Endocrine aspects of the 22q11.2 deletion syndrome

Thyroid function and morphology in subjects with microdeletion of chromosome 22q11 (del(22)(q11))

INTRODUCTION

Monoallelic microdeletion of chromosome 22q11 (22q11DS) is considered to be the commonest human microdeletion syndrome. Abnormalities of thyroid function are sporadically reported in this syndrome, but very few studies have specifically assessed this issue, and thyroid morphology has not been systematically studied.

DESIGN

To evaluate the prevalence of abnormalities of thyroid function and morphology in a cohort of paediatric and adult patients with 22q11DS.

METHODS

Thirty patients with 22q11DS (median age 9.7, range 1.5-43.9 years) were studied. In all subjects, serum free-T(3), free-T(4), TSH, thyroperoxidase, thyroglobulin, and TSHr auto-antibodies, as well as thyroid ultrasonographic data, were evaluated and compared with age- and sex-matched healthy control groups, for paediatric and adult patients.

RESULTS

Fourteen (46.6%) patients showed thyroid hypoplasia involving the entire gland. In all the patients, the volume of the left lobe of the thyroid was significantly reduced (P < 0.01). Among the subjects with thyroid hypoplasia, 10 out of 14 (71%) showed a concomitant heart malformation, a condition that was present in five (31%) of the subjects with a normal thyroid volume (P < 0.05). Seven (23.3%) cases of subclinical hypothyroidism and one (3.3%) case of overt hypothyroidism were identified. Three (10%) patients were positive for thyroid auto-antibodies. Of the patients with overt and subclinical hypothyroidism, five out of eight (62.5%) patients showed thyroid hypoplasia.

CONCLUSIONS

This study confirms the presence of alterations of thyroid function in 22q11DS, and also suggests a frequent occurrence of abnormalities in thyroid morphology in these subjects. Patients with 22q11DS should be monitored for thyroid function, and thyroid ultrasound screening should be considered, especially in those patients with changes in thyroid function or congenital heart malformations. The possible relationship between developmental abnormalities in the heart and the thyroid gland should be confirmed.

Seizures and EEG findings in an adult patient with DiGeorge syndrome: a case report and review of the literature

This is the first case report to describe the EEG findings in a patient with DiGeorge syndrome who survived into adulthood. The patient developed generalized tonic-clonic seizures when she was 9 years old and these were associated with hypocalcemia. Despite treatment with calcium, seizures persisted and the patient required antiepileptic medications. She was eventually controlled with oxcarbazepine. An MRI of the head was normal. An EEG showed independent spike and wave discharges emanating from the left temporal and right frontal region. The presence of focal findings on EEG, the lack of complete response to calcium therapy, and the need for antiepileptic drug therapy indicate that some of these patients may be inherently predisposed to developing epilepsy.

Parathyroid hormone reserve in 22q11.2 deletion syndrome

OBJECTIVE

We hypothesized that most patients with 22q11.2 deletion and a history of hypocalcemia have inadequate parathyroid function, manifested by intact parathyroid hormone levels below normal. We aimed to evaluate intact parathyroid hormone levels both during normocalcemia and at hypocalcemia, in this population.

STUDY DESIGN

Retrospective chart review of 103 patients with 22q11.2 deletion born since 1997 and cared for at the Children's Hospital of Philadelphia. Calcium and intact parathyroid hormone drawn simultaneously were recorded, along with clinical presentation at hypocalcemia.

RESULTS

Forty-seven simultaneous Ca/intact parathyroid hormone values were available. Seventy-nine percent of calcium levels and 81% of parathyroid hormone levels were within normal range. There were 19 patients with a history of symptomatic hypocalcemia, for whom any available simultaneous Ca/parathyroid hormone levels, before, during, or after hypocalcemia were analyzed. In this subgroup, 59% of calcium and 76% of parathyroid hormone levels were normal. None had an intact parathyroid hormone of >39.2 pg/mL at hypocalcemia. Seventy-three percent of hypocalcemic events had a precipitating stressor.

CONCLUSIONS

Hypoparathyroidism in 22q11.2 deletion is mild, manifesting as a phenomenon of decreased parathyroid hormone reserve. Subjects are normocalcemic most of the time, but are unable to mount elevated intact parathyroid hormone levels, and therefore unable to correct hypocalcemia, in response to stressors.

Seizures as the first manifestation of chromosome 22q11.2 deletion syndrome in a 40-year old man: a case report

BACKGROUND

The microdeletion of chromosome 22q11.2 is the most common human deletion syndrome. It typically presents early in life and is rarely considered in adult patients. As part of the manifestations of this condition, patients can have parathyroid glandular involvement ranging from hypocalcemic hypoparathyroidism to normocalcemia with normal parathryroid hormone levels. The first manifestation of the syndrome might be seizures due to profound hypocalcemia.

CASE PRESENTATION

A 40-year-old man without significant past medical history presented with a new-onset generalized tonic-clonic seizure. He had no personal history of hypocalcemia or seizures. Physical examination was remarkable for short stature, hypertelorism, prominent forehead and nasal voice. His initial laboratory examination showed hypocalcemia (Calcium 5.2 mg/dl and Calcium ionized 0.69 mmol/l) with hypoparathyroidism (Parathyroid hormone intact < 2.5 pg/ml. NV: 14-72 pg/ml). Urine Calcium was 3 mg/dl on a spot and 88 mg in a 24-hour urine collection (NV: 100-300 mg/24 hs). The electrocardiogram showed a prolonged corrected QT interval. Echocardiogram, abdominal ultrasound and electroencephalogram were normal. A computer tomography of the brain showed basal ganglia calcification. The subtle physical findings and the presence of idiopathic hypoparathyroidism motivated the performance of fluorescent in situ hybridization which demonstrated a microdeletion on one of the homologs 22q11.2. The patient was treated with calcium citrate and calcitriol with good response.

CONCLUSION

Microdeletion of chromosome 22q11.2 is among the most clinically variable syndromes, with more than 180 features associated with the deletion. It has a variable phenotypical expression, requiring a high level of awareness for its early diagnosis. Seizures, related to marked hypocalcemia due to idiopathic hypoparathyroidism, might be the presenting feature in an adult patient with this syndrome.

Parathyroid gland dysfunction in 22q11.2 deletion syndrome

BACKGROUND

22q11 deletion syndrome (22q11DS) is characterized by conotruncal cardiac defects and hypoplasia of parathyroid glands and thymus, which result in variable hypoparathyroidism (HPT) and immune deficiency.

METHODS

To study the course of HPT and the spectrum of other associated manifestations we evaluated all patients with 22q11DS, confirmed by fluorescence in situ hybridization, and HPT who were under follow-up at the Calcium-bone clinic, The Hospital for Sick Children, Toronto. Patients were clinically assessed and their hospital records were reviewed.

RESULTS

Eighteen patients were included. At follow-up assessment at median age of 7.3 years HPT was judged complete in 11 (61%) and partial in 7 patients (39%). Patients with complete HPT presented with hypocalcemia later (median age at diagnosis 2.4 vs. 0.0 years) and more often with a hypocalcemic seizure than patients with partial HPT (73 vs. 29%). The spectrum of other associated manifestations did not differ between the groups.

CONCLUSIONS

HPT in patients with 22q11DS is often partial. Many of the patients present with a hypocalcemic seizure which is predictive of complete HPT. Patients with complete and partial HPT do not differ in respect to their other associated features. Patients with features of 22q11DS should be actively screened for hypocalcemia to prevent development of symptomatic hypocalcemia.

Cellular and genetic basis of primary immune deficiencies

Knowledge of the genetic mutations of primary immune deficiency syndromes has grown significantly over the last 30 years. In this article the authors present an overview of the clinical aspects, laboratory evaluation, and genetic defects of primary immunodeficiencies, with an emphasis on the pathophysiology of the known molecular defects. This article is designed to give the primary pediatrician a general knowledge of this rapidly expanding field.

antiphospholipid antibodies syndrome associated with hyperhomocysteinemia related to MTHFR Gene C677T and A1298C heterozygous mutations in a young man with idiopathic hypoparathyroidism (DiGeorge syndrome)

CONTEXT

Antiphospholipid syndrome (APS, or Hughes' syndrome) is a systemic autoimmune disorder characterized by antiphospholipid antibody positivity, which may lead to arterial and/or venous thrombosis. Hyperhomocysteinemia (HHcy), variously associated with 5,10-methylene tetrahydrofolate reductase (MTHFR) gene point mutations, is also implicated in thromboembolic events. The association of APS and HHcy has already been described but has never been reported in patients with DiGeorge syndrome (DGS), the most common contiguous-gene deletion syndrome (22q11.2) in humans, whose phenotype conversely includes bleeding disorders.

DATA ACQUISITION

In this report, we present the case of a 19-yr-old patient with a past medical history of learning disability and obesity affected with idiopathic hypoparathyroidism, metabolic syndrome, and diffuse vasculitis disorders. He was referred to our endocrinology clinic for the management of severe hypocalcemia. At the time of presentation he had been taking antiepileptic drugs for 2 wk and displayed facial dysmorphism (short neck, micrognathia, a small mouth, hypoplastic nasal alae, eye hypertelorism, and low-set simple ears). DGS was suspected and confirmed by both fluorescence in situ hybridization analysis and single nucleotide polymorphism-array analysis, which revealed contiguous gene microdeletion of the chromosome 22q11.2 in the minimal DiGeorge critical region, specifically at the gene locus D22S75 (N25).

CONCLUSIONS

APS, revealed by anti-beta-2-glycoprotein and anti-prothrombin antibodies positivity, and moderate HHcy related to heterozygous C677T and A1298C point mutations of the MTHFR gene were identified as a possible cause of thrombotic disorder responsible for the widespread presence of cutaneous and cerebral lesions.

Clinical features of 78 adults with 22q11 Deletion Syndrome

22q11 Deletion Syndrome (22q11DS) is a common microdeletion syndrome with multisystem expression. Phenotypic features vary with age, ascertainment, and assessment. We systematically assessed 78 adults (36 M, 42 F; mean age 31.5, SD 10.5 years) with a 22q11.2 deletion ascertained through an adult congenital cardiac clinic (n = 35), psychiatric-related sources (n = 39), or as affected parents of subjects (n = 4). We recorded the lifetime prevalence of features requiring attention, with 95% confidence intervals (CI) not overlapping zero. Subtle learning difficulties, hypernasality and facial gestalt were not included. We investigated ascertainment effects using non-overlapping subgroups ascertained with tetralogy of Fallot (n = 31) or schizophrenia (n = 31). Forty-three features met inclusion criteria and were present in 5% or more patients, including several of later onset (e.g., hypothyroidism, cholelithiasis). Number of features per patient (median 9, range 3-22) correlated with hospitalizations (P = 0.0002) and, when congenital features were excluded, with age (P = 0.02). Adjusting for ascertainment, 25.8% (95% CI, 9.5-42.1%) of patients had cardiac anomalies and 22.6% (95% CI, 7.0-38.2%) had schizophrenia. Ascertainment subgroups were otherwise similar in median number and prevalence of features. Non-characteristic features are common in 22q11DS. Adjusting for ascertainment effects is important. Many treatable conditions may be anticipated and features may accumulate over time. The results have implications for clinical assessment and management, genetic counseling and research into pathophysiological mechanisms.

Velo-cardio-facial syndrome: the pediatric otolaryngologist's perspective

PURPOSE OF REVIEW

The understanding of velo-cardio-facial syndrome has grown markedly since the initial descriptions of this common genetic disorder nearly 30 years ago. Our knowledge of the syndrome has advanced in part from opportunities to monitor many patients into adulthood because of advances in the fields of cardiothoracic surgery and immunology. Longitudinal study has brought to light psychiatric and behavioral features of the syndrome that are often not apparent until late adolescence or the early adult years. Certain endocrine and immunologic features of the syndrome thought to be resolved in childhood are now witnessed in older patients. Variable expression and lack of disease awareness are two major factors that contribute to the delays in diagnosis in many cases. To address this, there has been a call to delineate screening parameters for patients at risk of carrying the deletion.

RECENT FINDINGS

Several areas are highlighted in this review, reflecting the focus of scholarly work on velo-cardio-facial syndrome in the past year. Molecular genetics has shown smaller deletions in many families with the syndrome. The gene TBX1 has been found to be important to the phenotype. Surgical outcomes data reveal the greater challenges involved in correcting velopharyngeal insufficiency.

SUMMARY

Defining the genetic basis of velo-cardio-facial syndrome will allow clinicians and basic scientists to make further inroads into understanding the variable expressivity of this syndrome. It is also important to be aware of the continued diagnostic challenges encountered by clinicians in attempts to improve the detection of patients with this syndrome.

Morphological appearance and chemical composition of enamel in primary teeth from patients with 22q11 deletion syndrome

Patients with 22q11 deletion syndrome have many and complex medical problems, including hypocalcemia and/or hypoparathyroidism. Odontological findings include enamel aberrations in both dentitions. In order to describe enamel morphology, chemical composition in primary teeth, and to investigate the relationship between medical history and morphological appearance, dental enamel was investigated in 38 exfoliated primary teeth from 15 children and adolescents. Morphology was studied by the use of a polarized light microscope, microradiography, scanning electron microscopy, X-ray microanalysis, and secondary ion mass spectrometry. The morphological findings were compared with medical history. The teeth showed, in principle, a normal morphological appearance with regard to prism structure. A high frequency of aberrations, such as hypomineralization, hypoplasia and extra incremental lines, were found. The majority of the aberrations were found around the neonatal line. There was a relationship between high numbers of medical problems in the patients and enamel deviations. The result supports the hypothesis of under-reporting of both hypocalcemia and hypoparathyroidism in patients with 22q11 deletion syndrome.

Endocrine manifestations of chromosome 22q11.2 microdeletion syndrome

BACKGROUND

Endocrine abnormalities, including hypocalcemia, thyroid dysfunction, and short stature, are associated with chromosome 22q11.2 microdeletion syndrome. This study was undertaken to examine the frequencies and clinical features of endocrine abnormalities in patients with 22q11.2 microdeletion syndrome.

METHODS

We analyzed 61 patients with 22q11.2 microdeletion syndrome diagnosed based on the verification of microdeletion by fluorescent in situ hybridization (FISH) using a probe of the DiGeorge syndrome critical region (TUPLE1) at 22q11.2 and a control probe, ARSA at 22q13. Serum total calcium, phosphorus, and intact parathyroid hormone (PTH) levels were measured, thyroid function test was performed, and serum IGF-1 and IGFBP-3 levels were also estimated. Height and weight of patients were compared with individual chronological ages.

RESULTS

Hypocalcemia was found in 20 patients (32.8%), and overt hypoparathyroidism in 8 (13.1%). Two patients (3.3%) showed autoimmune thyroid diseases, 1 each with Graves' disease and Hashimoto thyroiditis. Ten patients (16.4%) were below the third percentile in height, but the serum IGF-1 level was normal in 9 out of these 10 patients.

CONCLUSION

Our findings show that patients with chromosome 22q11.2 microdeletion syndrome present with variable endocrine manifestations and variable clinical phenotypes. In addition to FISH analysis, careful endocrine evaluations are required in patients with this microdeletion syndrome, particularly for those with hypoparathyroidism or thyroid dysfunction.

Syndrome de délétion 22q11 et maladie de Basedow. À propos de trois observations pédiatriques

Hypothyroidism is a well recognized complication of 22q11.2 deletion syndrome. Auto-immune hyperthyroidism is less common. We report three patients with a 22q11.2 deletion and Graves' disease diagnosed at age 17, 14 and 11 years, respectively. The clinical and biological presentation was typical for auto-immune hyperthyroidism. Graves' disease should be periodically sought during the follow-up program of patients with 22q11.2 deletion syndrome.

A case of chromosome 22q11 deletion syndrome diagnosed in a 32-year-old man with hypoparathyroidism

Congenital hypoparathyroidism typically manifests with hypocalcemia with or without associated characteristic physical findings and is usually diagnosed during the neonatal period. This report describes an African-American male who was diagnosed at age 32 yr to have dysgenesis of the parathyroid glands due to chromosome 22 microdeletion. Symptomatic hypocalcemia did not develop until age 14 yr, a few weeks after initiation of anticonvulsant therapy for generalized tonic-clonic seizures. Because of the timing for onset of symptomatic hypocalcemia, it was presumed that the patient had anticonvulsant-induced hypocalcemia, and he carried that diagnosis for 18 yr. Chromosome 22q11 deletion syndrome was first suspected at age 32 yr, based on the findings of subtle dysmorphic facial features and a history of learning disability in a patient with PTH-deficient hypocalcemia. The diagnosis was confirmed by fluorescence in situ hybridization analysis. This case underscores the variable clinical presentation of this congenital form of hypoparathyroidism. Chromosome 22q11 microdeletions are relatively common, and the diagnosis should be considered even in adults with hypoparathyroidism because of the potential benefit of genetic counseling.

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

A population-based study of the 22q11.2 deletion: phenotype, incidence, and contribution to major birth defects in the population

OBJECTIVES

Although several studies describe the 22q11.2 deletion, population-based data are scant. Such data are needed to evaluate properly the impact, distribution, and clinical presentation of the deletion in the population. Our goals were to assess the population-based birth prevalence of the 22q11.2 deletion and its associated phenotype and its impact on the occurrence of heart defects.

METHODS

We evaluated data on infants who were born from 1994 through 1999 to women who resided in metropolitan Atlanta. We matched records from the Metropolitan Atlanta Congenital Defects Program (a population-based registry with active case ascertainment), the Sibley Heart Center at Children's Healthcare of Atlanta, and the Division of Medical Genetics at Emory University. We used birth certificate data for the denominators of the rates.

RESULTS

We identified 43 children with laboratory-confirmed 22q11.2 deletion among 255 849 births. The overall prevalence was 1 in 5950 births (95% confidence interval: 1 in 4417 to 1 in 8224 births). The prevalence was between 1 in 6000 and 1 in 6500 among whites, blacks, and Asians and 1 in 3800 among Hispanics. Most affected children (81%) had a heart defect, and many (1 in 3) had major extracardiac defects (other than velopalatal anomalies), including anomalies of the central nervous system. Overall, the deletion contributed to at least 1 of every 68 cases of major heart defects identified in the total birth cohort and, in particular, to 1 of every 2 cases diagnosed with interrupted aortic arch type B, 1 of every 5 with truncus arteriosus, and 1 of every 8 with tetralogy of Fallot.

CONCLUSIONS

The 22q11.2 deletion was common in this birth population. The clinical phenotype included a wide and variable spectrum of major cardiac and extracardiac anomalies. From these population-based data, one can estimate that at least 700 affected infants are born annually in the United States. Population-based estimates such as these should be useful to medical professionals and policy makers in planning for the optimal care of people with the 22q11.2 deletion.

Parathyroid function and growth in 22q11.2 deletion syndrome

OBJECTIVE

To determine the frequency and expression of hypoparathyroidism and the factors of short stature in 22q11.2 deletion syndrome to optimize clinical care.

STUDY DESIGN

Cross-sectional study of 39 patients 9.7 +/- 0.8 (2.5-20) years of age.

RESULTS

The congenital abnormalities were cardiac defects in 33 of 39, thymus hypoplasia in 15 of 18 evaluated, and craniofacial dysmorphy in all; 15 patients (39%) had had one or more seizures. Before evaluation, 12 patients were hypocalcemic, with (n = 4) or without clinical manifestations, diagnosed before 1 month in 10 cases, at 3 months or 12 years in two others. At evaluation, 9 patients were hypocalcemic, 5 of 9 had been hypocalcemic, and 8 others had parathyroid hormone (PTH) concentrations low for their ionized calcium. One had high PTH without hypocalcemia and 2 were hypercalcemic. The values were below -2 SD at birth for weight and/or height in 26% of cases and at evaluation for height and body mass index in 23% and for insulin-like growth factor-I in 37%.

CONCLUSIONS

Parathyroid function was abnormal in 27 of 39 (69%) patients. This was not diagnosed in the majority. Short stature was probably due to intrauterine growth restriction, underweight, and growth hormone deficiency, as suggested by low insulin-like growth factor I.

Parathyroid hormone is essential for normal fetal bone formation

Parathyroid hormone (PTH) is a potent pharmacologic inducer of new bone formation, but no physiologic anabolic effect of PTH on adult bone has been described. We investigated the role of PTH in fetal skeletal development by comparing newborn mice lacking either PTH, PTH-related peptide (PTHrP), or both peptides. PTH-deficient mice were dysmorphic but viable, whereas mice lacking PTHrP died at birth with dyschondroplasia. PTH-deficient mice uniquely demonstrated diminished cartilage matrix mineralization, decreased neovascularization with reduced expression of angiopoietin-1, and reduced metaphyseal osteoblasts and trabecular bone. Compound mutants displayed the combined cartilaginous and osseous defects of both single mutants. These results indicate that coordinated action of both PTH and PTHrP are required to achieve normal fetal skeletal morphogenesis, and they demonstrate an essential function for PTH at the cartilage-bone interface. The effect of PTH on fetal osteoblasts may be relevant to its postnatal anabolic effects on trabecular bone.