Impaired Immune Function in Patients With Chronic Postsurgical Hypoparathyroidism: Results of the EMPATHY Study.

CONTEXT: Despite the pivotal role of calcium signaling in immune response, little is known about immune function in patients affected by hypoparathyroidism. OBJECTIVE: This work aimed to evaluate immune function in hypoparathyroidism. METHODS: The Evaluation of iMmune function in Postsurgical and AuToimmune HYpoparathyroidism (NCT04059380) is a case-control, cross-sectional study set in an Italian referral center. Participants included 20 patients with postsurgical hypoparathyroidism (12 females) and 20 age- and sex-matched controls. Main outcome measures included calcium metabolism assessment, peripheral blood mononuclear cells (PBMC) profiling via flow cytometry, parathyroid hormone receptor 1 (PTHr1) expression analysis using immunofluorescence and PrimeFlow RNA assay, gene expression analysis via real-time polymerase chain reaction, cytokine measurement, and evaluation of infectious disease frequency and severity. RESULTS: Immune cell profiling revealed decreased monocytes, regulatory, naive, and total CD4+ T lymphocytes, which correlated with total calcium, ionized calcium, and PTH levels, in patients with hypoparathyroidism. Patients with hypoparathyroidism had a higher CD3-CD56+ natural killer (NK) cell count, which inversely correlated with calcium, PTH, and vitamin D levels. Furthermore, they exhibited decreased tumor necrosis factor (TNF) and granulocyte-macrophage colony-stimulating factor gene expression and decreased circulating TNF levels. Gene expression and immunofluorescence analysis confirmed PTHr1 expression in all PBMC lineages; however, the percentage of cells expressing PTHr1 was lower, whereas the intensity of PTHr1 expression in monocytes, total T lymphocytes, CD8+CD4+ and CD4+ T lymphocytes, and total NK cells was higher in patients with hypoparathyroidism. CONCLUSIONS: This study describes for the first time the immune alterations in patients with hypoparathyroidism receiving conventional therapies, supporting the immunoregulatory role of PTH and proposing an explanation for the increased susceptibility to infections observed in epidemiological studies.

Calcium-sensing receptor autoantibody-mediated hypoparathyroidism associated with immune checkpoint inhibitor therapy: diagnosis and long-term follow-up.

BACKGROUND: Immune checkpoint inhibitors (ICIs) have produced significant survival benefit across many tumor types. However, immune-related adverse events are common including autoimmune responses against different endocrine organs. Here, a case of ICI-mediated hypoparathyroidism focusing on long-term follow-up and insights into its etiology is presented. CASE AND METHODS: A 73-year-old man developed severe symptomatic hypocalcemia after the initiation of ipilimumab and nivolumab for the treatment of metastatic melanoma. Hypoparathyroidism was diagnosed with undetectable intact parathyroid hormone (PTH). Immunoprecipitation assays, ELISAs, and cell-based functional assays were used to test the patient for antibodies against the calcium-sensing receptor (CaSR). NACHT leucine-rich repeat protein 5 (NALP5) and cytokine antibodies were measured in radioligand binding assays and ELISAs, respectively. RESULTS: The patient's symptoms improved with aggressive calcium and vitamin D supplementation. At 3 years and 3 months since the diagnosis of hypoparathyroidism, PTH was still inappropriately low at 7.6 pg/mL, and attempted discontinuation of calcium and calcitriol resulted in recurrent symptomatic hypocalcemia. Analysis for an autoimmune etiology of the patient's hypoparathyroidism indicated that CaSR antibodies were negative before treatment and detected at multiple time points afterwards, and corresponded to the patient's clinical course of hypoparathyroidism. CaSR antibodies purified from the patient's serum activated the human CaSR. The patient was seronegative for NALP5 and cytokine antibodies, indicating that their hypoparathyroidism was not a manifestation of autoimmune polyendocrine syndrome type 1. CONCLUSION: The etiology of hypocalcemia is likely autoimmune hypoparathyroidism caused by the development of CaSR-activating antibodies that might prevent PTH release from the parathyroid.

Activating Antibodies to The Calcium-sensing Receptor in Immunotherapy-induced Hypoparathyroidism.

CONTEXT: Immune checkpoint inhibitors (ICIs), such as programmed cell death protein-1 (PD-1), programmed cell death protein-ligand 1 (PD-L1), and cytotoxic T lymphocyte antigen-4 (CTLA-4) monoclonal antibodies, are approved for the treatment of some types of advanced cancer. Their main treatment-related side-effects are immune-related adverse events (irAEs), especially thyroid dysfunction and hypophysitis. Hypoparathyroidism, on the contrary, is an extremely rare irAE. OBJECTIVES: The aim of the study was to investigate the etiology of autoimmune hypoparathyroidism in a lung cancer patient treated with pembrolizumab, an anti-PD-1. METHODS: Calcium-sensing receptor (CaSR) autoantibodies, their functional activity, immunoglobulin (Ig) subclasses and epitopes involved in the pathogenesis of autoimmune hypoparathyroidism were tested. RESULTS: The patient developed hypocalcemia after 15 cycles of pembrolizumab. Calcium levels normalized with oral calcium carbonate and calcitriol and no remission of hypocalcemia was demonstrated during a 9-month follow-up. The patient was found to be positive for CaSR-stimulating antibodies, of IgG1 and IgG3 subclasses, that were able to recognize functional epitopes on the receptor, thus causing hypocalcemia. CONCLUSION: The finding confirms that ICI therapy can trigger, among other endocrinopathies, hypoparathyroidism, which can be caused by pathogenic autoantibodies.

Immune Checkpoint Inhibitor-Induced Hypoparathyroidism Associated With Calcium-Sensing Receptor-Activating Autoantibodies.

Context: Whereas therapy with immune checkpoint inhibitors (ICIs), such as nivolumab, have substantially improved survival in several types of cancer, increased attention has been given to adverse immune events associated with their use, including the development of endocrine autoimmunity. Objectives: First, to describe a patient with a 2-year history of metastatic small cell lung cancer who had been treated with nivolumab a few months before presentation with the signs and symptoms of severe hypocalcemia and hypoparathyroidism. Second, to investigate the etiology of the patient's hypoparathyroidism, including the presence of activating autoantibodies against the calcium-sensing receptor (CaSR), as humoral and cellular immune responses against the CaSR have been reported in patients with autoimmune hypoparathyroidism. Participants: A 61-year-old female was admitted with persistent nausea, vomiting, epigastric pain, constipation, and generalized weakness. Laboratory analyses showed low total serum calcium, ionized calcium, and parathyroid hormone (PTH). The patient was diagnosed with severe hypocalcemia as a result of autoimmune hypoparathyroidism after testing positive for CaSR-activating autoantibodies. Interventions: She was treated with intravenous calcium gluconate infusions, followed by a transition to oral calcium carbonate, plus calcitriol, which normalized her serum calcium. Results: Her serum PTH remained low during her hospitalization and initial outpatient follow-up, despite adequate repletion of magnesium. Conclusions: This case illustrates autoimmune hypoparathyroidism induced by ICI blockade. As ICIs are now used to treat many cancers, clinicians should be aware of the potential risk for hypocalcemia that may be associated with their use.

Presumptive Glucocorticoid-Induced Refractory Hypocalcemia in a Dog with Idiopathic Immune-Mediated Hypoparathyroidism, Thrombocytopenia, and Hemolytic Anemia.

Clinically relevant hypocalcemia is a well-documented complication of glucocorticoid administration in people with hypoparathyroidism. The current report describes the phenomenon in a dog. A 7 yr old neutered male Pomeranian was diagnosed with immune-mediated thrombocytopenia, immune-mediated hemolytic anemia, and primary hypoparathyroidism. This dog required long-term parenteral calcium gluconate to prevent clinical hypocalcemia despite appropriate doses of oral calcitriol and calcium carbonate. This is the first description of clinically significant presumptive glucocorticoid induced hypocalcemia in a dog with primary hypoparathyroidism.

Immunosuppressive therapy of autoimmune hypoparathyroidism in a patient with activating autoantibodies against the calcium-sensing receptor.

CONTEXT: Activating antibodies directed at the extracellular calcium-sensing receptor (CaSR) have been described in autoimmune hypoparathyroidism in the setting of isolated hypoparathyroidism or autoimmune polyglandular syndrome type 1. MATERIALS AND METHODS: A 34-year-old female presented with hypocalcaemia (6.0 mg/dL) and hypomagnesaemia (1.1 mg/dL) accompanied by low serum PTH (2.4 pg/mL) as well as urinary calcium and magnesium wasting. She was diagnosed with hypoparathyroidism, which was refractory to standard therapy. She was started on 60 mg prednisone and 150 mg azathioprine treatment daily on suspicion of an autoimmune aetiology. The patient was tested for CaSR antibodies. RESULTS: The patient was positive for CaSR antibodies of the IgG1 subtype, which stimulated phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and inositol phosphate (IP) accumulation. Post-treatment with prednisone and azathioprine, her serum calcium and magnesium normalized, as did her CaSR antibody titre and antibody-mediated stimulation of ERK1/2 phosphorylation and IP accumulation. CONCLUSION: This is the first demonstration of CaSR antibody-mediated hypoparathyroidism responsive to immunosuppressive therapy, adding to the evidence that autoimmune hypoparathyroidism can be, in some cases, reversible and not the result of autoimmune parathyroid destruction.

Presence of Autoreactive, MHC Class I-Restricted, Calcium-Sensing Receptor (CaSR)-Specific CD8+ T Cells in Idiopathic Hypoparathyroidism.

Context: Major histocompatibility complex class I allele HLA-A*26:01 and human leukocyte antigen (HLA) supertype A01 (STA01) are increased in idiopathic hypoparathyroidism (IH). However, cell-mediated autoimmune responses directed against the calcium-sensing receptor (CaSR) have not been demonstrated. Objective: To study CaSR-specific cytotoxic T-cell responses in peripheral blood mononuclear cells of IH patients. Design: Twenty-four peptides of CaSR (RH1 to RH24) were evaluated for their ex vivo potential to stimulate PBMCs from IH patients and controls in interferon (IFN)-γ enzyme-linked immunospot (ELISPOT) assays. Setting: Tertiary patient care center and National Institute of Immunology, New Delhi, India. Patients and Other Participants: Forty-five patients with IH attending the endocrine clinic of the All India Institute of Medical Sciences and 22 healthy controls. Main Outcome Measures: Major histocompatibility complex class-I restricted, CaSR-specific cytotoxic CD8+ T-cell responses evaluated by IFN-γ ELISPOT assay. Results: Of IH patients, 82.2% showed IFN-γ-secreting cells when stimulated ex-vivo with CaSR peptides. Peptides RH7, RH9, and RH16 elicited HLA supertype A01-restricted responses in IH. RH8, RH14, RH15, RH20, and RH21 peptides induced significantly higher responses in STA01+ IH patients compared with healthy controls irrespective of their supertype A01 status. Conclusions: Our ex vivo IFN-γ ELISPOT assays demonstrate the presence of CaSR-specific memory CD8+ T cells in the peripheral circulation of patients with IH, suggesting the role of cell-mediated autoimmune responses in the etiopathogenesis of IH.

Identification of autoimmune polyendocrine syndrome type 1 in patients with isolated hypoparathyroidism.

OBJECTIVE: The prevalence of autoimmune polyendocrine syndrome type 1 (APS1) among isolated hypoparathyroidism (HP) or primary adrenal insufficiency (PAI) is not well established. We studied the frequency of APS1 in patients with HP or PAI by measuring interferon-α (IFN-α) antibody levels, a highly sensitive and specific marker for APS1. DESIGN, PATIENTS AND MEASUREMENTS: In a single-centre cross-sectional study, 37 Indian patients with isolated HP and 40 patients with PAI were tested for IFN-α antibody using an indirect ELISA. In patients with elevated IFN-α antibody, the autoimmune regulator (AIRE) gene was bidirectionally sequenced. RESULTS: Three (8·1%) patients with isolated HP had elevated IFN-α antibody levels (range: 367-17382 units; positive titre >56 units). Homozygous or compound heterozygous AIRE mutations were detected in all three patients, including a novel mutation (p.T68P). All three APS1 patients had atypical features. The first patient, diagnosed at 7 years of age, died suddenly 5 months later. The second patient had late-onset HP (at the age of 34 years) and a solitary episode of transient mucocutaneous candidiasis 5 years later. The final patient developed HP at the age of 14 years and premature ovarian insufficiency 14 years later. Interleukin-22 antibodies, as well as most other organ-specific antibodies, were absent in the 3 APS1 patients. All patients with PAI were negative for IFN-α antibody. CONCLUSION: Eight percentage of patients with isolated HP had elevated IFN-α antibody levels and AIRE mutation-positive APS1. All APS1 patients had atypical clinical features. Testing for IFN-α antibody should be considered in patients with idiopathic HP.

Prevalence of coeliac disease in idiopathic hypoparathyroidism and effect of gluten-free diet on calcaemic control.

BACKGROUND: Patients with idiopathic hypoparathyroidism (IH) require variable doses of calcium and 1-α-(OH)D. The reasons for such variability are not clear. As autoimmune mechanisms may play a role in IH, there is a possibility of coexistent coeliac disease with calcium/vitamin D malabsorption. OBJECTIVE: We assessed the prevalence of coeliac disease and antitissue transglutaminase autoantibodies (anti-tTGAbs) in IH and analysed the effect of a gluten-free diet on calcaemic control. METHOD: A total of 171 patients with IH and 126 healthy controls were screened for anti-tTGAb. IH patients with anti-tTGAb >20 RU/ml underwent duodenoscopy and intestinal biopsy; those with biopsy-proven coeliac disease were followed up on a gluten-free diet. RESULTS: Eleven of 171 (6·4%) patients with IH and seven of 126 (5·6%) controls had anti-tTGAb (P = 0·81). There was no difference in the clinical and biochemical parameters at diagnosis and during long-term follow-up of 7·2 ± 4·8 year (mean serum total calcium = 1·88 ± 0·16 vs 1·82 ± 0·36 mmol/l, P = 0·52; phosphorus = 1·81 ± 0·17 vs 1·87 ± 0·36 mmol/l, P = 0·53) in IH patients with and without anti-tTGAb. Although CaSRAb positivity was comparable in the two groups, IH patients with anti-tTGAb had higher TPOAb positivity (45·5% vs 12·8%, P = 0·02). Coeliac disease was diagnosed in only 2/9 patients with IH on biopsy, both of whom showed improved calcaemic control with a gluten-free diet. CONCLUSION: The prevalence of coeliac autoimmunity (6·4%) and coeliac disease (1·2%) in patients with IH seems to be similar to that in the general population. Notwithstanding this modest prevalence, it is important to be aware of the potential occurrence of coeliac disease with IH and the beneficial effect of a gluten-free diet on calcium control.

Clinical and serologic parallels to APS-I in patients with thymomas and autoantigen transcripts in their tumors.

Patients with the autoimmune polyendocrine syndrome type I (APS-I), caused by mutations in the autoimmune regulator (AIRE) gene, and myasthenia gravis (MG) with thymoma, show intriguing but unexplained parallels. They include uncommon manifestations like autoimmune adrenal insufficiency (AI), hypoparathyroidism, and chronic mucocutaneous candidiasis plus autoantibodies neutralizing IL-17, IL-22, and type I IFNs. Thymopoiesis in the absence of AIRE is implicated in both syndromes. To test whether these parallels extend further, we screened 247 patients with MG, thymoma, or both for clinical features and organ-specific autoantibodies characteristic of APS-I patients, and we assayed 26 thymoma samples for transcripts for AIRE and 16 peripheral tissue-specific autoantigens (TSAgs) by quantitative PCR. We found APS-I-typical autoantibodies and clinical manifestations, including chronic mucocutaneous candidiasis, AI, and asplenia, respectively, in 49 of 121 (40%) and 10 of 121 (8%) thymoma patients, but clinical features seldom occurred together with the corresponding autoantibodies. Both were rare in other MG subgroups (n = 126). In 38 patients with APS-I, by contrast, we observed neither autoantibodies against muscle Ags nor any neuromuscular disorders. Whereas relative transcript levels for AIRE and 7 of 16 TSAgs showed the expected underexpression in thymomas, levels were increased for four of the five TSAgs most frequently targeted by these patients' autoantibodies. Therefore, the clinical and serologic parallels to APS-I in patients with thymomas are not explained purely by deficient TSAg transcription in these aberrant AIRE-deficient tumors. We therefore propose additional explanations for the unusual autoimmune biases they provoke. Thymoma patients should be monitored for potentially life-threatening APS-I manifestations such as AI and hypoparathyroidism.

Diagnosis and classification of autoimmune parathyroid disease.

Hypoparathyroidism (HP) is clinically characterized by the presence of hypocalcemia, usually associated with specific signs and symptoms that depend on how severe and chronic the disease becomes. HP is usually caused by surgical removal of all four parathyroids, while other forms are rarer. Autoimmune HP can occur as an isolated disease or as part of an autoimmune polyendocrine syndrome. Here we review what is known about parathyroid gland autoimmunity, focusing on recently-proposed parathyroid autoantibody markers, and particularly those directed against NACHT leucine-rich-repeat protein 5 and calcium-sensing receptor. We also describe the clinical characteristics of HP and design a diagnostic algorithm for autoimmune HP.

Immunological features of 22q11 deletion syndrome.

PURPOSE OF REVIEW: 22q11 deletion syndrome is the most common genetic abnormality. More patients are surviving cardiac surgery, and many do not have cardiac anomalies. Adult patients are now being described. It is important for paediatricians, and increasingly adult physicians, to be aware of the optimum management of these patients. RECENT FINDINGS: Three main immunological patterns are recognized, namely, athymic and incomplete 22q11 deletion syndrome and autoimmunity. Newborn screening for severe combined immunodeficiency detects athymic patients, although diagnosis may be complicated, and instructive cases are described. Incomplete 22q11 deletion syndrome is the most common presentation; new findings predict which patients are likely to experience significant infection. B lymphocyte deficiencies are often overlooked. Data regarding autoimmunity in adult patients is reported, as well as newly reported immunological findings. Finally, management guidelines are now published, and these are highlighted. SUMMARY: Newborn screening detects patients with athymic 22q11 deletion syndrome, but significant illness may complicate the picture, and dual diagnoses can confound treatment. Treatment options for these patients are becoming clearer. Hypoparathyroidism is associated with more severe infection, and immunoglobulin abnormalities are more common than previously recognized. Adult patients are symptomatic and management guidelines will help general physicians in managing these patients.

Calcium-sensing receptor autoantibodies and idiopathic hypoparathyroidism.

CONTEXT: Data on calcium-sensing receptor autoantibodies (CaSRAbs) in hypoparathyroidism are variable. OBJECTIVE: We assessed the prevalence and significance of CaSRAbs in idiopathic hypoparathyroidism. DESIGN: This was a case-control study. SUBJECTS: One hundred forty-seven patients with idiopathic hypoparathyroidism treated during 1998-2011 in a tertiary care setting and 348 controls [healthy, n = 199; type 1 diabetes mellitus (T1DM), n = 99; and chronic lymphocytic thyroiditis (CLT), n = 50] participated in the study. METHODS: CaSRAb assays included Western blot with CaSR protein expressed in Escherichia coli or human embryonic kidney (HEK)-293 cells, immunoprecipitation (IP) using in vitro-transcribed/translated protein, and indirect immunofluorescence on HEK293-CaSR. Functional significance was assessed by ERK1/2 phosphorylation. PTH and CaSR genes were sequenced for mutations. RESULTS: E coli-Western blot assay revealed 16.3% CaSRAb positivity in idiopathic hypoparathyroidism, which was comparable with healthy subjects and CLT but significantly less than the T1DM controls. The prevalence of CaSRAbs on HEK293-Western blot (24.5%) against 150 kDa and/or 168 kDa protein in hypoparathyroidism was significantly higher than the healthy subjects, T1DM, and CLT. IP assay showed CaSRAbs in 12.9% of the hypoparathyroid patients but not in controls. The sensitivity and specificity of CaSRAbs in E coli and HEK-293-CaSR Western blot and IP assays were 16.3% and 83.1%, 24.5% and 88.9%, and 12.9% and 100%, respectively, and 42.1% of the cases detected were common in the IP assay and HEK293-Western blot. Duration of illness and coexistent autoimmunity were similar in patients with and without CaSRAbs. The CaSRAb-positive sera showed no immunofluorescence and phosphorylated ERK1/2 activity. The CaSR gene sequence was normal in all patients. One of the patients showed a novel p.Met1_Asp6del mutation in the signal peptide region of the PTH gene. CONCLUSION: IP performed the best in detecting CaSRAbs in 12.9% of hypoparathyroid patients. Although CaSRAbs were functionally inert, its clinical relevance remains due to 100% specificity. Limited prevalence of CaSRAb suggests heterogeneity in the etiology of idiopathic hypoparathyroidism or the presence of CaSR epitopes other than those measured in the current study.

Prevalence and significance of NALP5 autoantibodies in patients with idiopathic hypoparathyroidism.

CONTEXT: Role of parathyroid autoimmunity in idiopathic hypoparathyroidism (IH) is not clear. Recently, parathyroid-specific NACHT leucine-rich-repeat protein 5 (NALP5) autoantibodies (Ab) have been reported in autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy syndrome. OBJECTIVE: Our objective was to assess prevalence and significance of NALP5 Ab in patients with IH. DESIGN AND SETTING: This was a case-control study at a tertiary care hospital. SUBJECTS: Subjects included 145 patients with IH recruited from 1998-2011 and 152 healthy controls. METHODS: Immunoprecipitation (IP) and Western blot (WB) assays were performed using ³5S-labeled NALP5 protein produced by in vitro transcription-translation and recombinant NALP5 protein in Escherichia coli, respectively. AIRE gene sequencing was performed in NALP5 Ab-positive patients. RESULTS: One of 145 patients (0.69%) and none of the 152 controls had NALP5 Ab on IP assay. Nine of 147 patients (6.12%) and four of 152 controls (2.63%) had NALP5 Ab on WB. One patient with NALP5 Ab on IP (36.6 sd score), also positive on WB, had a frameshift p.Ala386Serfs*38 AIRE gene mutation and adrenocortical Ab. Eight subjects with NALP5 Ab detected on WB had normal AIRE gene sequence. CONCLUSIONS: IP is currently the best assay to detect clinically relevant NALP5 Ab. Presence of NALP5 Ab in only one patient with IH who also had AIRE gene mutation suggests that these Ab are exceptionally rare in IH (0.69%) and, when present, occur in context of the autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy syndrome.

Genetics of hypoparathyroidism and pseudohypoparathyroidism.

Congenital hypoparathyroidism encompasses a series of disorders chracterized by the common biochimical feature of symptomatic hypocalcemia with concomitant hypophosphoremia. Clinical features differ among the various parathyroid-related hypocalcemic syndromes, as understandable on the basis of disorder-specific genetics. The present article reviews the various disorders related to both hypoparathyroid and pseudohypoparathyroid conditions, with a detailed report of the recent discoveries in term of the genetics of these syndromes.

Hypoparathyroidism and autoimmunity in the 22q11.2 deletion syndrome.

OBJECTIVE: To characterize the endocrine and autoimmune disturbances with emphasis on parathyroid dysfunction in patients with 22q11.2 deletion syndrome (22q11.2 DS). Design In this nationwide survey; 59 patients (age 1-54 years) out of 86 invited with a 22q11.2 DS were recruited through all the genetic institutes in Norway. METHODS: Data was collected from blood tests, medical records, a physical examination and a semi-structured interview. We registered autoimmune diseases and measured autoantibodies, hormone levels and HLA types. RESULTS: Twenty-eight (47%) patients had hypoparathyroidism or a history of neonatal or transient hypocalcemia. Fifteen patients had neonatal hypocalcemia. Fourteen patients had permanent hypoparathyroidism including seven (54%) of those above age 15 years. A history of neonatal hypocalcemia did not predict later occurring hypoparathyroidism. Parathyroid hormone levels were generally low indicating a low reserve capacity. Twenty-eight patients were positive for autoantibodies. Six (10%) persons had developed an autoimmune disease, and all were females (P<0.02). Hypoparathyroidism correlated with autoimmune diseases (P<0.05), however, no antibodies were detected against the parathyroid glands. CONCLUSIONS: Hypoparathyroidism and autoimmunity occur frequently in the 22q11.2 DS. Neonatal hypocalcemia is not associated with later development of permanent hypoparathyroidism. Hypoparathyroidism may present at any age, also in adults, and warrants regular measurement of calcium levels. Hypoparathyroidism and autoimmunity occur frequently together. Our findings of autoimmune diseases in 10% of the patients highlight the importance of stringent screening and follow-up routines.

AIRE gene mutations and autoantibodies to interferon omega in patients with chronic hypoparathyroidism without APECED.

OBJECTIVE: To assess autoimmune regulator (AIRE) gene mutations, class II HLA haplotypes, and organ- or non-organ-specific autoantibodies in patients with chronic hypoparathyroidism (CH) without associated Addison's disease (AD) or chronic candidiasis (CC). DESIGN, PATIENTS AND MEASUREMENTS: Twenty-four patients who had CH without AD or CC were included in the study. AIRE gene mutations in all 14 exons were studied using PCR in 24 patients, 105 healthy controls and 15 first-degree relatives of CH patients with AIRE mutations. Human leucocyte antigens (HLA) were determined for all 24 patients and 105 healthy controls. Autoantibodies to a range of antigens including NACHT leucine-rich-repeat protein-5 (NALP5) and interferon omega (IFNω) were tested in all 24 patients. RESULTS: AIRE gene mutations were found in 6 of 24 (25%) patients, all females, and this was significantly higher (P < 0·001) compared with AIRE mutations found in healthy controls (2/105). Three patients (12·5%) had homozygous AIRE mutations characteristic of Autoimmune-Poly-Endocrinopathy-Candidiasis-Ectodermal-Dystrophy and all three were also positive for IFNω-autoantibodies. Three patients (12·5%) had heterozygous AIRE mutations; two of these were novel mutations. One of the patients with heterozygous AIRE mutations was positive for both NACHT leucine-rich-repeat protein 5 and IFNω autoantibodies. Heterozygous AIRE mutations were found in 10 of 15 first-degree relatives of CH patients with AIRE mutations, although none was affected by CH. Class II HLA haplotypes were not statistically different in patients with CH compared to healthy controls. CONCLUSIONS: Analysis of AIRE gene mutations together with serum autoantibody profile should be helpful in the assessment of patients with CH, in particular young women with associated autoimmune diseases.

Association between hypoparathyroidism and defective T cell immunity in 22q11.2 deletion syndrome.

AIMS: Although poor thymic function leading to viral and fungal infections can be a feature of chromosome 22q11.2 deletion syndrome, most patients have relatively normal immunity. The aim of this study was to investigate which clinical and laboratory parameters best predict the likelihood of serious or recurrent infections in patients with this syndrome. METHODS: Clinical and laboratory parameters from 64 patients with 22q11.2 deletion syndrome referred to two immunology centres in the north of England were studied retrospectively. RESULTS: 31 (48%) patients had no problems with infection, 21 (33%) had bacterial infections, and 12 (19%) had recurrent or persistent thrush and/or viral enteritis and bronchiolitis, the latter suggestive of a significant T cell immunodeficiency. Patients with a history of thrush/viral infections, but not those with bacterial infections, had significantly lower CD4+ and CD8+ T lymphocyte numbers (relative risk (95% CI) 0.3 (0.1 to 0.8)) and phytohaemagglutinin mitogen responses (0.4 (0.2 to 0.8)) adjusted for age at testing. Hypoparathyroidism was associated with low T lymphocyte numbers and function (p<0.05) as well as an increased risk of thrush/viral infections (p<0.0001) after adjusting for age at testing. CONCLUSIONS: 22q11.2 syndrome patients with hypoparathyroidism are more likely to have a clinically significant T cell immunodeficiency and lower laboratory parameters of T cell function, with a higher risk of thrush and viral bronchiolitis and enteritis. Measurement of absolute CD3 count is a simple and accurate predictor of fungal/viral infection risk, with phytohaemagglutinin mitogen responses providing little or no further value in most patients.