THE THYMUS: EXPERIMENTAL PHYSIOLOGY,AND PATHOLOGY IN MAN

The thymus is an integral part of the immunological system. It is a site of intense lymphopoiesis, especially in early life. Neonatal thymectomy in mice causes runting and death due to gross immunological deficiencies. These deficiencies are determined by lymphopenia, and by lack of a lymphotrophic hormone secreted by the epithelial cells of the medulla; this hormone confers on lymphocytes the capacity to respond to antigenic stimulation. The thymus may be the main source of lymphoid cells carrying new or primary patterns of immune reactivity; it is thus “first-level” or “central” lymphoid tissue, which seeds cells to “second-level” or “peripheral” lymphoid tissues in the lymph nodes and spleen. Pathological lesions of the thymus in man include aplasia, hyperplasia, dysplasia and neoplasia. Gross aplasia characterizes the immunological deficiency diseases of infancy, including the lymphopenic type of congenital agammaglobulinæmia. Hyperplasia accompanies thyrotoxicosis. Dysplasia refers to the lymph follicle-germinal centre development in myasthenia gravis, probably an autoimmune disease, and to the proliferation in the medulla of spindle-epithelial cells in lupus erythematosus, an autoimmune disease. Neoplasia occurs as benign thymoma, which may be accompanied by extrathymic diseases which are possibly autoimmune in origin; these include myasthenia gravis, red cell aplasia, polymyositis, agammaglobulinæmia and lupus erythematosus. These diseases may in some way be caused by the thymoma; alternatively, the thymoma may represent the result of continuing hyperplasia of the thymus provoked by a primary autoimmune process. The place of thymectomy in the treatment of autoimmune disease is discussed. It is an established procedure in myasthenia gravis, and has been successful in two cases of autoimmune hæmolytic anæmia in infancy. We review our experience with thymectomy for three patients with systemic lupus erythematosus.     

Lupus érythémateux aigu systémique après thymectomie

Thymectomy has a broad indication for the treatment of myasthenia gravis. Occurrence a few months or years after thymectomy of a number of autoimmune diseases including systemic lupus erythematosus in myasthenic patients is very rare. We report a 51-year-old woman who developed a systemic lupus 1 year after the thymectomy.     

Concomitant polymyositis and myasthenia gravis reveal malignant thymoma. A case report and review of the literature.

The frequency of thymona associated with autoimmune diseases has been reported to be increased, with 50% of thymoma patients also having myasthenia gravis (MG). Other autoimmune disorders, such as autoimmune erythroblastopenia and polymyositis (PM), have been less frequently associated with thymoma. The association of MG and PM with thymoma is rare. We here report the case of a 66-year-old woman whose concomitant MG and PM revealed malignant thymoma and review the other published cases of this association.     

Acute systemic lupus erythematosus after thymectomy for myasthenia. Sequential study of lymphocyte subpopulations

A 35 year-old woman developed severe systemic lupus erythematosus 9 years after thymectomy for myasthenia gravis. "Seric Thymic Factor" (STF) was low; T helpers subset, T helpers/T suppressors ratio and to a lesser extent T suppressors subset were decreased. Suppressor cell function investigated by Concanavaline A lymphocyte reactivity was low. Under cyclophosphamide, plasmapheresis and steroids all clinical and biological symptoms improved but STF remained low; T helpers, T suppressors subsets and T helpers/T suppressors ratio increased but did not reach the normal range. Statistical and immunological arguments suggest that the association between systemic lupus erythematosus and myasthenia gravis did not occur only by chance. Moreover, thymectomy might have played a role by decreasing the number and function of some subpopulations of lymphocytes.     

Multiple autoimmune syndromes

The possibility of three or more autoimmune diseases occurring in the same patient cannot be fortuitous and suggests a pathogenic relationship between each of them. In the light of 4 personal cases, the authors have recorded 87 reports of such associations in the literature, an analysis of which leads them to propose a classification of three types of multiple autoimmune syndrome. The grouping of these syndromes under a single heading should make the research and analysis of these morbid associations easier. Moreover, the classification adopted by the authors allows a more precise definition of patients with at least two autoimmune diseases and so helps to recognize the onset of a third autoimmune disease at a later date. Multiple autoimmune syndromes can be classified in 3 groups according to the prevalence of their associations one with another. Type I comprises myasthenia, thymoma, polymyositis and giant cell myocarditis, this association having a single pathogenic mechanism. Type II includes the Sj?gren's syndrome, rhumatoid arthritis, primary biliary cirrhosis, scleroderma and autoimmune thyroid disorders. Type III groups together 10 autoimmune diseases (autoimmune thyroid disease, myasthenia and/or thymoma, Sj?gren's syndrome, pernicious anaemia, idiopathic thrombocytopaenic purpura, Addison's disease, insulin-dependent diabetes, vitiligo, autoimmune haemolytic anaemia, systemic lupus erythematosus) for which a genetic predisposition (phenotype HLA B8 and/or DR3 or DR5) seems to be an important factor.     

A case of systemic lupus erythematosus complicated by pure red cell aplasia and idiopathic portal hypertension after thymectomy

We describe a 49-year-old woman who presented in 2002 with pure red cell aplasia (PRCA), systemic lupus erythematosus (SLE), and idiopathic portal hypertension (IPH) that developed following a thymectomy. She underwent a thymectomy at 40 years of age to treat myasthenia gravis. PRCA developed 3 years after the thymectomy and she was successfully treated with cyclosporin. Systemic lupus erythematosus and IPH were diagnosed 6 years later. We conclude that immunological dysfunction resulting from the thymectomy contributed significantly to the subsequent development of PRCA, SLE, and IPH in this patient. This is the first report to describe this extremely rare occurrence.     

Circulating proteasomes are markers of cell damage and immunologic activity in autoimmune diseases

OBJECTIVE: The 20S proteasome plays a leading immunologic role in the cytosolic generation of MHC class I restricted antigens, and it represents an abundant antigen in several autoimmune diseases. To investigate the effects of autoimmune inflammatory and perioperative traumatic cellular damage, we determined qualitative and quantitative properties of released proteasomes (circulating proteasomes, cProteasomes) from serum samples of patients with a variety of autoimmune diseases. METHODS: cProteasomes were analyzed from serum samples of 314 patients with several systemic and organ-specific autoimmune diseases and 85 healthy controls. The concentrations of cProteasomes were determined by sandwich ELISA using a monoclonal and a polyclonal proteasome-specific antibody. Followup analyses were performed in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) as well as in patients with myasthenia gravis undergoing thoracoscopic thymectomy. RESULTS: Strongly increased levels of cProteasomes (> 1000 ng/ml) were detected in samples obtained from patients with autoimmune myositis, SLE, primary Sj?gren's syndrome, RA, and autoimmune hepatitis. Significant differences were observed in the mean values of cProteasomes comparing systemic with organ-specific autoimmune diseases. Followup analyses revealed a close correlation of cProteasome with the autoimmune process as well as cellular damage. Moreover, cProteasomes were isolated in intact and native as well as in degraded or dissociated forms from the serum samples. The immuno-subunit LMP7 was found to be incorporated in the circulating protease complex. CONCLUSION: Levels of cProteasomes are markedly elevated in patients with systemic autoimmune diseases, apparently correlating with disease activity. The cProteasomes represent novel sensitive markers of the autoimmune inflammatory processes and/or reflect the magnitude of cellular damage.     

A case of systemic lupus erythematosus complicated by pure red cell aplasia and idiopathic portal hypertension after thymectomy

Abstract

We describe a 49-year-old woman who presented in 2002 with pure red cell aplasia (PRCA), systemic lupus erythematosus (SLE), and idiopathic portal hypertension (IPH) that developed following a thymectomy. She underwent a thymectomy at 40 years of age to treat myasthenia gravis. PRCA developed 3 years after the thymectomy and she was successfully treated with cyclosporin. Systemic lupus erythematosus and IPH were diagnosed 6 years later. We conclude that immunological dysfunction resulting from the thymectomy contributed significantly to the subsequent development of PRCA, SLE, and IPH in this patient. This is the first report to describe this extremely rare occurrence.     

Early recurrence or persistence of autoimmune diseases after unmanipulated autologous stem cell transplantation

Autologous stem cell transplantation with or without in vitro lymphocyte depletion has been suggested as a new treatment option for severe autoimmune diseases. We describe five patients with autoimmune diseases (CREST syndrome, myasthenia gravis and Hashimoto's thyroiditis, systemic lupus erythematosus, atopic dermatitis, and rheumatoid arthritis) who underwent autologous bone marrow (n = 1) or peripheral blood progenitor cell (n = 4) transplantation with unmanipulated grafts as treatment for the autoimmune disease in one case or as treatment for a malignant disorder with a concomitant autoimmune disorder in four cases. In all patients serological and clinical signs of the autoimmune disease recurred early or persisted. These observations should be regarded as a cautionary note concerning the efficacy of high-dose therapy followed by transplantation of unmanipulated autologous stem cells for treatment of severe autoimmune diseases.     

La myasthénie du côté de l’interniste

Myasthenia gravis is an autoimmune disease due to specific antibodies inducing a neuromuscular transmission defect causing muscle fatigability. If onset of the disease may be at any age, myasthenia gravis concerns mostly young adults, in majority females. The disease characteristic features are the following: ocular symptoms (ptosis or diplopia) as main initial manifestation, extension to other muscles in 80 % of the cases, variability of the deficit, effort induced worsening, successive periods of exacerbation during the disease course, severity depending on respiratory and swallowing impairment (if rapid worsening, a myasthenic crisis is to be suspected), association with thymoma in 20 % of patients and with other various autoimmune diseases, most commonly hyperthyroidism and Hashimoto's disease. Diagnosis relies on the clinical features, improvement with cholinesterase inhibitors, detection of specific autoantibodies (anti-AChR or anti-MuSK), and significant decrement evidenced by electrophysiological tests. The points concerning specifically the internist have been highlighted in this article: diagnostic traps, associated autoimmune diseases, including inflammatory myopathies that may mimic myasthenia gravis, adverse effects of medications commonly used in internal medicine, some of them inducing myasthenic syndromes. The treatment is well codified: the treatment is well codified: (1) respect of adverse drugs contra-indications, systematically use of cholinesterase inhibitors, (2) thymectomy if thymoma completed with radiotherapy if malignant, (3) corticosteroids or immunosuppressive agent in severe or disabling form, (4) intensive care unit monitoring, plasmapheresis or intravenous immunoglobulins for patients with myasthenic crisis.     

A sequence of pathologic events in a patient after thymectomy for myasthenia gravis

The case of a rare coexistence of myasthenia gravis (MG) with systemic lupus erythematosus (SLE) is described. MG was diagnosed prior to SLE which developed after thymectomy. The patient was affected by HCV viremia. Therefore, there were therapeutic problems. Metylase treatment was continued for several years and dopamine receptor agonist was effectively administered as adjunctive therapy in SLE.     

A patient with thymoma and four different organ-specific autoimmune diseases

This is the first report of a patient with four organ-specific autoimmune diseases; myasthenia gravis, type 1 diabetes mellitus, autoimmune hepatitis and Hashimoto's thyroiditis. The clinical history suggests a relationship with a non-removed thymoma. Not only the thymoma seems to have triggered these four diseases, the dramatic progressive course with an active autoimmune hepatitis and high concentrations of multiple autoantibodies was probably also associated with non-removal of the thymoma. Thymectomy should be performed in myasthenia gravis patients with thymoma and associated autoimmune diseases.     

A pair of monozygotic twins who are concordant for myasthenia gravis but became discordant for systemic lupus erythematosus post-thymectomy

We describe a pair of monozygotic twins who are concordant for myasthenia gravis but discordant for systemic lupus erythematosus (SLE). SLE developed in twin 1 18 years post-thymectomy and has been characterized by recurrent transverse myelitis and optic neuritis. Twin 2 remains well post-thymectomy, except for a skin rash and persistent leukopenia. Both twins have developed autoimmune thyroid disease. We review genetic and environmental factors of importance in the pathogenesis of SLE and discuss the possible role of thymectomy in the etiology of the disease.     

Malignant thymoma associated with myasthenia gravis, Graves' disease, and SIADH

Patients with thymoma are likely to present with associated autoimmunologic disorders. The occurrence of syndrome of inappropriate antidiuretic hormone (SIADH) attributable to thymoma is extremely rare. We herein present an extremely rare case of a 59-year-old man patient who was discovered to have malignant thymoma associated with myasthenia gravis, Graves' disease, and SIADH. He was admitted for evaluation and treatment of hyponatremia (Na 125 mEq/l). SIADH was diagnosed, and thymoma was identified as its cause. The patient was also found to have both Graves' disease and myasthenia gravis. The hyponatremia was normalized with water restriction and 3% saline therapy before thymectomy. The thymic tumor was a Masaoka stage III thymoma that resulted in direct invasion to the wall of the innominate vein, but there was no finding of invasion to other mediastinal organs. Complete thymectomy with innominate vein graft was performed. Microscopic histopathology findings corresponded to those of a mixed-type thymoma and type B2. However, immunohistochemical stain for antidiuretic hormone was negative in the tumor cells. Adjuvant radiation therapy was employed postoperatively, and the patient's postoperative recovery was uneventful. He subsequently reached a euthyroid state. And the reversal to normal sodium and osmolality levels was continued after the tumor removal without any further management for hyponatremia. The observation of this interesting case and a literature review provided us with the opportunity to explore the pathogenesis and clinical aspects of thymoma-related autoimmune and/or endocrine disorders which must be suspected in patients with thymoma.     

Gm and Km allotypes in autoimmune diseases.

The associations or linkages between the polymorphisms of the Gm and Km immunoglobulin allotypes and the susceptibility to autoimmune diseases, including diseases with immuno-pathological pathogenesis are reported in this review. These diseases include multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, insulin-dependent diabetes mellitus, Crohn's disease, coeliac disease, Graves' disease, atrophic thyroiditis, Hashimoto's thyroiditis, myasthenia gravis, chronic active hepatitis, alopecia areata, uveitis, vitiligo, Turner's syndrome, glomerular nephritis, Berger's disease and idiopathic dilated cardiomyopathy. Immunoglobulin allotypes are described as well as the statistical methods used to analyse the data.     

Obstetric complications due to autoantibodies

Autoimmune diseases are most common and most active in young women; it is therefore not uncommon for obstetricians and physicians to encounter pregnant women with these conditions, and knowledge of the potential maternal, foetal and neonatal complications is essential for good clinical management. The most common maternal autoimmune endocrine conditions in pregnancy are insulin-dependent diabetes mellitus and thyroid disease. Other relatively common non-endocrine autoimmune conditions include systemic lupus erythematosus and anti-phospholipid syndrome. Much rarer autoimmune conditions include autoimmune thrombocytopenia, rheumatoid arthritis, myasthenia gravis and Addison's disease. In this chapter, we discuss autoimmune endocrine conditions and briefly mention some non-endocrine conditions of particular importance.     

Coexistence of systemic lupus erythematosus and myasthenia gravis: two distinct populations of anti-DNA and anti-acetylcholine receptor antibodies

A woman with a four-year history of systemic lupus erythematosus (SLE) developed myasthenia gravis (MG). The clinical features of lupus disappeared slowly while the myasthenic syndrome became predominant. However, her serum was positive for anti-DNA and anti-acetylcholine receptor antibodies. Cross-reactivity between anti-DNA antibodies and anti-acetylcholine receptor antibodies was not demonstrated, suggesting the presence of two different populations. A cellular immunology profile was normal as expected in MG and in contrast to SLE. Conceivably, SLE and MG might represent two opposite extremes in the spectrum of autoimmune diseases.     

Association of neuromyelitis optic (NMO) with autoimmune disorders: report of two cases and review of the literature

We present two patients with neuromyelitis optica (NMO; Devic’s syndrome), one associated with systemic lupus erythematosus and the other with Hashimoto thyroiditis. Devic’s syndrome, whose initial symptoms and signs mimic those of multiple sclerosis, can be associated with other autoimmune diseases. We emphasize the importance of ruling out other entities throughout the follow-up. NMO is seldom described in patients with lupus, which may be due to the rare occurrence of this association sometimes leading to its misdiagnosis.     

Mapping of multiple susceptibility variants within the MHC region for 7 immune-mediated diseases

The human MHC represents the strongest susceptibility locus for autoimmune diseases. However, the identification of the true predisposing gene(s) has been handicapped by the strong linkage disequilibrium across the region. Furthermore, most studies to date have been limited to the examination of a subset of the HLA and non-HLA genes with a marker density and sample size insufficient for mapping all independent association signals. We genotyped a panel of 1,472 SNPs to capture the common genomic variation across the 3.44 megabase (Mb) classic MHC region in 10,576 DNA samples derived from patients with systemic lupus erythematosus, Crohn''s disease, ulcerative colitis, rheumatoid arthritis, myasthenia gravis, selective IgA deficiency, multiple sclerosis, and appropriate control samples. We identified the primary association signals for each disease and performed conditional regression to identify independent secondary signals. The data demonstrate that MHC associations with autoimmune diseases result from complex, multilocus effects that span the entire region.