Dominant suppression of Addison's disease associated with HLA-B15

Autoantibodies against Cytochrome P450 Side-Chain Cleavage Enzyme in Dogs (Canis lupus familiaris) Affected with Hypoadrenocorticism (Addison's Disease)

Canine hypoadrenocorticism likely arises from immune-mediated destruction of adrenocortical tissue, leading to glucocorticoid and mineralocorticoid deficiency. In humans with autoimmune Addison's disease (AAD) or autoimmune polyendocrine syndrome (APS), circulating autoantibodies have been demonstrated against enzymes associated with adrenal steroid synthesis. The current study investigates autoantibodies against steroid synthesis enzymes in dogs with spontaneous hypoadrenocorticism. Coding regions of canine CYP21A2 (21-hydroxylase; 21-OH), CYP17A1 (17-hydroxylase; 17-OH), CYP11A1 (P450 side-chain cleavage enzyme; P450scc) and HSD3B2 (3β hydroxysteroid dehydrogenase; 3βHSD) were amplified, cloned and expressed as 35S-methionine radiolabelled recombinant protein. In a pilot study, serum samples from 20 dogs with hypoadrenocorticism and four unaffected control dogs were screened by radio-immunoprecipitation assay. There was no evidence of reactivity against 21-OH, 17-OH or 3βHSD, but five dogs with hypoadrenocorticism showed immunoreactivity to P450scc compared with controls. Serum samples were subsequently obtained from 213 dogs diagnosed with hypoadrenocorticism and 110 dogs from a hospital control population. Thirty control dogs were randomly selected to establish a threshold for antibody positivity (mean + 3 × standard deviation). Dogs with hypoadrenocorticism were more likely to be P450scc autoantibody positive than hospital controls (24% vs. 1.2%, respectively; p = 0.0016). Sex was significantly associated with the presence of P450scc autoantibodies in the case population, with 30% of females testing positive compared with 17% of males (p = 0.037). Significant associations with breed (p = 0.015) and DLA-type (DQA1*006:01 allele; p = 0.017) were also found. This cross-sectional study indicates that P450scc autoantibodies are present in a proportion of dogs affected with hypoadrenocorticism.

Adrenal insufficiency

Adrenal insufficiency is the clinical manifestation of deficient production or action of glucocorticoids, with or without deficiency also in mineralocorticoids and adrenal androgens. It is a life-threatening disorder that can result from primary adrenal failure or secondary adrenal disease due to impairment of the hypothalamic-pituitary axis. Prompt diagnosis and management are essential. The clinical manifestations of primary adrenal insufficiency result from deficiency of all adrenocortical hormones, but they can also include signs of other concurrent autoimmune conditions. In secondary or tertiary adrenal insufficiency, the clinical picture results from glucocorticoid deficiency only, but manifestations of the primary pathological disorder can also be present. The diagnostic investigation, although well established, can be challenging, especially in patients with secondary or tertiary adrenal insufficiency. We summarise knowledge at this time on the epidemiology, causal mechanisms, pathophysiology, clinical manifestations, diagnosis, and management of this disorder.

Autoimmune polyglandular syndromes: interplay between the immune and the endocrine systems leading to a diverse set of clinical diseases and new insights into immune regulation

During the last 50 years, three major classes of autoimmune polyglandular syndromes (APSs) have been defined, and their characteristics and heritability have been delineated. Simultaneously, studies of the immunologic bases of these syndromes provided fundamental information in understanding immune regulation. Genetic analyses of patients and their families with APS type 1 (autoimmune polyendocrinopathy candidiasis, ectodermal dystrophy) identified the autoimmune regulator (AIRE) gene, which drives the expression of peripheral tissue-specific antigens in thymic cells and is critical in the development of self-tolerance. Mutations in this gene cause APS type 1. In contrast, studies in APS type 2 have been instrumental in understanding the role of human leukocyte antigen type II and related molecules in the pathogenesis of polygenetic autoimmune diseases such as type 1A diabetes. Immune dysfunction polyendocrinopathy, enteropathy, X-linked syndrome, which is caused by mutations in the forkhead box P3 gene, has been a model for studying regulatory T cell biology. The APSs epitomize the synergies that the merger of clinical and basic science can achieve. This is the environment that George Eisenbarth was able to create at the Barbara Davis Center for Diabetes.

[Subclinical adrenal diseases: silent pheochromocytoma and subclinical Addison's disease]

The silent pheochromocytoma, a hidden form of pheochromocytoma, exposes the patient to an increased risk of mortality if the diagnosis is not established on time. Biological diagnosis of pheochromocytoma can be difficult. Catecholamine secretion is dependent on tumor size and a large number of physiological, pharmacological, lifestyle modifications and sampling conditions influence the measurement of urinary and plasma metanephrines. The prevalence of pheochromocytoma is 2% among adrenal incidentaloma smaller than 3 cm (2/3 of tumors). Recent studies suggest the almost zero risk of pheochromocytoma among these tumors if they are hypodense (<10 housefield units) on adrenal tomography. Addison's disease is a pathology affecting about 1 in 8000. Immunopathology is still unknown, but some elements advocated the hypothesis of a predominant cell-mediated immunity in particular Interferon-gamma production by CD4 T lymphocytes in the presence of an epitope from the 21-hydroxylase, as well as IgG1 subtype produced by activated B lymphocytes, autoantibodies do appear to be a simple marker of the disease. Subclinical Addison's disease is defined by the presence of anti-21-hydroxylase autoantibodies, without clinical symptoms. It evolves faster to the clinical phase in young subjects, male, having high levels of autoantibodies and with an initially impaired adrenal function. Dosage of ACTH, plasma renin active, and basal cortisol and after Synacthen allow to discriminate the subjects with low or high risk of evolution and establish an appropriate monitoring.

Genetic determinants of 21-hydroxylase autoantibodies amongst patients of the Type 1 Diabetes Genetics Consortium

BACKGROUND

Autoantibodies to 21-hydroxylase (21OH-AA) precede the onset of autoimmune Addison's disease (AD) and are found in 1.5% of individuals with type 1 diabetes mellitus (T1DM). The greatest genetic risk for both disorders is found in the major histocompatibility complex (MHC), suggesting a common pathophysiology between AD and T1DM. Screening for 21OH-AA in newly diagnosed T1DM patients is a valuable prognostic tool, made stronger when MHC genotype is considered.

METHODS

The Type 1 Diabetes Genetics Consortium has collected genotype data in T1DM subjects with tissue-specific autoantibody typing. Genotype and phenotype data in individuals positive and negative for 21OH-AA are compared.

RESULTS

Major genetic risk for 21OH-AA is in the MHC haplotypes DRB1*04-DQB1*0302 (primarily DRB1*0404) and DRB1*0301-DQB1*0201. Protective effects in class II MHC haplotypes DRB1*0101-DQB1*0501 and DRB1*0701-DQB1*0202 also were detected. There is no difference in the presence of HLA-B15 and little difference in the presence of HLA-B8 (after class II effects are accounted for) in T1DM patients with 21OH-AA compared with known associations (HLA-B8 positive and HLA-B15 negative) in AD.

CONCLUSIONS

In 21OH-AA(+) subjects, genetic risk is found mainly in MHC class II haplotypes DR3 and DR4 but not class I alleles (HLA-B8 or HLA-B15). This suggests a difference between autoantibody formation (class II dependent) and progression to overt disease (class I dependent) in AD.

Predicting the onset of Addison's disease: ACTH, renin, cortisol and 21-hydroxylase autoantibodies

CONTEXT

Autoantibodies to 21-hydroxylase (21OH-AA) precede onset of autoimmune Addison's disease (AD). Progression to AD can take months to years, and early detection of metabolic decompensation may prevent morbidity and mortality.

OBJECTIVE

To define optimal methods of predicting progression to overt AD (defined by subnormal peak cortisol response to Cosyntropin) in 21OH-AA+ individuals.

DESIGN, SETTING AND PARTICIPANTS

Individuals were screened for 21OH-AA at the Barbara Davis Center from 1993 to 2011. Subjects positive for 21OH-AA (n = 87) were tested, and the majority prospectively followed for the development of Addison's disease, including seven diagnosed with AD upon 21OH-AA discovery (discovered), seven who progressed to AD (progressors) and 73 nonprogressors.

MAIN OUTCOME MEASURED

Plasma renin activity (PRA), ACTH, baseline cortisol, peak cortisol and 21OH-AA were measured at various time points relative to diagnosis of AD or last AD-free follow-up.

RESULTS

Compared with nonprogressors, in the time period 2 months-2 years prior to the onset of AD, progressors were significantly more likely to have elevated ACTH (11-22 pM, P < 1E-4), with no significant differences in mean PRA (P = 0·07) or baseline cortisol (P = 0·08), and significant but less distinct differences seen with 21OH-AA levels (P < 1E-4) and poststimulation cortisol levels (P = 6E-3).

CONCLUSION

Moderately elevated ACTH is a more useful early indicator of impending AD than 21OH-AA, PRA or peak cortisol, in the 2 months-2 years preceding the onset of AD.