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.     

Myasthenia gravis as a prototype autoimmune receptor disease

We recorded full-field electroretinograms before and after vitrectomy in 18 eyes of 18 patients with idiopathic macular hole. The results were compared between affected and fellow eyes in the preoperative and early (within 10 days) and late (3 to 6 months) postoperative periods. No significant changes between affected and control eyes were found in the amplitude of the rod electroretinogram, mixed cone-rod electroretinogram, cone electroretinogram a- and b-waves or 30-Hz flicker electroretinogram in all stages of the study. The peak implicit times of the cone electroretinogram (a- and b-wave) and dark- and light- adapted oscillatory potential (O1-O4), however, were delayed. Also, the amplitude of the oscillatory potentials (O1+O2+O3+O4) was significantly reduced in the early postoperative period. By the late period, all of these changes had resolved. We concluded that electrophysiologic changes were derived from a transitory dysfunction of the inner retina. The possible causes of the electroretinographic changes would include mechanical trauma of the surgery, intravitreous air tamponade or the changes in vitreous electrolytes after surgery. Oscillatory potentials were more sensitive than a- and b-waves in eliciting dysfunction of the inner retina in operate on eyes.     

Primary respiratory failure as the presenting symptom in Lambert-Eaton myasthenic syndrome

Myasthenia gravis can present with rapid respiratory failure as the first manifestation of disease. In the Lambert-Eaton myasthenic syndrome (LEMS), such a manifestation has rarely been reported. We are reporting a patient who developed respiratory failure as the first manifestation of LEMS without associated carcinoma.     

Myasthenia gravis associated with small-cell carcinoma of the lung

A 49-year-old man complained of a 3-month history of progressive generalized muscle weakness. He was diagnosed as having small-cell lung carcinoma at the same time. He received an intravenous injection of edrophonium chloride with remarkable improvement of muscle strength. Electromyographic studies revealed a compound muscle action potential that decreased after repetitive stimulation. These findings were considered representative of myasthenia gravis (MG), and inconsistent with Eaton-Lambert syndrome. The appearance of MG with small-cell lung carcinoma seems to be very rare, but possible.     

Myasthenia gravis and primary squamous cell carcinoma of the thymus

Occurrence of primary squamous cell carcinoma of the thymus gland in a 65-year-old man with myasthenia gravis is reported. Histologic and immunohistochemical studies confirmed the diagnosis of a differentiated squamous cell carcinoma. Extensive clinical investigations ruled out another primary site for the tumor. The patient made a full recovery postoperatively. Only three cases of primary squamous cell carcinoma of the thymus gland in association with myasthenia gravis have been reported in the literature.     

Cervicofacial actinomycosis presenting as acute upper respiratory tract obstruction

An unusual case of cervicofacial actinomycosis presenting as acute upper airway obstruction and demanding urgent tracheostomy is reported. Diagnosis was established by microscopic examination of the pus and culture of Actinomyces israelii. Repeated surgical drainage of the purulent foci and prolonged treatment with penicillin obtained resolution of the disease. Clinicians dealing with acute head and neck swellings should always consider actinomycosis as a possible diagnosis.     

Hemochromatosis presenting as acute liver failure after iron supplementation

We present a case of eruptive collagenomas of the skin in a young girl. The typical clinical features and histology of this rare condition are described. The differential diagnosis and other types of cutaneous collagenomas are briefly discussed. A biopsy is required to confirm the excessive mature collagen which predominates in these lesions.     

Carotid artery dissections presenting as isolated posterior cerebral artery infarctions

Our purpose was to delineate the course of the ureter in the female pelvis in relationship to several important surgical landmarks. Ten female cadavers with undissected pelves were used. The ureter was identified at the pelvic brim and traced inferiorly to the bladder. Sets of measurements (+/- 0.1 cm) that help define the location of the ureter were obtained at the three landmarks; the ischial spine, the obturator canal and the insertion of the arcus tendineus on the pubic bone. The mean distances from the ureter to the pelvic floor were ischial spine, 3.2 +/- 0.1 cm; obturator canal, 3.2 +/- 0.1 cm; and the insertion of the arcus tendineus on the pubic bone, 1.6 +/- 0.1 cm. The mean distances from the arcus tendineus to the pelvic floor were ischial spine, 1.9 +/- 0.1 cm; obturator canal, 2.8 +/- 0.1 cm; and the insertion of the arcus tendineus on the pubic bone, 3.2 +/- 0.1 cm. This study defines the relationship of the ureter to the pelvic floor through measurements taken at three landmarks. The data should be useful to pelvic surgeons and are important for the development of future surgical techniques.     

Myasthenia gravis in old age. A retrospective study of 58 patients

The course in 58 cases of myasthenia gravis in subjects over 50 years of age is reported. They total about 30% of cases in all age-groups. 36.2% of the patients died after an average period of illness of 3.4 years. 58.6% initially showed only ocular symptoms and in 58.8% of these the myasthenia was likewise located only in the eyes in the further course of the illness. The prognosis of ocular myasthenia is very good if the myasthenic process does not extend to other muscle groups in the first or second year of illness. 41.2% of primary ocular myasthenia turned into other types, in most cases a generalized type, and these had a poor prognosis. 69.2% of these patients died after an average period of illness of 1.5 years due to myasthenia-induced complications. Cases of myasthenia which initially are of the generalized type, in which the average duration is only 2.7 years until death, and to some extent the bulbar types, also have a poor prognosis. Ocular myasthenic cases generally need only small doses of cholinesterase inhibitors. Some patients had no medical treatment because there was no subjective or objective need for it. Several patients were given doses of cholinesterase inhibitors which were too large; excessive doses are to be avoided because of the proven negative influence of cholinesterase inhibitors on the myoneural system. It is recommended that types of myasthenia with a poor prognosis be treated early with corticoids, ACTH or azathioprin, if the cholinesterase inhibitors have proved ineffective or it their effect is unsatisfactory. Thymectomy is advisable only in patients under 60 years of age.     

Myasthenia gravis: recognition of a human autoantigen at the molecular level

The symptoms of myasthenia gravis are primarily or exclusively due to an autoimmune response against the muscle nicotinic acetylcholine receptor (AChR) and this has been the object of intensive investigations for almost 20 years. A detailed picture at the molecular level of the interaction of this autoantigen with the key elements involved in the autoimmune response, such as anti-AChR antibodies, the T-cell receptor and restricting major histocompatibility complex molecules, is now emerging for both human myasthenia gravis and its experimental model, experimental autoimmune myasthenia gravis. Here, Maria Pia Protti and colleagues focus on the molecular interactions occurring in human myasthenia gravis and summarize recent information on pathogenic mechanisms of the autoimmune response, and the structure of epitopes recognized by B cells and CD4+ T cells of myasthenic patients on the AChR molecule.     

Myasthenia gravis: another autoimmune disease associated with hepatitis C virus infection

We report on a male Egyptian patient who developed myasthenia gravis with typical symptoms, beneficial response to pyridostigmine, and the presence of anti-acetylcholine receptor antibodies and anti-striated muscle antibodies during the course of a chronic hepatitis C infection complicated by liver cirrhosis. As also reported for the herpes simplex and for the HIV virus, hepatitis C may lead to myasthenia gravis via a mechanism of cross-reactivity between viral epitopes and the acetylcholine receptor.     

Adult respiratory failure

Pulmonary complications following thoracic surgery are common and associated with significant morbidity and mortality. In particular, acute respiratory distress syndrome (ARDS) can occur postoperatively or after trauma. This syndrome, when complicated by multisystem organ failure, often leads to a poor outcome. This article describes the etiology and pathophysiology of ARDS and evaluates recent advances in pharmacological and nonpharmacological therapies. In addition, newer modalities of mechanical ventilatory support are reviewed.     

Ataxia with isolated vitamin E deficiency presenting as mutation negative Friedreich''s ataxia

Ataxia with vitamin E deficiency is an autosomal recessive condition associated with a defect in the a-tocopherol transfer protein. Clinically it manifests as a progressive ataxia with a phenotype resembling that of Friedreich's ataxia. There is some evidence that progression of neurological symptoms is prevented by vitamin E therapy. A patient is described who was given a clinical diagnosis of Friedreich's ataxia. Molecular genetic analysis showed the absence of the frataxin gene expansion. Subsequent vitamin E assay showed deficiency and a diagnosis of ataxia with vitamin E deficiency was made. It is recommended that all patients with ataxia of unknown cause should have vitamin E deficiency excluded. When a diagnosis of Friedreich's ataxia is considered patients should have frataxin analysis in addition. Further, neurologists should be aware that ataxia with vitamin E deficiency may present as "mutation negative" Friedreich's ataxia.