Thymoma, Myasthenia Gravis, and Other Paraneoplastic Syndromes

Multiple paraneoplastic syndromes: myasthenia gravis, vitiligo, alopecia areata, and oral lichen planus associated with thymoma

Thymomas are associated with paraneoplastic autoimmune diseases at a high frequency. It is rare that four paraneoplastic autoimmune disorders co-occur in a single patient. We describe a thymoma patient with diagnoses of myasthenia gravis, vitiligo, alopecia areata, and oral lichen planus associated with a thymoma. After thymectomy, the weakness, vitiligo, alopecia and mucocutaneous lesions were improving progressively, possibly implicating the thymoma in initiating these autoimmune conditions. We believe that this is the first report of this particular combination of multiple paraneoplastic syndromes associated with thymoma.

Metaplastic thymoma of the mediastinum. A clinicopathologic, immunohistochemical, and genetic analysis

Metaplastic thymoma is a rare primary thymic epithelial tumor, and its biologic behavior is uncertain. We report 7 cases of metaplastic thymoma. The spindle components of the tumor seemed to be undergoing epithelial-mesenchymal transition, which is characterized by the loss of E-cadherin expression. Epstein-Barr virus seemed not to have an etiologic role in metaplastic thymoma. No gross genetic alterations were found by using comparative genomic hybridization. The patients were alive and well in follow-up ranging from 11 to 172 months (mean, 81.7 months). The findings suggest that metaplastic thymoma has a benign clinical course. Unless the histomorphologic findings show malignant features, surgical excision alone is recommended.

Preliminary results of VATS thymectomy for pediatric myasthenia gravis

Myasthenia gravis (MG) is a debilitating disease which necessitates long-term medical therapy. If left untreated, it can have a high mortality rate. The commonest variety in children, the autoimmune variety, often requires recourse to immunomodulation including prolonged usage of high-dose steroids. Thymectomy has not been a popular option among treating clinicians. There is evidence to suggest that if thymectomy is performed early in the disease, it has a high success rate in reducing the doses of the oral steroid medication and also in inducing remission of the disease. We have performed video-assisted thoracoscopic surgery (VATS) thymectomy in four patients with the autoimmune variety of MG. In this study, we have had a fair and comparable success rate as with the other adult series. On the basis of this preliminary study, we recommend that the option of VATS thymectomy should be offered to select patients of MG.

Myasthenia gravis in dogs with an emphasis on treatment and critical care management

OBJECTIVE

To review the human and veterinary literature on the pathophysiology of myasthenia gravis (MG) and describe treatment options for clinical use in people and animals.

DATA SOURCES

Human and veterinary clinical reports, studies and reviews, textbooks, and recent research findings in MG from 1996 present, with a focus on treatment and patient management.

HUMAN DATA SYNTHESIS

MG is a well-described condition in people with new research and treatment options available. Many of the newest therapeutic options available in veterinary medicine for MG are based on current strategies used in people with this condition. Seronegative MG is well described in people and provides insight to clinical cases encountered in veterinary medicine when the index of suspicion is high though serologic tests are negative.

VETERINARY DATA SYNTHESIS

Previous studies in veterinary medicine focused on the use of acetylcholinesterase inhibitors as the main form of treatment in canine MG. Recent studies, mainly case series and case reports, emphasize the use of immunomodulatory treatments as an alternative for long-term treatment. However, there are no randomized, controlled studies on treatment with immunomodulatory therapy for MG in dogs available to assess the efficacy of this treatment strategy.

CONCLUSIONS

Although early recognition of clinical signs is most important in the outcome of patients with MG, further understanding the pathophysiology of MG may lead to earlier diagnosis and novel treatment strategies. The discovery of additional autoantibodies against striated muscle proteins in dogs, should enhance our understanding of diseases affecting the neuromuscular junction. In addition, clinical data for canine MG could be applied to other autoimmune disorders.

Anticytokine autoantibodies in infectious diseases: pathogenesis and mechanisms

Autoantibodies to cytokines occur in many different conditions and situations and can cause a wide range of disease, including pulmonary alveolar proteinosis, disseminated non-tuberculous mycobacterial disease, pure red-cell aplasia, and chronic mucocutaneous candidiasis. Anticytokine autoantibodies may also develop against exogenously administered cytokines, sometimes diminishing their effects or inhibiting the activity of the endogenous cytokine. Unlike primary congenital immunodeficiencies, autoantibodies may develop over time, wax and wane, and may change in titre or avidity. Naturally occurring autoantibodies to interferons α, β, and γ, interleukins 1α, 2, 6, and 10, tumour necrosis factor, and granulocyte-macrophage colony-stimulating factor have been reported in healthy individuals and have been identified in rheumatological diseases, graft-versus-host disease, and cancer. Therapeutic antibodies, growth factors, other biological agents, and cytokines used to treat acute, chronic, malignant, and immune diseases may elicit or overcome autoantibodies, hence influencing the primary intended therapy. The increasing number of biologically active anticytokine autoantibodies being reported suggests that currently "idiopathic" diseases may someday be explained by neutralising or agonising autoantibodies. Their protean roles in causing, treating, preventing, and responding to disease, as well as simply maintaining normal homoeostasis, offer fascinating insights into the biology of immunity, inflammation, and infection.

Mechanisms underlying autoimmune synaptic encephalitis leading to disorders of memory, behavior and cognition: insights from molecular, cellular and synaptic studies

Recently, several novel, potentially lethal and treatment-responsive syndromes that affect hippocampal and cortical function have been shown to be associated with auto-antibodies against synaptic antigens, notably glutamate or GABA-B receptors. Patients with these auto-antibodies, sometimes associated with teratomas and other neoplasms, present with psychiatric symptoms, seizures, memory deficits and decreased levels of consciousness. These symptoms often improve dramatically after immunotherapy or tumor resection. Here we review studies of the cellular and synaptic effects of these antibodies in hippocampal neurons in vitro and preliminary work in rodent models. Our work suggests that patient antibodies lead to rapid and reversible removal of neurotransmitter receptors from synaptic sites, leading to changes in synaptic and circuit function that in turn are likely to lead to behavioral deficits. We also discuss several of the many questions raised by these and related disorders. Determining the mechanisms underlying these novel anti-neurotransmitter receptor encephalopathies will provide insights into the cellular and synaptic bases of the memory and cognitive deficits that are hallmarks of these disorders, and potentially suggest avenues for therapeutic intervention.

Rituximab for the treatment of thymoma-associated and de novo myasthenia gravis: 3 cases and review

OBJECTIVES

Myasthenia gravis (MG) is an immune-mediated disorder associated with autoantibodies against postsynaptic nicotinic acetylcholine receptors at neuromuscular junctions. Rituximab, a monoclonal antibody specific for CD20, is used primarily to treat B-cell non-Hodgkin lymphoma. Although it has been used for treatment of a number of autoimmune diseases, there is limited experience in MG.

METHODS

Three patients with refractory MG (2 with concurrent thymoma) were given rituximab.

RESULTS

Symptoms stabilized and reductions in immunosuppressive medications were tolerated for extended periods, without adverse effects or infectious complications.

CONCLUSIONS

These observations support the concept that rituximab may be helpful for the treatment of MG. Remissions in patients with or without thymoma are achievable with rituximab given in combination with commonly used modalities. Furthermore, rituximab is not necessarily contraindicated for the treatment of MG in patients being treated for thymoma. Controlled studies are called for to define its role in the treatment of refractory MG.

Treatment of advanced thymoma and thymic carcinoma

Although thymic epithelial tumors are rare, they are relatively common among neoplasms of the anterior superior mediastinum. They usually exhibit indolent behavior, but do have the capacity to invade surrounding structures and metastasize to distant sites. Thymic carcinomas are rare, but are highly aggressive tumors that are associated with a poor prognosis. The mainstay of therapy is complete surgical resection. Locally advanced thymoma and thymic carcinoma require a multimodality treatment approach with a combination of surgery, chemotherapy, and radiation therapy to decrease the chances of recurrence and improve survival. The risk of disease recurrence lasts for a number of years after completion of primary therapy. A majority of cases of recurrent disease present as pleural recurrences. Once again, surgical resection of recurrent disease represents the cornerstone of successful therapy and is critical to long-term survival. In recent years, a better understanding of the biologic basis of thymic epithelial tumors has led to the emergence of targeted therapy directed against this malignancy.