Radhakrishnan et al. (1988) conducted a retrospective study (January 1983 to December 1986) which included 24 patients (18 index cases) with spinal muscular atrophy (hereditary motor neuropathy, HMN), 9 with myasthenia gravis (MG), 6 with progressive supranuclear palsy (PSP), and 5 with subacute sclerosing panencephalitis (SSPE). The adjusted average incidence of MG was 4.4/million/year, 2.1 for males and 6.8 for females. The female:male incidence ratio was 3.2:1.
In 1996, El-Zunni et al. retrospectively studied 18 cases of MG (October 1991 to December 1994). The female to male ratio was 2.6:1 (13 females and five males). The mean age of presentation was 13.3 years later for male patients compared to females (mean age of presentation in females was 26.5 years and in males 39.8 years). The average time interval between the onset of symptoms and diagnosis was 2.5 years. At the time of diagnosis 94.5% (17 cases) of the cases had generalized MG and 5.5% (one case) had ocular symptoms only. In 11.1% (two cases) of patients an association with thyroid disorder was observed. Repetitive nerve stimulation (RNS) test was abnormal in 83% (15 cases) of the cases. All cases were initially treated with anticholinesterase and 22.2% (four cases) also additionally required steroid therapy. Thymectomy was performed on eight cases, four of which had thymus hyperplasia. None of the cases had any thymoma. Of these eight cases, one case (12.5%) had complete remission, five cases (62.5%) were doing well with a reduced dose of anticholinesterase and +/- steroids. However, two cases (25%) required intermittent plasmapharesis and immunosuppressants in addition to anticholinesterase and steroids.
Al-Four et al. (1995) reported a case of myasthenia gravis crisis in a 15-year-old boy admitted with acute respiratory distress. His symptoms were fever, cough, nasal regurgitation, and dysphagia, with a past history of easy fatigability and of a mild similar condition one year ago, for which no diagnosis was made. Clinically, he was conscious, distressed, restless, breathless, and febrile, with conjuntival congestion. His speech was with usual timbre and dysarthric mushy quality, pupils were equal and reactive to light, and all cranial nerves were intact. As his condition was deteriorating, intubation and intermittent positive pressure ventilation as well as chest physiotherapy were done. Investigations revealed normal chest X-ray (except for hilar haziness) and positive neostigmine test (edrophonium was unavailable). Electromyography was not done. The patient's muscle power improved and he was extubated as he was started on gradually increased doses of corticosteroid, immunosuppresants, and a cholinesterase inhibitor, as well as broad spectrum antibiotics. Thymectomy was planned to achieve long remission. The authors advised early and effective antibiotic therapy, respiratory assistance and physiotherapy as well as plasmaphoresis for patients in crisis. [Al-Four NS, Rizk MSE, Gilani SN, El-Bussieny HA, Mathew J. Myasthenia Gravis crisis. Oman Med J. 1995; 11(4):37-8.]
Koul et al. (1996) described eight patients (two males and six females) with myasthenia gravis seen over a period of five years. Their mean age of presentation was three years and 11 months. In five of the children, symptoms started when they were below the age of two years. Of these, four were diagnosed with congenital MG, based on their testing negative for acetylcholine receptor antibodies. These patients with CMG responded poorly to Pyridostigmine, and no progression in the disease course was noticed in two patients when followed up for two years. Corticosteoids and immunoglobulins did not improve the clinical condition of one child. Of the patients with CMG, two were siblings, and the father of one female patient, (who was found to have clinical and biochemical hyperthyroidism as well) had hyperthyroidism but no myasthenia gravis. Investigations conducted on all the patients included collagen workup (negative), electromyogram (decremental response in six), tensilon test (positive in all), and CT mediastinum (showed enlarged thymus in three out of six patients, two of which underwent thymectomy). As regards the treatment, three patients received immunoglobulins and four patients received corticosteroids, and only one from each group showed good response. On the other hand, only one child who developed myasthenic crisis received plasmapharesis (which was not useful), and Azathioprine. [Koul RL, Joshi RM, Raj AG, Alexander PC, Anil G, Al-Farsi B, El-Bualy M. Myasthenia Gravis in children in Oman. Oman Med J. 1996; 13(1):58-60.]
Dashora et al. (1999) reported an unusual presentation of myasthenia gravis as acute fulminant respiratory failure in a 14-year old Omani girl who presented with a three days history of fever and throat pain along with difficulty in swallowing and breathlessness at the day of presentation. She was febrile, in severe respiratory distress, normotensive, her throat was filled with secretions, and her chest had bilateral crepitations and ronchi. Neurologically, she was drowsy with bilateral drooping of eyelids with normal ocular movements, and there was no local neurological deficit. An initial diagnosis of respiratory infection was made, but then she developed respiratory arrest, for which she was intubated and mechanically ventilated. A diagnosis of myasthenia gravis was suspected in view of the bilateral ptosis and sudden respiratory distress, and she dramatically improved as she received a parasympathomimetic drug intramuscularly and was extubated on the same day. She was then referred to a tertiary hospital where she was found to have in addition to the bilateral ptosis, palatal weakness and easy fatigability of limbs. The diagnosis of myasthenia gravis was confirmed by a positive Tensilon test and strongly positive acetylcholine receptor antibodies in her serum. Chest x-ray and CT scan of the chest excluded the presence of thymic mass. Other investigations which included serum biochemistry, CK, and thyroid function test were normal. She was managed by intravenous immunoglobulin 400 mg/kg/day for five days along with parasympathomimetics and immunosuppressants, and upon discharge she was asymptomatic. [Dashora UK, Faid M, Titus MA, Bhat AR. Acute respiratory failure as the initial presentation of myasthenia gravis, a case report. Oman Med J. 1999; 15(3):53-4.]
Jacob et al. (2003) conducted a retrospective study over a period of 3 years on 50 patients (male: female ratio of 2:3) diagnosed with myasthenia gravis. Only six patients had purely ocular, while 44 had the generalized form. Bulbar involvement was seen in 28 patients. Four patients had coexisting diseases as well (one with thyrotoxicosis and three with hypothyroidism, while one with the ocular form had diabetes mellitus, and one had epilepsy). Ventilatory support was needed in 12 patients. Investigations done included Tensilon test (positive in all), and repetitive stimulation test (positive in all patients with the generalized disease). CT scan showed thymus hyperplasia in 10 patients. Anti-acetylcholine receptor antibodies were found in 80% of generalized patients and in 50 % of the ocular form. Immunoglobulins and plasmaphoresis were successfully used to treat myasthenic crises. Trans sternal thymectomy was done in 29 patients with good outcome, as only 10 patients required further immune suppression while the rest needed only pyridostigmine and nine had a drug free remission period of two years. Only one pregnancy (multigravida) out of eight deteriorated during the last trimester and was managed by immunoglobulins. All babies were born healthy and needed no support. Jacob et al. (2003) realized that both bulbar and ventilatory involvement were more in their series when compared to data from western societies.
Zachariah et al. (2004) reported a ten-year old girl with juvenile myasthenia gravis, who presented with a one-year history of drooping of her eyelids which started gradually and varied in severity, being more at the end of the day or when tired. There was no history of fever, seizure, difficulty in swallowing, chewing or talking, and she was not on any medications. All her family members were normal. Examination revealed no abnormality, but neurologically, there was severe ptosis of the right upper lid with restricted ocular movements except for adduction, while the left eye showed mild ptosis with limited upward eye movement, which increased upon sustaining an upward gaze. Both papillary reflexes were normal, and so were the anterior and posterior segments of both eyes. According to the above findings, myasthenia gravis was suspected, and was diagnosed by complete resolution of ptosis and ophthalmoplegia upon intramuscular injection of neostigmine (0.04 mg/kg). The diagnosis was confirmed upon detection of an abnormally elevated level of acetylcholine receptor antibody (5272.30 nmol/l). Chest X-ray showed no mediastinal widening while other serological investigations (ANA, TFT, and ESR) were normal. This patient was managed by a cholinesterase inhibitor (30mg six hourly) and she showed marked improvement in ptosis and ophthalmoplegia on follow up. [Zachariah G, Keshav BR, Idiculla T. Juvenile myasthenia gravis - a case report. Oman Med J. 2004; 19(2):58-9.]
Al-Moallem et al. (2008) undertook a retrospective study to clarify the clinical profile of MG in Arabs. A total of 104 patients diagnosed with MG in Saudi Arabia between 1984 and 2006 were included in the study. This included 40 males and 64 females, with an age at diagnosis ranging from 3 to 73 years. The mean age at diagnosis, at 22.5 years for females and 28.2 years for males, was lower than that reported for other racial groups. In addition, a second peak of onset after 50 years of age described in studies of other populations was not noticed in this study. Acetylcholine receptor antibodies were present in 73% of the patients for whom results were available. There were five seronegative patients with childhood-onset MG, of whom four had muscle biopsies done, ruling out the possibility of mitochondrial diseases and muscular dystrophies. More than half the patients had very mild to moderate form of the disease, while less than 2% were in crisis at the time of presentation. A quarter of the patients had other autoimmune diseases; the most common being thyroid disease, prompting the Al-Moallem et al. (2008) to suggest the possibility of a co-existing myopathy. Thymectomy was performed on 81 patients, and although the rate of complete stable remission between thymectomized and non-thymectomized patients was not significantly different, the achievement of any sort of remission was significantly higher in the thymectomized patients. Also, patients seronegative for acetylcholine receptor antibodies had better remission rates.
Hajeer et al. (2009) reported on the association of HLA classes I and II with Myasthenia Gravis (MG) in the Suadi population. One hundred and nine Saudi patients with MG (73 females and 36 males) and 383 healthy controls from the same ethnicity were included in the study. The MG patients had the characteristic signs and symptoms and features of MG. Only five patients had ocular MG and the rest presented with the generalized version of the disorder. Typing HLA for the two groups revealed a strong association in the case of HLA-B*08, and MG patients carrying the latter allele are mostly females with young age at onset. On the other hand, the results indicated that the most frequent allele in the Saudi population; HLA-B*50 has a protective effect in the context of MG. Interestingly, the latter allele is absent or rarely found in other populations.
