymic development of nonfunctional T cells in a patient with complete DiGeorge syndrome

Complete DiGeorge syndrome is characterized by the clinical triad of cardiac malformation, hypocalcemia, and T cell immunodeficiency due to congenital athymia. We describe an infant with complete DiGeorge syndrome who at presentation had no circulating T cells detectable by flow cytometry. The patient spontaneously developed circulating T cells but these cells did not proliferate in response to mitogens. The T cell receptor Vbeta repertoire was severely restricted. All T cells were host, not maternal, as assessed by fluorescent in situ hybridization evaluation of 22q11 hemizygosity. At autopsy, this patient had no grossly detectable thymus tissue and no microscopic evidence for thymopoiesis. These findings suggest that appearance of T cells in infants with complete DiGeorge syndrome may represent oligoclonal expansions of a small number of T cells that may have matured extrathymically and which do not respond in vitro to mitogen stimulation.

Juvenile rheumatoid arthritis and del(22q11) syndrome: a non-random association

Del(22q11) is a common microdeletion syndrome with an extremely variable phenotype. Besides classical manifestations, such as velocardiofacial (Shprintzen) or DiGeorge syndromes, del(22q11) syndrome may be associated with unusual but probably causally related anomalies that expand its phenotype and complicate its recognition. We report here three children with the deletion and a chronic, erosive polyarthritis resembling idiopathic cases of juvenile rheumatoid arthritis (JRA). Patient 1, born in 1983, initially presented with developmental delay, facial dysmorphism, velopharyngeal insufficiency, and severe gastro-oesophageal reflux requiring G tube feeding. From the age of 3 years, he developed JRA, which resulted in severe restrictive joint disease, osteopenia, and platyspondyly. Patient 2, born in 1976, had tetralogy of Fallot and peripheral pulmonary artery stenosis. She developed slowly, had mild dysmorphic facial features, an abnormal voice, and borderline intelligence. JRA was diagnosed at the age of 5 years. The disorder followed a subacute course, with relatively mild inflammatory phenomena, but an extremely severe skeletal involvement with major osteopenia, restrictive joint disease (bilateral hip replacement), and almost complete osteolysis of the carpal and tarsal bones with phalangeal synostoses, leading to major motor impairment and confinement to a wheelchair. Patient 3, born in 1990, has VSD, right embryo-toxon, bifid uvula, and facial dysmorphism. She developed JRA at the age of 1 year. She is not mentally retarded but has major speech delay secondary to congenital deafness inherited from her mother. In the three patients, a del(22q11) was shown by FISH analysis. These observations, and five other recently published cases, indicate that a JRA-like syndrome is a component of the del(22q11) spectrum. The deletion may be overlooked in those children with severe, chronic inflammatory disorder.

Increased spontaneous apoptosis in T lymphocytes in DiGeorge anomaly

The aim of this study was to determine whether increased apoptosis in peripheral blood lymphocytes plays a role in T cell deficiency associated with DiGeorge anomaly. T cell subsets from a patient with DiGeorge anomaly were examined for the expression of Fas, FasL, Bcl-2 and Bcl-XL at the protein level with monoclonal antibodies, using dual-colour flow cytometry, and at the mRNA level in mononuclear cells by quantitative reverse transcriptase-polymerase chain reaction. In vitro spontaneous apoptosis was examined by propidium iodide staining and DNA fragmentation, using flow cytometry and gel electrophoresis, respectively. Fas and FasL expression, both at the level of protein and of mRNA, was increased, whereas Bcl-2 expression was decreased both at the level of protein and of mRNA. However, no difference in Bcl-XL expression was observed between the patient and an age-matched control. A significant proportion of both CD4+ and CD8+ T cells from the patients underwent spontaneous apoptosis, whereas almost no spontaneous apoptosis was observed in the age-matched control. These data suggest that spontaneous apoptosis in T lymphocytes, at least in part, may be responsible for T cell deficiency in DiGeorge anomaly.

Lack of correlation between impaired T cell production, immunodeficiency, and other phenotypic features in chromosome 22q11.2 deletion syndromes

Monosomic deletions of chromosome 22q11.2 are the leading cause of DiGeorge syndrome, velocardiofacial syndrome, and conotruncal anomaly face syndrome. DiGeorge syndrome was originally described as an immunodeficiency disorder secondary to impaired T cell production due to thymic aplasia or hypoplasia; however, the frequency of immunodeficiency in the other clinical syndromes associated with the chromosome 22q11.2 microdeletion has not been previously investigated. This study examines the frequency and severity of impaired T cell production and immunodeficiency in chromosome 22q11.2 deletion syndromes and the relationship of the immunodeficiency to specific phenotypic features. Sixty patients over 6 months of age with the characteristic chromosome 22q11.2 deletion underwent immunologic evaluations. Seventy-seven percent of patients with chromosome 22q11.2 deletions were found to have evidence of immunocompromise. The severity of the immunodeficiency did not correlate with any particular phenotypic feature, nor was it restricted to patients who were categorized as having DiGeorge syndrome. Therefore, impaired T cell production and impaired immunologic function are common in patients with deletions of chromosome 22q11.2. The presence or severity of the immunocompromise cannot be predicted based on other phenotypic features and each child should be individually assessed for immune function.

Complete DiGeorge syndrome: persistence of profound immunodeficiency

OBJECTIVE

DiGeorge syndrome is characterized by developmental defects of the heart, parathyroid glands, and thymus. The objective of this study was to determine whether T-cell function spontaneously improves in patients with DiGeorge syndrome who have profoundly depressed T-cell proliferative responses to mitogens at presentation, regardless of the T-cell count.

STUDY DESIGN

We conducted a retrospective chart review of eight patients with DiGeorge syndrome who had no proliferative responses to mitogens on presentation.

RESULTS

Despite lack of responsiveness of the patients' peripheral blood lymphocytes to mitogens, T cells were occasionally detected, and the patients' cells often responded to IL-2 and in mixed lymphocyte reactions. Unresponsiveness to mitogens and clinical immunodeficiency persisted without immune-based therapy. One patient is alive and well after immunoreconstitution from thymic transplantation. The others either died early of complications of their disease such as gastroesophageal reflux with aspiration (2 patients) or infection (2 patients) or died after attempts at immunorestorative therapy with IL-2, thymus transplantation, or bone marrow transplantation (3 patients).

CONCLUSION

Eight patients with DiGeorge syndrome who were first seen with no mitogen responsiveness did not improve spontaneously. We recommend HLA-identical bone marrow transplantation or thymic transplantation for these patients as soon as the diagnosis is confirmed.

Juvenile rheumatoid arthritis-like polyarthritis in chromosome 22q11.2 deletion syndrome (DiGeorge anomalad/velocardiofacial syndrome/conotruncal anomaly face syndrome)

OBJECTIVE

To investigate the association of polyarthritis and chromosome 22q11.2 deletions.

METHODS

Eighty patients with chromosome 22q11.2 deletion syndrome followed up at The Children's Hospital of Philadelphia were examined for evidence of arthropathy or arthritis. Patients with chromosome 22q11.2 deletion syndrome and polyarthritis underwent laboratory evaluations of immunologic function to determine the relationship of their immunodeficiency to the polyarthritis.

RESULTS

The prevalence of polyarthritis in patients with chromosome 22q11.2 deletion syndrome was markedly increased over the prevalence of polyarticular juvenile rheumatoid arthritis (JRA) in the general population. All 3 patients with polyarthritis had evidence of impaired T cell function. Two of the patients with polyarthritis also had IgA deficiency.

CONCLUSION

The chromosome 22q11.2 deletion syndrome represents a primary T cell disorder which can be associated with a JRA-like polyarthritis. All 3 patients with polyarthritis had evidence of more extensive immunoregulatory derangements than those typically seen in patients with chromosome 22q11.2 deletion, and these derangements may have predisposed to the development of polyarthritis.

Juvenile rheumatoid arthritis in velo-cardio-facial syndrome: coincidence or unusual complication?

We report on two patients with velo-cardio-facial syndrome (VCFS) and juvenile rheumatoid arthritis (JRA). The first, a 9-year-old girl, presented with microcephaly, characteristic face, congenital heart disease, and velopharyngeal insufficiency. Fluorescence in situ hybridization (FISH) study showed deletion of D22S75 (N25), confirming the diagnosis of VCFS. At age 7, she developed joint pain, and polyarticular JRA was diagnosed. Awareness of this case led to the subsequent diagnosis of VCFS (also confirmed by FISH) in another, unrelated 12-year-old girl with characteristic face, hypernasal speech, and obesity. JRA was first diagnosed in this case at age 5 years, and she subsequently developed severe polyarticular disease. Neither patient had clinical or laboratory evidence of immunodeficiency. This observation represents the first report of the association of JRA with VCFS and raises the question of whether this is a coincidental association or a rare complication of this condition.

Latent hypoparathyroidism in children with conotruncal cardiac defects

BACKGROUND

DiGeorge anomaly is characterized by hypoplasia or atresia of the thymus and parathyroid glands resulting in T cell-mediated deficiency, hypocalcemic hypoparathyroidism, and conotruncal cardiac defects. It usually is associated with deletions of chromosomal region 22q11. We hypothesized that the stimulated (secretory reserve) but not the constitutive secretion of parathyroid hormone would be reduced in normocalcemic children with conotruncal cardiac defects but no overt immune deficiency and would be related to the presence of a deletion in the DiGeorge chromosomal region of 22q11.

METHODS AND RESULTS

Blood-ionized calcium and serum-intact parathyroid hormone were measured at baseline and seven more times during hypocalcemia induced during cardiopulmonary bypass in 22 patients and 10 control subjects with an atrial septal defect. Chromosomal deletions were detected by fluorescent in situ hybridization and DNA dosage analysis. There were no differences in basal calcium and parathyroid hormone levels between patients and control subjects. All had increased parathyroid hormone in response to hypocalcemia; despite lower calcium levels, parathyroid hormone levels were lower in patients. The parathyroid hormone secretory reserve in 14 of 22 patients was reduced compared with control subjects; 4 of the 14 had deletions.

CONCLUSIONS

A significant number of children with conotruncal cardiac defects have normocalcemia and a normal constitutive level of parathyroid hormone but deficient parathyroid hormone secretory reserve; about 30% also have 22q11 deletions. Such children may be at risk for the later development of hypocalcemic hypoparathyroidism.

Autosomal dominant "Opitz" GBBB syndrome due to a 22q11.2 deletion

We report on a family with autosomal dominant paternally inherited "Opitz" GBBB syndrome and an additional case with findings which have been reported in that syndrome. In each case the propositus presented with a vascular ring. Since a vascular ring may be a sign of a 22q11.2 deletion [Zacki et al., 1995], FISH (fluorescence in situ hybridization) studies were performed. These studies demonstrated a 22q11.2 deletion in the 3 affected individuals. Review of Opitz GBBB syndrome and the 22q11.2 microdeletion syndrome demonstrates significant overlap of manifestations including both facial characteristics and structural anomalies. Based on the phenotypic overlap and the presence of a 22q11.2 deletion in our patients with Opitz GBBB syndrome and the presence of a deletion in a patient with lung hypoplasia, absent pulmonary artery, and long segment tracheomalacia, we propose that, in some cases, the Opitz GBBB syndrome may be due to a 22q11.2 deletion. This enlarges the list of "syndromes" associated with the 22q11.2 deletion, which presently includes most patients with DiGeorge, velocardiofacial, and conotruncal anomaly face syndrome.

Clinical and molecular study of DiGeorge sequence

DiGeorge sequence (DGS) is a developmental field defect of the third and fourth pharyngeal pouches. The cardinal features of the syndrome are hypo- or aplasia of the thymus and parathyroids, congenital heart defect of the conotruncal type and characteristic facial dysmorphism. Such a pattern of malformations has been associated with various conditions but it is now well established that most cases of DGS are due to haplo-insufficiency of the chromosome 22q11 region. We report here a series of 16 patients, including a familial case. Minimal criteria for inclusion in this series were two or more of the following features: conotruncal heart defect, hypocalcaemia, hypoplastic/absent thymus and typical facial dysmorphism. Molecular analysis with specific probes of the 22q11 region was conducted in all patients according to two methods, fluorescent in situ hybridization and DNA dosage analysis. A deletion was found at the molecular level in all patients. We emphasize the fact that clinical analysis remains an important step of the diagnosis. The implication of these molecular techniques on diagnosis, prognosis and genetic counselling of DGS are discussed.