Thymolipoma associated with myasthenia gravis

Thymolipoma-associated Myasthenia Gravis with High Titer of Anti-MuSKAb: A Case Report

Myasthenia gravis (MG) is a neuromuscular junction disorder caused by pathogenic autoantibodies to some parts of the post-synaptic muscle endplates. About 85% of generalized MG patients have autoantibodies against post-synaptic acetyl-choline receptors (AChR). From the 10-15% of the remaining patients, 45-50% are positive for Muscle Specific Tyrosine Kinase-Antibody (MuSK-Ab). It is believed that the thymus has a critical role in the pathogenesis of the disease with AChR-Ab, specially in patients with thymic abnormalities. In contrast, the role of thymus gland in MG with anti-MuSK-Ab is not clearly obvious. Patients with this antibody virtually have normal or only minimal follicular hyperplastic thymus. The presence of anti-MuSK Ab in a thymolipomatous (an uncommon tumor of thymus) MG is an atypical and new finding of MG because of not only thymolipoma but the presence of anti-MuSK antibodies which makes this case different from the previous reports of the antibodies-associated MG. Here, we present a young woman with thymolipoma and MG (a very uncommon kind of tumor-associated MG) and high level of anti-MuSK-Ab.

Analysis of outcomes following surgical treatment of thymolipomatous myasthenia gravis: comparison with thymomatous and non-thymomatous myasthenia gravis

OBJECTIVES

Although significant improvement in myasthenic symptoms has been reported following the removal of thymolipomas, information on surgical outcomes among patients with thymolipomatous myasthenia gravis (MG) is limited.

METHODS

This was a retrospective review of patients who underwent extended thymectomy for treatment of MG.

RESULTS

From 1995 to 2010, 267 patients with MG underwent extended thymectomy, including 104 with thymomatous MG, 151 with non-thymomatous MG and 12 (4.4%) with thymolipoma. The mean duration of myasthenic symptoms before surgery was greatest in the thymolipomatous group (P < 0.001). The lowest mean age (36.1 years old, P < 0.001) and the lowest preoperative serum anti-acetylcholine receptor antibody titre (P = 0.015) occurred in the non-thymomatous group. More thymic and adipose tissue was removed from the thymolipomatous group compared with the non-thymomatous group (P < 0.001). Regarding surgical outcomes, the rate of stable remission was higher in the non-thymomatous (42.3%) and thymolipomatous (41.7%) groups compared with the thymomatous group (28.8%, P = 0.029). No instances of postoperative exacerbation of MG or tumour recurrence were noted during the postoperative follow-up of patients treated for thymolipoma.

CONCLUSIONS

Our results suggest that patients with myasthenia thymolipomatous have surgical outcomes similar to those of patients with non-thymomatous MG and have a mean age at the time of surgery similar to that of patients with thymomatous MG.

Prolactin may be a promising therapeutic target for myasthenia gravis: hypothesis and importance

Myasthenia gravis (MG) is an autoimmune disease that affects the transmission signals from nerves to muscles. The basic pathology is the production of anti-acetylcholine receptor (AChR) antibodies (AChRAb) which is the consequence for the generation of autoreactive T lymphocytes responsing to AChR. However, the molecular mechanism of MG and the production of autoreactive T lymphocytes remain elusive. Recently beside its pivotal role in reproduction, the pituitary hormone prolactin (PRL) has been attributed to an immunomodulatory function. Furthermore it has been shown to be expressed in T cells and conversely it also affects the function of T cells, such as directly stimulating the proliferation and survival of T lymphocytes. In addition, elevated PRL levels frequently are described in autoimmune diseases, such as systemic lupus erythematosus (SLE) and multiple sclerosis (MS). So we hypothesized that the stimulating effect of PRL on T-cells function may be implied in the pathogenesis of MG and, perhaps, prolactin may be a promising therapeutic target for MG.