Familial autoimmune MuSK positive myasthenia gravis

Journal of Neurology -     

Familial autoimmune myasthenia gravis with different pathogenetic antibodies.

Two cases of familial myasthenia gravis are reported. One patient is a typical case of autoimmune myasthenia with positive anti acetylcholine receptor antibodies, while in the second patient the impairment of neuromuscular transmission is likely to be due to antibodies directed against determinants other than the acetylcholine receptors.     

Familial myasthenia gravis.

A family is reported in which myasthenia gravis and thyroid disease occur over three generations. The grandmother and granddaughter have ocular myasthenia and an aunt in the second generation had generalised myasthenia gravis with a thymoma. The pattern of histocompatibility antigens (HLA) haplotypes, anti-AChR antibodies, anti-striate muscle antibodies and thyroid disease is described. The haplotype HLA-A1, B8 was found in affected members of the first and third generation but the family study showed that this was not the same haplotype because the HLA-A1, B8 haplotype in the third generation was contributed by an unaffected person marrying into the family in the second generation.     

Familial myasthenia gravis: report of 2 brothers

The familial form of myasthenia gravis is a relatively rare condition, occurring in about 3.4 per cent of myasthenic patients. Two familial cases with ocular myasthenia gravis are reported. They had a third brother who died probably with the same disease. Their parents are cousins. The authors made a brief approach of genetic, clinical, statistical and therapeutic aspects of the disease.     

Familial autoimmune myasthenia gravis and thymoma: occurrence in two brothers

At ages 31 and 42 years, two brothers presented with clinical, pharmacologic, electrophysiologic, and immunologic characteristics of autoimmune myasthenia gravis. At thymectomy, both had histologic findings of epithelial thymoma. HLA analysis revealed A2, A3, B7, and B39 antigens in one patient and A3, A24, B7, and B40 antigens in the other. Familial myasthenia gravis with thymoma has not been described previously. Familial thymoma has been rarely reported, but never with myasthenia gravis.     

Experimental autoimmune myasthenia gravis.

Injection of animals with purified acetylcholine receptor in complete Freund's adjuvant causes development of antibodies which crossreact with receptors in muscle. The crossreacting antibodies impair neuromuscular transmission. Animals with experimental autoimmune myasthenia gravis (EAMG) are excellent models for studying the complex mechanisms by which the autoimmune response to receptor in myasthenia gravis causes muscle weakness. This review first briefly describes the discovery of EAMG. Then, to provide the necessary perspective, receptor structure and function and properties of anti-receptor antibodies are discussed, followed by a brief review of the pathological mechanisms in EAMG.     

Familial autoimmune myastenia gravis: four patients involving three generations

BACKGROUND: Familial autoimmune myasthenia gravis (MG) is rare, although a genetic role for the development of autoimmune MG is suggested by concordance in monozygotic twins and the increased frequency of other autoimmune diseases in family members of myasthenics. METHODS: A patient with a family history of MG was evaluated in hospital. Relatives were interviewed and medical records examined for details regarding the diagnosis of MG in three other family members. RESULTS: The index case first experienced symptoms of MG at age 75 years. She developed generalized MG and required corticosteroids and immunosuppressive therapy to control her disease. Her father developed predominantly bulbar symptoms of MG at age 75 years. He died of complications experienced following a gastrostomy placed for continued difficulty swallowing. His brother developed similar symptoms of MG in his early 60s and died shortly after thymectomy. A 46-year-old nephew of the index case is also beginning to exhibit signs of generalized MG. Acetylcholine receptor antibodies were strongly positive in the index case and her nephew. (The assay was not available for her father and uncle). CONCLUSIONS: Four individuals in three successive generations had diagnoses of autoimmune MG. Study of familial cases such as these may clarify the contribution of genetic factors to the development of this disease.     

Familial myasthenia gravis: a case report in identical twins

To the best of our knowledge this is the seventh case report of monozygotic twins both affected by myasthenia gravis (MG). The monozygotism was proven by sex identity, blood group and HLA determinations ('O' Rh+, A2, A19.2, B40, CW3). One paternal aunt was also affected and the three cases have high titles of anti-acetylcholine receptor antibodies and anti-striated muscle antibodies, which indicate an acquired form of MG. After several myasthenic crises the twins are now doing well with corticosteroid therapy. The paternal aunt has a more benign form of MG, with ocular and limb involvement (grade IIa of Osserman) and was submitted to thymectomy. The authors discuss the use of corticosteroid for the infantile form of MG instead of thymectomy, based on the immaturity of the immune system in the young age. The use of other immunosuppressive drugs is not advisable because of potential hazardous development of neoplasms.     

Morphologic and immunologic studies in experimental autoimmune myasthenia gravis and myasthenia gravis.

An indirect immunoperoxidase technique was used to study by light microscopy the binding of serum from experimental autoimmune myasthenia gravis (EAMG) rabbits to junctionally and extrajunctionally located acetylcholine receptors (AChRs) in human and rat muscles. Binding was restricted to junctional AChR. Alpha bungarotoxin (a-BGT) partially blocked the binding of EAMG serum, while myasthenia gravis serum, carbamylcholine, decamethonium, and tubocurarine did not. A radioimmunoassay showed significant binding of antibodies in EAMG sera to 125l AChR. This binding was not inhibited by a-BGT, nor by carbamylcholine, decamethonium, or tubocurarine. Sera from 10 myasthenia gravis patients did not contain antibodies binding to the 125l AChR. We suggest that EAMG in rabbits induced by Torpedo AChR differs serologically from myasthenia gravis in patients, probably owing to antigenic differences between Torpedo and human AChR, and that antigenic differences also exist between junctional and extrajunctional receptors.     

Experimental autoimmune myasthenia gravis in the rat: A preliminary report

In chronic experimental myasthenia gravis (EAMG) in rat, the decrement of electrical and mechanical responses evoked by maximal repetitive (3–167/sec) stimuli to the nerve was greater in the slow-twitch soleus (SOL) than in the fast-twitch extensor digitorum longus (EDL) muscle. Excitation-contraction coupling was impaired in moderate to severe EAMG, as evidenced by a diminished staircase phenomenon and by diminished posttetanic potentiation (PTP) of twitch tension in two EDLs. The only morphologic abnormality observed was an increase in length of the endplates in the EDLs of those animals that had had an acute phase of EAMG. The latter had more than a 90% reduction in the amplitude of the action potential and in the twitch tension of the EDL when stimuli were applied to the nerve. Stimuli applied directly to the muscle evoked a tetanic tension that was one-third of normal. The staircase and PTP were normal. Necrosis occurred in the endplate and in the adjacent segment of muscle fiber; outside the endplate region, the muscle fiber was normal.     

Treatment of autoimmune myasthenia gravis

Autoimmune myasthenia gravis (MG) is associated with antibodies directed against the nicotinic acetylcholine receptor (AChR) in 85% of patients. Other postsynaptic neuromuscular junction antigens are implicated, e.g., muscle-specific receptor tyrosine kinase (MuSK), in a number of the remaining 15% of patients, so-called seronegative MG. The autoimmune attack generally leads to decreased concentrations of the AChR and damage to the structure of the endplate itself. This information has guided the empiric treatment of patients with MG and has suggested new treatment strategies. Whereas the outcome of patients with MG has improved because of more effective symptomatic treatment, including advances in critical care medicine and the use of cholinesterase inhibitors, the greatest advances have come from therapies that directly reduce the autoimmune attack or modify its effects on the AChR and the surrounding endplate. Immune-directed treatment of patients with MG, which is guided by this information and by data from the management of other autoimmune disease, is aimed at inducing an immunologic remission and then maintaining that remission. Remission induction is usually accomplished through the use of high-dose corticosteroids, frequently in conjunction with IV immunoglobulin or plasmapheresis. Maintenance of the remission is usually accomplished by slow tapering of the corticosteroids along with the use of "steroid-sparing" agents, which include azathioprine, thymectomy, and possibly mycophenolate. Therapy usually begins with cholinesterase inhibitors. If necessary, immune-directed treatment is added, beginning with either thymectomy or high-dose corticosteroids. The short-term therapies, i.e., IV immunoglobulin or plasmapheresis, may be effective in the early stages of treatment or later during an exacerbation. Steroid-sparing medications are usually added to facilitate the tapering phase.     

Neonatal experimental autoimmune myasthenia gravis

Neonatal rats born of and nursed by mothers immunized with Torpedo acetylcholine receptor protein developed a defect of neuromuscular transmission as indicated by reduced miniature endplate potential amplitudes. It is likely that antibodies to the Torpedo receptor protein were passively transferred to the neonates in the milk. With the exception of the route of transfer, this neonatal form of experimental autoimmune myasthenia gravis appears to be similar to its human counterpart, and thus can serve as an experimental model.     

重症肌无力合并自身免疫病的临床研究

目的分析重症肌无力(MG)合并自身免疫病的种类、发病年龄和临床特点。方法回顾性分析作者医院2008-01-2012-01住院的MG患者,包括合并自身免疫病的MG患者的临床资料、影像学及实验室检查资料及治疗记录。结果共收集MG患者305例,合并自身免疫病1种或1种以上者28例(9.18%),其中男9例、女19例,性别构成与非合并免疫病者无统计学差异(P>0.05)。自身免疫病在MG之前发病者12例,平均(69.6±35.3)个月;在MG发病之后者14例,平均(72.4±38.4)个月;与MG同时发现2例;(1)MG合并自身免疫病组的MG发病年龄为(33.9±9.4)岁,与非合并自身免疫病患者的MG发病年龄〔(35.3±12.2)岁〕无统计学差异(P>0.05)。合并甲状腺功能亢进(甲亢)患者MG发病年龄(27.4±12.5)岁,较合并其他自身免疫病患者的MG发病年龄〔(41.6±10.3)岁〕和非合并自身免疫病患者(35.3±12.2岁)均低(均P<0.05)。(2)合并的自身免疫病中属甲亢最多(13例),其次为类风湿性关节炎(5例)、桥本甲状腺炎(4例)、吉兰-巴雷综合征(3例)。其中有3例合并2种自身免疫病,1例合并3种自身免疫病。(3)合并自身免疫病MG患者的Osserman分型:发病初期Ⅰ型13例,Ⅱa型3例,Ⅱb型10例,Ⅲ型2例;其中MG合并甲亢患者以Ⅰ型发病10例,超过合并其他自身免疫病MG患者(P<0.05)。结论 MG可合并多种神经系统或全身自身免疫病,以甲亢最多见。合并甲亢的MG患者中MG发病年龄较轻,以眼肌型多见。自身免疫病可在MG发病前、后或同时期出现。     

Treatment of acquired autoimmune myasthenia gravis: a topic review.

We propose a new approach to staging the disease based on clinical and immunological response to treatment. We oppose clinical remission to immunological remission and define total clinical remission as the goal of therapy. We describe the use, side effects and indications of established therapies. Acetylcholine esterase inhibitors are only a symptomatic treatment as is plasma exchange. Usefulness and limits of thymectomy, corticosteroids and immunosuppressants are described here. Their goal is to reduce the auto-immune process. Long-term hazards from these medications are described and methods to reduce their potential risks are suggested. We suggest the number of patients having life threatening complications while undergoing aggressive immunosuppression can be reduced by a systematic approach to follow-up. In the second part of this review article, adapting management to specific situations is emphasized in refractory disease, respiratory failure, neonatal and juvenile forms of the disease. The special situation of seronegative myasthenia is discussed.     

Distal myasthenia gravis: case report

We report the case of a 30-year-old woman with a 7-year history of distal lower limbs weakness that evolved to upper limbs weakness. On neurological examination, she presented normal cranial nerves, bilateral quadriceps and feet interosseous atrophy, normal muscular tonus, muscular weakness more severe in dorsal feet interosseous and anterior tibial, and decreased deep tendon reflexes. Repetitive nerve stimulation of the ulnar and fibular nerves showed a decrement greater than 10% of the compound muscle action potential. Antibody against acetylcholine receptor titer was positive. Computed tomography scan of the thorax was normal. Thyroid function tests showed evidence of hyperthyroidism. Distal muscular weakness is a rare onset presentation of myasthenia gravis. However, myasthenia gravis must be considered in the differential diagnosis of distal limb weakness.