Penicillamine-induced myasthenia gravis in progressive systemic sclerosis

[Myasthenia, from the internist's point of view]

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.

Gold salts, D-penicillamine and allopurinol

Gold salts have been used in the treatment of patients with rheumatoid arthritis since 1927 [1]. After a controlled study, the Empire Rheumatism Council [2], confirmed the effectiveness of gold salts for the treatment of rheumatoid arthritis. Even today, chrysotherapy has remained one of the major therapeutic modalities in the second line treatment of progressive rheumatoid arthritis. Gold salts are also used in the treatment of pemphigus vulgaris [3] and bronchial asthma [4]. Before the introduction of an orally administered gold compound, auranofin (triethylphosphine gold tetra-acetyl glycopyranoside), to clinical use [5-7], parenterally administered gold salts, such as sodium aurothiomalate and gold thioglucose comprised chrysotherapy. The frequency and severity of the side effects for patients treated with parenteral gold versus those given oral gold preparations are significantly different [8-10]. With introduction of newer parental DMARDs, toxicity has been reduced using combination therapy [10a, 10b].

Myasthenia gravis

Adult-onset myasthenia gravis is an acquired autoimmune disorder of neuromuscular transmission in which acetylcholine receptor antibodies attack the postsynaptic membrane of the neuromuscular junction. Although the cause of this disease is unknown, the role of immune responses in its pathogenesis is well established. Circulating acetylcholine receptor antibodies are present in 80% to 90% of patients with the generalized form of myasthenia gravis. Most patients have ptosis, diplopia, dysarthria and dysphagia. The weakness and fatigue worsen on exertion and improve with rest. Respiratory muscle and limb weakness are rare at the onset of the disease. For the past two decades, there has been considerable progress in understanding the diagnosis and management of myasthenia gravis. The diagnosis is based on clinical presentation, neurologic examination, and confirmation by means of electrophysiologic testing and immunologic studies. Myasthenia gravis mimics many neuromuscular diseases and even illnesses such as depression and chronic fatigue syndrome. One should always exclude drug-induced myasthenia gravis for all patients. With the introduction of new modalities of treatment, particularly immunosuppressive or immunomodulating drugs, plasma exchange and thymectomy, the morbidity and mortality of myasthenia gravis have decreased dramatically to the point that myasthenia gravis should not be considered as serious a disease as it once was. Although the several therapeutic options are usually effective and have meant independence in daily life to many patients with myasthenia gravis, well-designed, controlled, prospective studies are still lacking.

D-penicillamine induced myasthenia gravis in rheumatoid arthritis: an unpredictable common occurrence?

Five patients out of 71 with rheumatoid arthritis (RA), who received D-penicillamine, developed myasthenia gravis (MG) within a two-year period. They all responded promptly to discontinuation of the drug and pyridostigmine administration. None of the patients had anti-Ro(SSA) antibodies or features of Sjögren's syndrome, whereas three of the five had the HLA-DR1 phenotype. The relatively high frequency of MG observed in our population, along with its unpredictability and potentially serious sequelae, necessitates its inclusion in the list of side effects of D-penicillamine routinely discussed with the patient, prior to initiation of the treatment. Full alertness of both the patient and the physician to even minor initial myasthenic symptoms, that dictate immediate discontinuation of the drug, is of obvious importance.

Ocular myasthenia: a protean disorder

Ocular myasthenia is a localized form of myasthenia clinically involving only the extraocular, levator palpebrae superioris, and/or orbicularis oculi muscles. Ocular manifestations can masquerade as a variety of ocular motility disorders, including cranial nerve and gaze palsies. A history of variable and fatiguable muscle weakness suggests this diagnosis, which may be confirmed by the edrophonium (Tensilon) test and acetylcholine receptor antibody titer. Anticholinesterases, corticosteroids and other immunosuppressive agents, and other therapeutic modalities, including thymectomy and plasmapheresis, are used in treatment. As the pathophysiology of myasthenia has been elucidated in recent years, newer treatment strategies have evolved, resulting in a much more favorable prognosis than several decades ago. This review provides historical background, pathophysiology, immuno-genetics, diagnostic testing, and treatment options for ocular myasthenia, as well as a discussion of drug-induced myasthenic syndromes.

[Scleroderma, thyroiditis, and myasthenia gravis: study of a case]

A thirty-six years old woman with myasthenia gravis developed cold intolerance after two years, and Hashimoto's thyroiditis diagnosis was established. Four years later she exhibited skin thickening (limited scleroderma). Laboratory and clinical findings suggested the CREST type of systemic sclerosis. Difficulty in scleroderma diagnosis is discussed, as overlap of syndromes. Hashimoto's thyroiditis and myasthenia gravis are infrequently associated. Occurrence of scleroderma and myasthenia gravis in the same patient is rare. The coincidence of these three disorders was not found in literature.

Augmented IgG anti-acetylcholine receptor response following chronic penicillamine administration

A model of D-penicillamine (DP) induced myasthenia gravis (MG) was developed in which the anti-acetylcholine receptor (anti-AChR) antibody response to AChR challenge was increased in mice chronically treated with DP. To investigate the mechanism of the DP induced increase, IgM and IgG anti-AChR responses to AChR challenge were studied. IgG responses were significantly greater in the DP treated mice than in the control group while IgM responses were not significantly different. This change appeared to be relatively specific for the AChR response because neither serum immunoglobulin levels nor the IgG response to a second antigen (purified protein derivative) were increased by DP treatment. These results suggest that a specific sensitization to AChR occurs during chronic DP treatment.

Molecular mechanisms of autoimmunity

Autoimmune diseases result from a combination of genetic susceptibility factors and exogenous influences such as infection or chemical (including drug) exposure. Germline DNA variations in genetic type as well as defects in antigen recognition acquired during thymic education of developing T-lymphocytes both contribute to impaired self: nonself discrimination and set the stage for later development of such diseases as myasthenia gravis, polymyositis, or systemic lupus erythematosus. In addition, drugs such as D-penicillamine, hydralazine, procainamide, or quinidine induce T-cell or B-cell changes which precipitate auto-reactivity and cause drug-induced disease. Intervention in autoimmune diseases with prednisone, alkylating agents or the future use of more selective monoclonal antibody reagents may be life-saving in some of these disorders.

D-penicillamine: chemistry and clinical use in rheumatic disease

The discovery of D-penicillamine and its uses in medicine are reviewed. Chemical-physical properties are discussed, and the molecular structure of D-penicillamine and several of its reaction products are illustrated. Examples of its three main types of biochemical reactions--sulfhydryl-disulfide exchange, thiazolidine formation, and metal chelation are included. Trials of D-penicillamine in RA patients are reviewed critically. The administration of the drug is discussed in detail, including dosages, clinical and laboratory responses, patterns of adverse side effects or toxicity, drug-induced autoimmune diseases, indications and contraindications, and the monitoring and management of patients.

Penicillamine-induced ocular myasthenia gravis

Two patients with rheumatoid arthritis (two women, 58 and 62 years old) developed reversible penicillamine-induced ocular myasthenia gravis. Both had the HLA-DR1 antigen, unlike most patients with idiopathic myasthenia gravis who show HLA-DR3, suggesting that penicillamine-induced myasthenia gravis and its idiopathic counterpart occur in patients with different genetic backgrounds. In both cases, cessation of drug treatment led to resolution of the symptoms.

[Myasthenia gravis induced by D-penicillamine in a patient with progressive systemic sclerosis]

The development of autoimmune diseases in some patients treated with D-penicillamine (DPA) suggests that the reported occurrence of a conduction disorder at the neuromuscular junction and the development of a reversible myasthenia gravis in rheumatoid disease, progressive systemic sclerosis or Wilson's disease after the use of DPA are part of a general predisposition for autoimmune disease related to DPA therapy. The case reported is an example. The DPA- induced myasthenia gravis (MG) is similar to the spontaneous MG clinically and electrophysiologically, though ocular signs prevail in the former. Antibodies to acetylcholine receptor have been demonstrated and thymic hyperplasia also has been formed. Regarding the onset of myasthenic manifestations the duration of the treatment with DPA varies from 6 to 10 months. The action of DPA on the neuromuscular junction is different from that occurring in spontaneous MG. The pathogenesis of the DPA induced MG is still obscure. The chemical properties of DPA permit it to react with many proteins and some alteration of proteins may appear, with structural changes in the composition and antigenicity of the collagen fibers. In vitro DPA causes disorder of acetylcholine receptor bridges to alpha, beta, gamma sub-units with reduction of the S-S bridges in the gamma-subunit. This decreases the linkage of high affinity and abolishes its positive cooperative system, reducing the S-S connection in the alpha-unit near the acetylcholine linkage. The interaction between DPA and receptor may induce antigenic alteration in this latter, starting the autoimmune phenomena. The other possibility is the stimulation of prostaglandin E-1 synthesis by DPA may fill the allosteric place of ACh receptor, interfering on the neuromuscular junction.

Augmented anti-acetylcholine receptor response following long-term penicillamine administration

Because of the association of D-penicillamine (DP) therapy with myasthenia gravis, we have studied long-term DP treatment in five inbred strains of mice with doses comparable to those used in patients with rheumatoid arthritis. No clinical weakness or anti-acetylcholine receptor (AChR) antibody developed with up to 6 months of treatment, but augmented responses did occur to challenge with purified AChR in adjuvant. Anti-AChR antibody titers in C57BL/6 and C3H/He mice were significantly higher after challenge with AChR in DP-treated than in control mice. Augmented anti-AChR titers were not seen in strain A mice, but after 6 months of DP treatment increased susceptibility developed to the induction of experimental autoimmune myasthenia gravis. Nine weeks after challenge with purified AChR, 10 of 11 mice developed clinical weakness, leading to death in 6. Results of edrophonium testing were positive in 5 of 6 mice, and electrophysiological abnormalities were demonstrated in 3 of the surviving mice. Long-term DP treatment is associated with augmented anti-AChR antibody responses in C3H/He and C57BL/6 mice, and increased susceptibility to experimental autoimmune myasthenia gravis in strain A mice.

Penicillamine-induced myasthenia in rheumatoid arthritis: its clinical and genetic features

The clinical features and genetic background of 18 patients with rheumatoid arthritis were investigated following the development of penicillamine-induced myasthenia (PIM). The initial myasthenia symptoms in all patients consisted of variable diplopia and/or ptosis with progression to a more generalized involvement in 7 of them. No clinical, humoral, or genetic factor was determined which would allow identification of individuals developing generalized as opposed to ocular myasthenia. Withdrawal of penicillamine was associated over 4-60 weeks with a slow resolution of symptoms, facilitated in 12 patients by the use of anticholinesterase agents. In 2 patients a persistent partial unilateral ptosis remains after 15 and 25 months, while in a further patient diplopia is present 42 months after resolution of the other myasthenic symptoms. The patients with PIM when compared with a healthy 'control' population had a significant increase in HLA Dr1 (p corr less than 0.005) and an absence of HLA Dr 3. A genetic susceptibility to the development of PIM, distinct from that observed in myasthenia gravis of spontaneous onset, is suggested by this abnormal distribution of HLA Dr antigens.

HLA antigens and acetylcholine receptor antibodies in penicillamine induced myasthenia gravis

Antibodies to the acetylcholine receptor and HLA antigens have been studied in patients with myasthenia gravis occurring in association with penicillamine treatment. The properties of the antiacetylcholine receptor in these patients differed from those in patients with idiopathic myasthenia gravis in terms of specificity and affinity. These patients had an increased prevalence of HLA Bw35 and DR1 compared to controls and a decreased frequency of B8 and DR3 compared to patients with idiopathic myasthenia gravis. Likewise, they had a decreased frequency of DR4 compared to patients with rheumatoid arthritis. These data provide supportive evidence for a role for penicillamine in the induction of myasthenia gravis in genetically predisposed individuals.

Thymic abnormalities: antigen or antibody? Response to thymectomy in myasthenia gravis

The therapeutic value of thymectomy for myasthenia is still questioned although it retains an important place among management modalities that strive for sustained remission. Questions derive from uncertainty as to appropriate timing, variable extent of resection and quantitation of response. Forty-seven patients, followed one to seven years, underwent an extended transsternal or combined transcervical-transsternal procedure with anterior mediastinal exenteration. Sixteen have been in complete remission from six months to six years, four are asymptomatic on occasional pyridostigmine and eight are significantly improved. Evaluation of thymic pathology (hyperplasic, involuted areas, and thymoma) included a search for thymic myoid cells by fluorescence cytochemistry. Antibodies to acetylcholine receptor present in 38 of 43, decreased post-operatively to normal in four, by 50% to 80% in 14, by 20 to 50% in three and were unchanged in 14. Most remissions occurred in young women with noninvoluted hyperplastic glands and variably high anti-AChR titers which dropped toward normal in seven of 15. These results encourage us to utilize this procedure routinely.