A ring-calcified thymoma, mimicking pericardial cyst, precedes pure red cell aplasia for more than 10 years - A case-based overview of pathophysiology

Pure red cell aplasia (PRCA) is a rare disease characterised by anaemia and low reticulocyte count, caused by absence of erythropoiesis in the bone marrow. This report describes a case of a ring-calcified thymoma that led to the development of PRCA. Moreover, we provide an overview on the classification of thymoma and the pathophysiology and treatment of PRCA.

Sclerosing thymoma: A rare case report and brief review of literature

RATIONALE

Sclerosing thymoma is an extremely rare mediastinal neoplasm; it was recognized for the first time in 1994 and to date only 15 cases have been reported.

PATIENT CONCERNS

The present study report a case of a 65-year-old man who was incidentally found to have an anterior mediastinal nodule, without clinical symptoms including fever, chest pain, and myasthenia gravis.

DIAGNOSES

The chest computed tomography (CT) revealed the nodule was 4.9 × 4.2 × 3.0 cm in size. And the microscopic and immunohistochemical findings indicated that the final diagnosis was sclerosing thymoma.

INTERVENTIONS

The anterior mediastinal nodule was completely removed.

OUTCOMES

No evidence of recurrence or complication was found in the second year after surgery.

LESSONS

The biologic behavior of the rare sclerosing thymoma is still largely mysterious; it is utmost importance to classify the sclerosing thymoma from other mediastinal tumors. Its prognosis is favorable and thymectomy is currently the mainstay of treatment.

Thymic large cell neuroendocrine carcinoma - a rare and aggressive tumor: a case report

BACKGROUND

Neuroendocrine tumors are a large group of tumors with a wide spectrum of behavior, affecting mainly the digestive system and the lung. The thymus is very rarely affected.

CASE PRESENTATION

A 28-year-old Arab woman presented with chronic chest pain and dyspnea. A computed tomography scan showed a huge anterior mediastinal mass invading neighboring structures. A mediastinotomy was performed with biopsies of the mass. Pathological findings were consistent with a thymic large cell neuroendocrine carcinoma.

CONCLUSIONS

The occurrence of a large cell neuroendocrine carcinoma in the thymus, especially in young people, is extremely rare. In this current report, we discuss the clinicopathological issues of this rare tumor according to recent literature data.

Nephrotic syndrome associated with metastatic thymoma treated with chemotherapy

RATIONALE

Nephropathy with concurrent invasive thymoma is a type of paraneoplastic syndrome.

PATIENT CONCERNS AND DIAGNOSES

We report a 32-year-old female with nephrotic syndrome that was first diagnosed along with invasive thymoma and treated by means of cisplatin-based chemotherapy for the thymoma. The patient initially presented with dyspnea and generalized edema. Chest radiography and computed tomography scans revealed right pleural effusion and a mass in the right middle lung field, which were confirmed by a percutaneous lung biopsy as metastatic invasive thymoma. Severe hypoalbuminemia, heavy proteinuria, hyponatremia, and hypercholesterolemia were features of the nephrotic syndrome. A kidney needle biopsy suggested focal segmental glomerulosclerosis.

INTERVENTIONS AND OUTCOMES

All of the symptoms of nephrotic syndrome were resolved simultaneously during the first 2 cycles of chemotherapy. The patient was on regular follow-up with no specific treatment for nephrotic syndrome and underwent successful resection of the left pleura and anterior thymoma. The patient has shown no evidence of recurrence for 2 years.

LESSONS

We conclude that chemotherapy for invasive thymoma is an effective treatment for nephrotic syndrome accompanying the thymoma.

Lupus Nephritis with Thymoma Managed by Thoracoscopic Surgery and Prednisolone

A 48-year-old woman was admitted to our hospital to undergo evaluation for fatigue, severe weight loss, and nephrotic range proteinuria. Light microscopy of a renal biopsy specimen revealed class III (A) lupus nephritis, while immunofluorescence and electron microscopy only showed sparse immune deposits with findings that were not typical of lupus nephritis. Computed tomography revealed a mass in the anterior mediastinum, which was resected. The examination of the surgical specimen revealed type A noninvasive thymoma. In combination with thymomectomy, postoperative steroid therapy achieved the prompt remission of lupus nephritis. In this patient, thymoma-related autoimmunity may have contributed to the exacerbation of lupus nephritis.

Postoperative Recurrence of Invasive Thymoma with Cold Agglutinin Disease and Autoimmune Hemolytic Anemia

A 50-year-old man presented to our hospital in 1995. Invasive thymoma was diagnosed and extended thymectomy and left upper lobe partial resection were performed. In 2013, he complained of dyspnea. Chest computed tomography showed postoperative recurrence of invasive thymoma. Several chemotherapies were administered. Severe anemia and an increase in the total bilirubin level were observed with chemotherapies. In additional, an examination showed that the direct Coombs test was positive. Cold agglutinin was also high. We herein experienced a rare case of postoperative recurrence of invasive thymoma with cold agglutinin disease and autoimmune hemolytic anemia.

Thymoma and paraneoplastic myasthenia gravis

Paraneoplastic autoimmune diseases associate occasionally with small cell lung cancers and gynecologic tumors. However, myasthenia gravis (MG) occurs in at least 30% of all patients with thymomas (usually present at MG diagnosis). These epithelial neoplasms almost always have numerous admixed maturing polyclonal T cells (thymocytes). This thymopoiesis-and export of mature CD4(+)T cells-particularly associates with MG, though there are rare/puzzling exceptions in apparently pure epithelial WHO type A thymomas. Other features potentially leading to inefficient self-tolerance induction include defective epithelial expression of the autoimmune regulator (AIRE) gene and/or of major histocompatibility complex class II molecules in thymomas, absence of myoid cells, failure to generate FOXP3(+) regulatory T cells, and genetic polymorphisms affecting T-cell signaling. However, the strong focus on MG/neuromuscular targets remains unexplained and suggests some biased autoantigen expression, T-cell selection, or autoimmunization within thymomas. There must be further clues in the intriguing serological and cellular parallels in some patients with late-onset MG but without thymomas-and in others with AIRE mutations-and in the contrasts with early-onset MG, as discussed here.

Chronic cough in thymoma

Cough is one of the most common symptom for which patients seek medical attention from primary care physicians and pulmonologists. Although tuberculosis and other lung infections are common throughout the developing world, they are not among the most common causes of chronic cough. We report a case of a 23 years old male who presenting to the outpatient clinic with chronic cough not responding to regular and symptomatic treatment that was diagnosed to have thymoma. After all the common causes for chronic cough have been ruled out, unusual causes should also be considered in the differential diagnosis.

A case of autoimmune thyroiditis and membranoproliferative glomerulonephritis

Thyroid hormones play an important role in the growth of the kidney and maintenance of its functions. Prolonged hypothyroidism is known to be accompanied by changes in renal morphology such as thickening of the glomerular and tubular basement membranes as well as increased mesangial matrix. Increased transcapillary leakage of plasma proteins leading to proteinuria and generalized edema is also a known complication of hypothyroidism. In particular, autoimmune thyroiditis is associated with proteinuria. Most previous reports of autoimmune thyroiditis with nephrotic syndrome have demonstrated mixed pathological morphology marked by predominant membranous glomerulopathy. Here we present a patient whose initial presentation with profound hypothyroidism and autoimmune thyroiditis was dominated by nephrotic syndrome secondary to type 1 membranoproliferative glomerulonephritis (MPGN). The association of MPGN and autoimmune thyroiditis is very rare.

Malignant thymoma and myasthenia gravis presenting as polymyositis: a case report

Polymyositis revealing myasthenia gravis and malignant thymoma: a case report. The increased frequency of thymoma associated with autoimmune diseases has been well documented in the literature. However the association of polymyositis (PM) and myasthenia gravis (MG) revealing a malignant thymoma is rare. We report a case of a gentleman whose presenting symptoms were those of polymyositis.

[Clinical and electrophysiological characteristics of myasthenia gravis with thymoma: analysis of 72 patients]

OBJECTIVE

To investigate the clinical and electrophysiological characteristics of myasthenia gravis with thymoma (MGT).

METHODS

The clinical and repetitive nerve stimulation (RNS) data of 72 patients with MGT, 36 males and 36 females, and 63 patients with myasthenia gravis without thymoma (NMGT) were analyzed retrospectively.

RESULTS

The onset age of 52 of the 72 MGT patients (72.2%) was 35-59. The average onset age of the MGT patients was 39.5, older than that of the NMGT patients (29.4 yrs), and the course of the MGT patients was 13.1 months, shorter than that of the NMGT patients (29.1 months)The attack rate of the males was not significantly different than that of the females. The proportion of generalized presentation type among the MGT patients was 72.8%, higher than that among the NMGT patients (66.7%), particularly concerning the respiratory muscle (20.8% vs. 9.5%). The average time interval between the onset of symptoms and respiratory or bulbar muscle involvement of the NMGT patients were 12 and 7 months respectively, both remarkably shorter than those of the NMGT patients (26.4 and 11.6 months respectively). The abnormal RNS test yield rate of the MGT patients was 86.9%, higher than, however, not significantly that of the NMGT patients (75.0%). 97.2% of the thymoma and mediastinal abnormality could be detected through computed tomography (CT) scan on thymus. The positive rate of AchRab titer of the MGT patients was 50.0%, not significantly different from that of the NMGT patients (52.4%).

CONCLUSION

MGT is common in middle-aged people, both male and female. The Course is quickly progressive and generalized skeletal muscles, particularly respiratory muscles, are more involved in the MGT patients than in the NMGT patients. RNS study is a sensitive tool to identify MGT. AchRab may not be the specific antibody for recognizing MGT. CT scan is useful in differentiating thymoma preoperatively.

Muscle lymphocytic infiltrates in thymoma-associated myasthenia gravis are phenotypically different from those in polymyositis

The aim of the study is to provide evidence that the lymphocytic infiltration of myasthenia gravis (MG) muscle do not represent a true autoimmune myositis, rather an infiltration by naive lymphocytes derived from lymphocyte-rich thymomas. Muscle biopsies from 179 patients with pure MG, 6 thymoma patients without MG and 15 patients with definite polymyositis were analyzed. In 18 patients with MG (all associated with lymphocyte-rich thymomas) and in two thymoma patients without MG, lymphocytic infiltrates were identified in muscles. By use of immunohistochemistry, we demonstrated that the lymphocytes in MG differ from those in polymyositis, being mature but in contrast to polymyositis naive CD45RA+ T lymphocytes. We suggest that the lymphocytic infiltrates in patients with MG and thymoma represent an infiltration of muscle by thymoma-derived mature but naive T cells. The finding of CD8+CD45RA+ lymphocytes in muscle may signify an underlying thymoma and should not be misdiagnosed as polymyositis.

Prosthetic replacement and tangential resection of the superior vena cava in chest tumors

AIM

Infiltration of the superior vena cava (SVC) due to advanced non small cell lung cancer (NSCLC) or thymoma can be treated by prosthetic replacement or tangential resection. These two technical procedures and their results are described.

METHODS

From 1988 to 2002, we performed 37 SVC resections: 21 replacements with polytetrafluoroethylene (PTFE) prostheses and 16 tangential exereses. Sixteen patients affected by locally advanced NSCLC (12 T4; 4 extracapsular N2) and 5 subjects with thymoma (Stage III Masaoka) underwent prosthetic replacement of the SVC. After neoadjuvant polychemotherapy, tangential resection was performed on 12 patients with extracapsular N2 NSCLC, and in 1 patient with T4 and in 3 patients with T3a disease. We performed prosthetic replacement in 18 cases using a straight prosthesis (?18-20 mm). A bridge (10-14 cm) between the innominate vein and the right atrium was created in 3 patients. The main indication for a prosthetic replacement was infiltration of more than 30% of the circumference of the SVC. There were 4 thromboembolic complications (19%), with one intraoperative death (4.8%). Tangential resection of the SVC for infiltration <20% was performed both manually and with staplers (double clamping) without any major complications.

RESULTS

Mean survival was 23 months in those patients who had undergone PTFE replacement for T4 lung cancer and for thymoma. Mean survival was 15 months in those who had undergone tangential resections for NSCLC with extracapsular N2. We performed restaging of the tumor using chest angio-CT scan in 11 patients, one year after the operation. We found 80% patency in 7 SVC prostheses and 50% patency in 4 others: the two bridges between the left innominate vein and the right atrium appeared to be partially closed but were compensated by important collateral circles.

CONCLUSION

SVC replacement, associated with pulmonary resection or removal of mediastinal masses, can be performed in selected cases. It should not be considered as palliative treatment because of the important perioperative risks. SVC tangential resection involves fewer surgical problems. However, since this procedure is used mostly for N2 NSCLC subjects, patients have a low mean survival in spite of adjuvant therapy.

Is excitation–contraction coupling impaired in myasthenia gravis?

OBJECTIVE

To investigate whether excitation-contraction (E-C) coupling of muscle is impaired in patients with myasthenia gravis (MG).

METHODS

In 51 patients with generalized MG and 35 normal subjects, compound muscle action potentials (CMAPs) of the abductor pollicis brevis, and movement-related potentials using an accelerometer placed at the thumb tip were simultaneously recorded after median nerve stimulation at the wrist. The E-C coupling time (ECCT) was estimated by a latency difference between CMAP and movement-related potential. Antibodies against acetylcholine receptor (AChR), ryanodine receptor (RyR), and muscle specific receptor tyrosine kinase (MuSK) were measured by immunoassays.

RESULTS

The mean ECCT was significantly longer in patients with MG (mean+/-SEM; 2.79+/-0.1 ms; p=0.002) than in normal controls (2.52+/-0.1 ms). Among MG patients, the mean ECCT was longer for patients with thymoma than for those without it (P=0.04), and was shorter for patients treated with FK506 (an immunosuppressant and also an enhancer of RyR related Ca(2+) release) than for those not receiving this treatment (p=0.04). ECCT had no significant correlation with anti-AChR, anti-RyR, or anti-MuSK antibodies.

CONCLUSIONS

In MG, E-C coupling appears to be impaired, particularly in patients with thymoma, and FK506 possibly facilitates E-C coupling.

SIGNIFICANCE

The functional implication of impaired E-C coupling is not established, but it may contribute to muscle weakness in patients with MG.

Paraneoplastic diseases associated with thymoma

BACKGROUND

Thymoma is frequently associated with paraneoplastic diseases (PDs), most commonly with myasthenia gravis (MG). This association is thought to depend on thymoma's capacity to produce and export T lymphocytes.

OBJECTIVE

(1) To determine the frequency and characteristics of thymoma-associated PDs other than MG; (2) to evaluate T cell maturation in thymomas with and without PDs.

METHODS

We studied 260 patients with thymoma (associated with MG in 228). The occurrence of PDs was monitored together with the tumor outcome. Phenotypic characterization of thymocyte subsets in 14 thymoma samples (7 with and 7 without MG) was performed by FACS.

RESULTS

A total of 47 PDs was diagnosed in 41/260 patients (15.8 %). Neurological PDs included neuromyotonia, limbic encephalitis, polymyositis, subacute hearing loss, psychosis and sleep disorders. A broad spectrum of nonneurological PDs were observed, among these, hematological and cutaneous diseases prevailed. Like MG, these disorders occurred either in the presence of the thymoma or at different times after thymomectomy; their onset often heralded a tumor recurrence. In thymomas from MG subjects, we found an increased proportion of fully mature CD4 single positive (SP) thymocytes and a reduced frequency of CD4SPCD25(+) cells; the latter finding may reflect a deficient generation of T regulatory cells, a reduced intratumorous activation of T cells, or both.

CONCLUSIONS

We confirm the strong association of thymoma with PDs. These disorders often occurred in MG patients and their course in relation to thymoma was similar to that of MG. In accordance with previous observations, we found some alterations in the intratumorous production of mature CD4(+) T cells that could be involved in the pathogenesis of paraneoplastic autoimmunity.

Myasthenia gravis and sevoflurane--a case report

Myasthenia gravis is characterized by weakness and easy fatiguability of voluntary muscles. Myasthenic patients are sensitive to non-depolarizing relaxants. Sevoflurane, as an alternative, can be used to achieve good tracheal intubation. In this report, we present our experiences.

Raised prolactin levels in myasthenia gravis: two case reports and a study of two patient populations

OBJECTIVES

To describe two patients with myasthenia gravis (MG) and prolactinoma and analyze the associations between MG and prolactin (PRL) levels.

DESIGN

Two case reports and a case-control study of PRL levels in 192 patients with MG.

PARTICIPANTS

The Immunological Research Laboratory, Center for Molecular Medicine, Department of Medicine and the Department of Neurology, Karolinska Institutet, Stockholm, Sweden; St Petersburg Medical Academy for Postgraduate Studies, and St Petersburg State Medical Pediatric Academy, Russia.

RESULTS

Two women with MG and thymic hyperplasia accompanied by prolactinomas are described. The levels of plasma PRL were raised in 101 women with MG, but not in 91 men. There was an association between high PRL levels and high levels of autoantibodies against the acetylcholine receptor.

CONCLUSIONS

There is an association of MG with raised levels of PRL in women. PRL has stimulating effects on immune activation and the increased levels might thus be implied in the pathophysiology of MG.

Voltage-gated potassium channel antibodies associated limbic encephalitis in a patient with invasive thymoma

Recently, limbic encephalitis (LE) associated with Voltage-gated potassium channel antibody (VGKC-Ab) has been postulated as a new autoimmune disorder. Most previously reported cases of VGKC-Ab-associated LE were non-paraneoplastic, and reports of a paraneoplastic type are rare. Here we describe a 59-year-old woman with paraneoplastic VGKC-Ab-associated LE preceding the recurrence of invasive thymoma. There was a close temporal relationship between the clinical course and the changes of the VGKC-Ab titer. Unlike many of the non-paraneoplastic VGKC-Ab-associated LE cases, our cases showed the more extensive high intensity lesions on MRI and the absence of seizure and hyponatremia.

Acetylcholine receptor antibodies in myasthenia gravis are associated with greater risk of diabetes and thyroid disease

OBJECTIVE

Myasthenia gravis (MG) may be associated with the presence of acetylcholine receptor antibodies (AChRAb) [seropositive MG (SPMG)] or their absence [seronegative MG (SNMG)]. Along with features of MG, the presence of the AChRAb may relate to the existence of other immune-mediated diseases. We sought to determine the association of SPMG with other potential autoimmune diseases.

METHODS

A retrospective evaluation of prospectively identified MG patients at a tertiary care center was performed, with patients separated into SPMG and SNMG. Prevalence of other immune-mediated disorders, as well as the epidemiology, sensitivity of diagnostic testing, and thymic pathology, was contrasted between both patient groups.

RESULTS

Of the 109 MG patients identified, 66% were SPMG. SPMG was associated with a greater likelihood of significant repetitive stimulation decrement, the presence of either thymoma or thymic hyperplasia, and the presence of thyroid disease. In addition, all patients with a diagnosis of diabetes, concurrent with MG, were found to be SPMG.

CONCLUSIONS

AChRAb and SPMG impart not only a distinctive clinical and electrophysiological phenotype of MG, but are also associated with the heightened presence of endocrinological disease.

Myasthenia gravis in children: a longitudinal study

BACKGROUND

Juvenile myasthenia gravis (JMG) is an uncommon disease. Unlike adults, clinical characteristics and outcomes of myasthenia gravis (MG) are not well studied in children.

PATIENTS AND METHODS

Case records of 77 patients with MG who were 15 years of age or less at disease onset, evaluated over a period of 34 years at the National Institute of Mental Health and Neurosciences, Bangalore, India, were reviewed. Their clinical characteristics and response to therapy was compared with 290 patients with MG onset after 15 years of age.

RESULTS

Median age at onset was 8 years and mean period of follow-up was 6.2 years (range 6 months to 25 years). At presentation, 30% of patients had ocular myasthenia and the rest had generalized disease. Twenty-one patients (27%) had disease confined to ocular muscles throughout the course and three had limb girdle myasthenia. Familial myasthenia was more common than adult onset disease, 10 patients had positive family history. Unlike adults, none of the patients had associated autoimmune disease. Fifty-two patients (67%) received corticosteroids, and azathioprine was added in five patients. Thymectomy was performed in 11 patients, six below the age of 15 years. Thymic histology was normal in one and showed hyperplasia in eight and thymoma in one. Four patients had crisis. At the end of follow-up, 25 patients were asymptomatic, 28 had partial improvement, and nine remained unchanged or worsened and two died. Ten patients achieved complete stable remission.

CONCLUSIONS

This study shows some distinctive characteristics of JMG, such as higher frequency of ocular myasthenia, benign course, better long-term outcome and lack of association of thymoma and other autoimmune disorders.

Sequential antibodies to potassium channels and glutamic acid decarboxylase in neuromyotonia

A patient with thymoma-associated neuromyotonia and voltage-gated potassium channel (Kv1.2 and Kv1.6) antibodies by immunoprecipitation and rat brain immunolabeling was treated successfully with immunoadsorption and cyclophosphamide. Curiously, glutamic acid decarboxylase antibodies, absent at onset, appeared later. Stiff-person syndrome was absent, but fast blink reflex recovery suggested enhanced brainstem excitability. The range of antibodies produced in thymoma-associated neuromyotonia is richer, and the timing of antibody appearance more complex, than previously suspected.

Perivascular infiltrate of memory lymphocytes and mature dendritic cells in MG thymomas

In thymomas associated with myasthenia gravis (MG), the authors found that perivascular infiltrates of memory lymphocytes and mature dendritic cells (DCs) were more frequent in patients with early improvement after thymectomy than in patients without response to thymectomy. Although these findings may be limited to particular types of thymoma, thymectomy may interrupt the recruitment of mature DCs in thymus and export of activated T cells to extra-thymic tissues, thereby improving the disease.

Thymoma-associated neuromyotonia with antibodies against voltage-gated potassium channels presenting as chronic intestinal pseudo-obstruction

Chronic intestinal pseudo-obstruction can occur as a paraneoplastic disorder, and several cases have been reported in association with thymoma or small-cell lung cancer. Autoantibodies against voltage-gated potassium channels (VGKCs) are found in acquired neuromyotonia (Isaac's syndrome), and have been reported in one case of slow transit constipation without apparent neurological disease. We describe a patient with VGKC antibodies, acquired neuromyotonia and thymoma, who first presented with a severe slow-transit constipation and in whom the gastrointestinal symptoms responded well to plasmapheresis. We suggest that VGKC antibodies might be helpful in patients with possible paraneoplastic chronic intestinal pseudo-obstruction, and a positive result should stimulate the search for a thymoma or other tumour and raise the possibility of immunotherapy.

Thymic carcinoma: a clinicopathological and immunohistological study of 19 cases

AIMS

To study 19 cases of primary thymic carcinoma in order to define the clinicopathological features and the precise histochemical profile of this rare and heterogeneous group of tumours of the anterior mediastinum.

METHODS AND RESULTS

The study group consisted of 13 males and six females, with a mean age of 58.5 years (range 29-75 years). Superior vena cava syndrome and chest pain were the main presenting symptoms. Three patients were asymptomatic. No patient had myasthenia gravis. Six different histological types were identified: neuroendocrine tumours (six patients), epidermoid carcinoma (five patients), sarcomatoid carcinoma (three patients), lymphoepithelioma-like carcinoma (two patients), mucoepidermoid carcinoma, clear cell carcinoma, and undifferentiated carcinoma (one patient each). The clear cell carcinoma was associated with a thymic cyst. No association with thymoma was observed. Surgical resection, performed in 10 cases, was complete in two. Sixteen patients received thoracic radiation, and 11 received systemic chemotherapy. Follow-up information was available in 16 cases; 12 patients presented with local or metastatic relapse, and 10 patients died of their tumour. The overall 5-year survival was 14.5%.

CONCLUSION

Primary thymic carcinoma is a very heterogeneous group of tumours of the anterior mediastinum with an aggressive clinical behaviour, and a poor overall prognosis.

Overexpression of IL-7Rα provides a competitive advantage during early T-cell development

Critical checkpoints controlling early thymic T-cell development and homeostasis are set by the proper signaling function of the interleukin 7 receptor (IL-7R) and the pre–T-cell antigen receptor. Although αβ T-cell development is observed in IL-7– and IL-7Rα–deficient mice, the number of thymocytes is significantly reduced, implying a role for the IL-7R in controlling the size of the thymic T-cell compartment. Here, we report the overexpression of IL-7Rα that occurs in the early T-cell compartment from AKR/J mice, animals that are highly susceptible to the spontaneous development of thymoma. Increased IL-7Rα was revealed by surface staining, and increased IL-7Rα mRNA was documented by using reverse transcriptase–polymerase chain reaction (RT-PCR). This resulted in increased survival of AKR/J early thymocytes, shown by the decreased frequency of TUNEL+ (terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate [dUTP]–fluorescein nick end labeling) cells. In an in vivo thymocyte repopulation model, AKR/J thymocytes had a selective advantage over healthy thymocytes. This advantage occurred at early stages of T-cell development. Our findings support the model that overexpression of growth factor receptors can contribute to proliferation and malignancy.

Syndrome of inappropriate secretion of antidiuretic hormone due to malignant thymoma

The authors present the case of a 51-year-old female with a syndrome of inappropriate secretion of antidiuretic hormone (SIADH) due to a malignant thymoma. Laboratory examinations of the patient showed hyponatremia, plasma hypoosmolarity in the presence of concentrated urine and normal urine excretion of sodium. CT revealed a mass lesion in the mediastinum. A biopsy of the mediastinal mass was performed and the diagnosis of thymoma with SIADH was established. This is a rare description of a malignant thymoma associated with SIADH.

[Erythropoiesis disorders and other central autoimmune anemias]

Immune-mediated acquired disorders of erythropoiesis can result in pure red cell aplasia or ineffective erythropoiesis. Erythropoiesis can be suppressed or impaired by humoral or cellular mechanisms. In vitro inhibition of erythroid colony growth by humoral factors or lymphocytes is a strong argument for the immune origin of the disease. Classical aetiologies are thymoma and hematological malignancies such as chronic lymphocytic leukaemia. Clonal proliferation of T cells has also been incriminated. Recently, acquired circulating autoantibodies directed against erythropoietin have been detected in a case of pure red cell aplasia. Autoimmune mechanisms have also been suggested in two dyserythropoietic syndromes recently described.

Limbic encephalitis associated with recurrent thymoma: a postmortem study

The authors report an autopsied patient with limbic encephalitis and recurrent thymoma. The immunohistochemical study showed selective depositions of immunoglobulin G on the neurons in the limbic system and the tumor cells of the recurrent thymoma. The immunoblotting study detected two types of antibodies that react with the human brain, rat brain, and rat thymus.

A 25-year thymoma treatment review

Most thymomas are stage I or II at presentation, and they have a good prognosis with surgical treatment. Higher stage thymomas are less common and their treatment is more problematic. Our center tends to attract patients with higher stage thymomas for treatment. We reviewed our experience and contrasted it with other published series. A 25-year retrospective record review of thymomas was done. 38 patients were treated. Median age was 49 years. Four had myasthenia gravis. Masaoka staging was: stage I--9; stage II--6; stage III--15; stage IVa--4; stage IVb--4. Resection was done in 25 patients (21 had R0 resection), chemotherapy was given to 15 patients, and 27 patients received radiotherapy. Overall median survival was 55 months. Overall 5 and 10-year survivals were 30% and 18%. 5-year survival by stage was: stage I--75%; stage II--50%; stage III/IV--23%. Negative prognostic factors on univariate analysis included presence of symptoms at presentation (p = 0.02), unresectable tumor (p = 0.06), stage III/IV (p = 0.04), and disease recurrence after resection (p = 0.0001). On multivariate analysis, only stage (p = 0.04) and recurrence (p = 0.0001) were independent predictors of survival. All patients who recurred after resection eventually died of disease. Our overall treatment results are disappointing, but we had higher stage patients than reported by most other centers. Early stage thymomas are suitable for complete surgical resection, and the prognosis is favorable. However, higher stage thymomas (stage III and higher) pose problems for complete surgical resection and their prognosis is poor. Newer multimodality treatment approaches are indicated for higher stage thymomas.

Myasthenia, thymoma, presynaptic antibodies, and a continuum of neuromuscular hyperexcitability

BACKGROUND

Autoantibodies specific for the nicotinic acetylcholine receptor (AChR) of skeletal muscle impair neuromuscular transmission in myasthenia gravis (MG). Autoantibodies specific for alpha3 neuronal AChRs or voltage-gated potassium channels have been reported in patients with Isaacs syndrome, an acquired disorder of continuous muscle fiber activity characterized by neuromyotonia.

OBJECTIVE

To report the neuromuscular autoantibody profiles of three patients with a syndrome of MG and neuromuscular hyperexcitability.

RESULTS

All three patients reported here had clinical and electrophysiologic evidence of MG and neuromuscular hyperexcitability. None had neuromyotonia. Thymoma was proven in two patients and suspected in the third. One had MG and thymoma and subsequently developed cramp-fasciculation syndrome; MG and rippling muscle syndrome appeared simultaneously in the other two. All patients had muscle and neuronal AChR binding antibodies and striational antibodies. Only one had antibodies reactive with alpha-dendrotoxin-complexed potassium channels.

CONCLUSIONS

The coexistence of cramp-fasciculation syndrome and acquired rippling muscle syndrome with MG, thymoma, and neuronal AChR autoantibodies suggests that there is a continuum of autoimmune neuromuscular hyperexcitability disorders related pathogenically to Isaacs syndrome. Manifestations of neuromuscular hyperexcitability may be altered and less apparent in the context of MG because of the coexisting defect of neuromuscular transmission.

Polymyositis with respiratory muscle weakness requiring mechanical ventilation in a patient with metastatic thymoma treated with octreotide

Although most patients with thymoma present with a mediastinal mass amenable to surgical resection, some patients develop metastatic disease requiring systemic therapy. The majority of thymomas express somatostatin receptors as demonstrated by octreotide scanning, an observation which has prompted the clinical use of octreotide in patients with this disease. Many patients with thymoma exhibit autoimmune paraneoplastic syndromes, most frequently myesthenia gravis. We report here the case of a patient with metastatic thymoma who developed a profound autoimmune polymyositis and lupus-like syndrome that flared following treatment with octreotide and was associated with a clinical response to this agent. No evidence for myesthenia gravis was discovered. The severity of the myopathy necessitated mechanical ventilation for 12 weeks. The natural history of thymoma, treatment options including recent combination chemotherapy regimens, and potential mechanisms for flaring of autoimmune paraneoplastic syndromes triggered by therapy of thymoma are discussed.

TNFA and TNFB polymorphisms in myasthenia gravis

BACKGROUND

Tumor necrosis factor (TNF) alpha and TNF-beta are proinflammatory cytokines thought to be involved in the pathogenesis of myasthenia gravis (MG).

OBJECTIVE

To examine whether TNF polymorphisms are associated with MG, MG subgroups, and the presence of titin and ryanodine-receptor antibodies.

PATIENTS AND METHODS

We did genotyping on 30 patients with MG and 92 healthy blood donors for 2 biallelic TNFA polymorphisms (G to A at positions -238 and -308) and 1 TNFB polymorphism (NcoI digestive site) using methods based on the polymerase chain reaction.

RESULTS

Patients with thymoma were typically homozygous for both the TNFA*T1 and the TNFB*2 alleles, but patients having an early onset of MG without thymoma were carriers of the TNFA*T2 and TNFB*1 alleles. Patients without thymoma who had the titin antibody had the same high frequency of TNFA*T1 and TNFB*2 as patients with thymoma, whereas patients without the titin antibody carried the same allele, TNFA*T2 and TNFB*1, regardless of age and thymic disease. No association was found with acetylcholine-receptor levels or disease severity for any of the TNFA or TNFB polymorphisms.

CONCLUSION

Patients having MG, including those with thymoma, who have the titin antibody are most often homozygous for the TNFA*T1 and TNFB*2 alleles, whereas the presence of the TNFA*T2 and TNFB*1 alleles correlates with early-onset MG and the absence of titin antibodies.

Ectopic expression of E47 or E12 promotes the death of E2A-deficient lymphomas

Mice with null mutations in the E2A gene are highly susceptible to the spontaneous development of thymic lymphomas. To understand better how E2A deficiency may contribute to lymphomagenesis, we have observed the consequences of enforced expression of the E2A gene products E12 and E47 in cell lines derived from lymphomas that arose spontaneously in E2A-deficient mice. E2A-expressing cells are steadily eliminated from lymphoma cultures into which E47 or E12 was introduced. The mechanism underlying the loss of E2A-expressing cells does not involve an arrest in cell-cycle progression. Rather, the E2A proteins activate a programmed cell death pathway in these lymphomas. This E2A-mediated cell death appears to be preceded by a loss of mitochondrial transmembrane potential. These data provide direct evidence that E2A gene products can act as tumor suppressors.

Influence of age on extended thymectomy as a treatment for myasthenia gravis

This retrospective study examines the influence of age on extended thymectomy as a treatment for myasthenia gravis. From 1979 to 1997, 58 patients with myasthenia gravis underwent extended thymectomy at Miyazaki Medical College Hospital. We used the onset age of the disease to divide these patients into two groups: Group A included 14 patients >/= 50 years of age; Group B, 44 patients < 50. Using Osserman's classification and the duration of the disease prior to hospitalization, we observed no significant differences between the two groups although thymoma were more prevalent in Group A. All 58 patients underwent extended thymectomy, with no surgical mortalities. The mean duration of tracheal intubation after thymectomy for Group A was 6.25 days; for Group B, 4.66 days without statistically significant differences between both groups. Using Masaoka's criteria, we evaluated the clinical course of myasthenia gravis following extended thymectomy for each of the 58 patients. The remission rates in Groups A and B were 28.6% and 29.5%, respectively; the improvement rates, 71.4% and 79.5%, respectively with no significant differences among groups. These findings suggest that the clinical course of myasthenia gravis following extended thymectomy is not age-dependent and that extended thymectomy is a clinically safe and effective treatment option for myasthenia gravis patients >/= 50 years of age.

[Hypophyseal-adreno-gonadal system function in myasthenia patients with tumorous and nontumorous pathology of the thymus]

Overall twenty-five patients (all women) who ranged from 16 to 56 years old were examined. They were divided into two groups: group I was formed of subjects with hyperplasia of the thymus gland, group II--thymoma. Blood serum levels of prolactin, progesterone, estriol, estradiol, testosterone hydrocortisone. All patients showed a significant increase in average blood plasma levels of estrogens, testosterone and prolactin. Average levels of progesterone and hydrocortisone in patients with thymus hypertrophy were lower than in controls, while in thymoma patients these were much higher. The data submitted are indicative of substantial differences in the endocrine status of myasthenia patients depending on tumor or nontumor lesion of the thymus gland, which fact may suggest different pathogenetic mechanisms of development of the condition.

A pathogenetic role for the thymoma in myasthenia gravis. Autosensitization of IL-4- producing T cell clones recognizing extracellular acetylcholine receptor epitopes presented by minority class II isotypes

Myasthenia gravis (MG) is caused by helper T cell-dependent autoantibodies against the muscle acetylcholine receptor (AChR). Thymic epithelial tumors (thymomas) occur in 10% of MG patients, but their autoimmunizing potential is unclear. They express mRNAs encoding AChR alpha and epsilon subunits, and might aberrantly select or sensitize developing thymocytes or recirculating peripheral T cells against AChR epitopes. Alternatively, there could be defective self-tolerance induction in the abundant maturing thymocytes that they usually generate. For the first time, we have isolated and characterized AChR-specific T cell clones from two MG thymomas. They recognize extracellular epitopes (alpha75-90 and alpha149-158) which are processed very efficiently from muscle AChR. Both clones express CD4 and CD8alpha, and have a Th-0 cytokine profile, producing IL-4 as well as IFN-gamma. They are restricted to HLA-DP14 and DR52a; expression of these minority isotypes was strong on professional antigen-presenting cells in the donors' tumors, although it is generally weak in the periphery. The two clones' T cell receptor beta chains are different, but their alpha chain sequences are very similar. These resemblances, and the striking contrasts with T cells previously cloned from non-thymoma patients, show that thymomas generate and actively induce specific T cells rather than merely failing to tolerize them against self antigens.

A new mouse gene, SRG3, related to the SWI3 of Saccharomyces cerevisiae, is required for apoptosis induced by glucocorticoids in a thymoma cell line

We isolated a new mouse gene that is highly expressed in thymocytes, testis, and brain. This gene, SRG3, showed a significant sequence homology to SWI3, a yeast transcriptional activator, and its human homolog BAF155. SRG3 encodes 1,100 amino acids and has 33-47% identity with SWI3 protein over three regions. The SRG3 protein contains an acidic NH2 terminus, a myb-like DNA binding domain, a leucine-zipper motif, and a proline- and glutamine-rich region at its COOH terminus. Rabbit antiserum raised against a COOH-terminal polypeptide of the SRG3 recognized a protein with an apparent molecular mass of 155 kD. The serum also detected a 170-kD protein that seems to be a mouse homologue of human BAF170. Immunoprecipitation of cell extract with the antiserum against the mouse SRG3 also brought down a 195-kD protein that could be recognized by an antiserum raised against human SWI2 protein. The results suggest that the SRG3 protein associates with a mouse SWI2. The SRG3 protein is expressed about three times higher in thymocytes than in peripheral lymphocytes. The expression of anti-sense RNA to SRG3 mRNA in a thymoma cell line, S49.1, reduced the expression level of the SRG3 protein, and decreased the apoptotic cell death induced by glucocorticoids. These results suggest that the SRG3 protein is involved in the glucocorticoid-induced apoptosis in the thymoma cell line. This implicates that the SRG3 may play an important regulatory role during T cell development in thymus.

Sex hormones and the thymus in relation to thymocyte proliferation and maturation

This paper reviews the mechanism of sex hormone actions on the thymus, presenting mainly our data obtained at the cellular and molecular levels. First, data supporting the "genomic" action via the nuclear sex hormone receptor complexes are as follows: 1) sex hormone receptors and the thymic factor (thymulin) are co-localized in thymic epithelial cells, but not in T cells; 2) production/expression of thymic factors (thymulin, thymosin alpha 1) are remarkably inhibited by sex hormone treatment; 3) sex hormones cause changes in T cell subpopulations in the thymus; and 4) sex hormones strongly influence the development of thymus tumors in spontaneous thymoma BUF/Mna rats through their receptor within the tumor cells. Secondly, data indicating the "non-genomic" action of sex hormones via a membrane signal-generating mechanism are as follows: 1) the proliferation/maturation of thymic epithelial cells is mediated through protein kinase C activity introduced by sex hormones; 2) sex hormones directly influence DNA synthesis and cdc2 kinase (cell cycle-promoting factor) activity.

Prognostic factors of patients with thymoma

OBJECTIVES

To analyze the prognostic factors influencing the survival of patients with thymoma, clinical characteristics, treatment modalities and survival of patients were evaluated. The efficacy of chemotherapy was also determined.

METHODS

Retrospective study was done on one hundred patients whose diagnosis was confirmed pathologically at Seoul National University Hospital from 1981 to 1994. The staging was carried out according to the Masaoka system. Survival rate was calculated by the Kaplan-Meier method and prognostic factors were analyzed by a multivariate analysis (Weibull model).

RESULTS

The stage of 100 patients was as follows: Stage I-50, II-6, III-27, IV A-10, IV B-7. The overall survival rates at 5 and 10 years after diagnosis were 73.1% and 58.7%, respectively. The 5-year survival differences, according to various prognostic factors, were as follows: 1) Stage: I-92.8%, II-100%, III-71.6%, IVA-25.9% and IVB-32.9% (p = 0.0029). 2) Age: < 60 years-79.5% and > or = 60 years-41.5% (p = 0.0489). 3) Extent of resection: Total patients: complete resection-87.6% and incomplete resection-50.5% (p > 0.05) Stage III: complete resection-66.7% and incomplete resection-75.5% (p > 0.05) 4) Myasthenia gravis: present-71.6% and absent-74.9% (p > 0.05) Seventeen patients were treated with a combination chemotherapy of Cyclophosphamide, Adriamycin and cisplatin(CAP). Two complete responses and seven partial responses (overall response rate of 53%) were observed with a median response duration of fourteen months. Combination chemotherapy with CAP was effective.

CONCLUSIONS

Stage and age were the independent prognostic factors in patients with thymoma. However, the presence of myasthenia gravis or the extent of resection in stage III patients was not associated with the survival time.