Diseases of the neuromuscular junction are a heterogeneous group of disorders responsible for dysfunction of neuromuscular transmission, characterized by muscle weakness accentuated or improved by effort, depending on whether the disorders are located before or after the synapse³⁾. Autoimmune myasthenia is the most common disorder of the neuromuscular junction²⁾. It is due to a block in postsynaptic neuromuscular transmission by specific autoantibodies. Its clinical presentation is highly heterogeneous and variable, depending on the different muscle territories affected. The severity of the disease depends on whether the muscles involved in swallowing and/or breathing are affected, leading to acute respiratory failure⁴⁾. The average global incidence is 5.3 per million person-years²⁾. In sub-Saharan Africa, autoimmune myasthenia is characterized by long delays in diagnosis, reaching an average of 24 months in Senegal¹³⁾, difficulties in accessing diagnostic tools, and a greater frequency of severe forms⁷⁾. Some comparative studies in the USA¹⁰⁾ and South Africa⁵⁾, and some systematic reviews^2,6) have reported a higher frequency of early-onset forms, a greater predominance of females and a tendency toward more severe forms of the disease in patients of Black African origin compared with those of mainly European origin. However, few studies have been published on myasthenia in Togo^8,9). These observations led us to conduct the present study, the main objective of which is to describe the clinical, therapeutic, and evolutionary characteristics of myasthenia in the teaching hospitals of Lomé.

Our study took place from 1 January 2018 to 31 December 2023 in the neurology departments of the two University Hospitals of Lomé. It was a descriptive study with retrospective data collection with the agreement of the ethics committee. All patients seen in neurology outpatient clinics in the two university hospitals during the study period with myasthenia whose diagnoses were confirmed by pharmacological testing, anti-acetylcholine receptor antibody assays and/or electroneuromyography were included.

During the study period, the neurology departments of the two university hospitals consulted 36,733 patients. Of these patients, 14 were diagnosed with myasthenia, which represents 0.04% of consultations. The annual average of new cases of myasthenia is 2.33 cases per year. Women predominated, with a sex ratio (M/F) of 0.167 and an average age at onset of 24 ± 16.98 years. The mean time between the first sign of the disease and diagnosis was 29 ± 44.24 months, with extremes of 1 and 132 months. The 30-40 and 10-20 age groups were the most represented with 4 (28.57%) patients. The age group most represented in our series was 10- to 20-year-olds (35.71%). The clinical presentation at first contact was multisymptomatic in 9 (64.3%), whereas it was monosymptomatic in 5 (35.7%) patients, particularly ocular, with diplopia as the predominant clinical manifestation in 85.71% of cases. Juvenile myasthenia in patients under 15 years of age accounted for 35.71%, 8 (57.14%) patients had myasthenia in young adults (under 40 years of age) and 1 (7.14%) patient had myasthenia in elderly subjects occurring after the age of 40. In addition, 9 (64.26%) patients had generalized myasthenia with respiratory involvement in 5 (35.71%) patients. In our series, the Prostigmine test was performed in 13 (92.86%) patients, and was positive in 100% of cases. However, the anti-acetylcholine receptor antibody was tested in 9 (64.29%) patients and was positive in 6 (66.67%). Electroneuromyogram was performed in 11/14 (78.57%) patients, and a decrement was observed in 9/11 of these 11 patients (81.82%). Chest computed tomography (CT) scans were performed in 8/14 (57.14%) patients, and a thymoma was identified in 1/8 of these 8 patients (12.5%). All patients were treated with the anticholinesterase bromide pyridostigmine (Mestinon^®), administered orally in gradually increasing doses until a minimum effective dose of 360 mg/d was reached, 1 (7.14%) was treated with an anticholinesterase in combination with a corticosteroid and 1 (7.14%) was treated with a combination of an anticholinesterase and an immunosuppressant. All patients received a list of prohibited drugs. Thymectomy was not performed in any of the patients in our study. Eight (57.14%) patients reported a net clinical improvement with treatment. Three (21.43%) patients presented a myasthenic crisis requiring a stay in intensive care and 3 (21.43%) patients were lost to follow-up. Table 1 summarizes the data and in Table 2 the the characteristics of the patients.

It would be illusory to consider our study as representative of myasthenia in Togo. In fact, the retrospective nature of the study limits its scope because of the difficulties of keeping medical records in an underdeveloped country. In addition, not all of our patients have undergone all of the complementary examinations, since the entire cost of care and paraclinical examinations has been borne by the patient since the adoption of the Bamako initiative¹²⁾. The need to control healthcare expenditure since the end of the 1980s has prompted several African countries, including Togo, to adopt a healthcare policy based on cost recovery, with the use of generic drugs, with the population now having to pay for their healthcare. The limitation of the Bamako initiative is that the population concerned is extremely poor. This constituted a selection bias, limiting our myasthenic patient base to 14 patients. The hospital frequency in our study was 2.33 cases per year. This result is in agreement with that reported in a study by Razafindrasata et al.¹¹⁾ in Madagascar which found 16 cases over 8 years, or 2 cases per year. On the other hand, in Senegal the reported 18 cases over 4 years¹³⁾. Lompo et al.⁷⁾ in Burkina Faso reported 25 cases in 5 years 6 months, thus making 4.5 cases per year. This difference could be explained by the fact that our study was limited to only two health facilities, and did not include all the patients treated in the other centers. We noted a predominance of women, as reported in Niger⁴⁾ and Senegal¹³⁾. The majority of patients in our study were under 40 years of age, as in Burkina Faso⁷⁾ and Niger⁴⁾. The mean delay between the first sign of the disease and diagnosis was 29 ± 44.24 months, with extremes of 1 and 132 months in our study. These results were similar in Burkina Faso, where 26 months were reported⁷⁾. This delay in diagnosis is undoubtedly due to a lack of awareness of the signs of myasthenia gravis, especially when they are isolated and tilted, and particularly among general practitioners, given the relative rarity of the disease. In our context, the erratic diagnosis is attributable to the long course of treatment before the neurological consultation, which guarantees a diagnosis in less than a month. Diplopia was the most frequent initial manifestation in our series, as has also been reported in Algeria¹⁾. Generalized myasthenia was the most frequent in 64.29% of cases, with respiratory involvement in 35.71% of cases in our series. This finding was corroborated in Madagascar, where 37.5% of cases of severe generalized myasthenia gravis with respiratory involvement¹¹⁾ were reported, thus confirming a delay in diagnosis and management of this condition in Black Africa. Prostigmine testing has been positive in 100% of cases, as reported in Niger⁴⁾. This contrasts with other African series^1,5,7) where the positivity of the test varies from 70% to 90% and could be explained either by the size of our sample and probably by the recruitment bias of our patients. In addition, juvenile myasthenia gravis has been reported in 37.5% compared to 12% reported in Burkina Faso⁷⁾. This could be explained by a delay in diagnosis at a late, therefore severe, stage of the disease. Seronegative myasthenia represented 33.33% and these results were similar to those of Benabadji et al.¹⁾ and decrement was found in 81.82% of cases, as in Burkina Faso⁷⁾. Benabadji et al.¹⁾ in Algeria reported 34% of thymic pathology compared with 14.29% in our study. This difference can be explained by the cost of performing a thoracic CT scan. Anticholinesterase agents were used alone in the majority of cases in our study, or in combination in two cases, respectively with a corticosteroid and an immunosuppressant as reported in Madagascar¹¹⁾, unlike Djibo et al.⁴⁾ in Niger, where the combination of anticholinesterase agents and corticosteroids was predominant. Finally, in our study, the outcome was favorable in 64.29% of cases, with clinical remission and the onset of a myasthenic crisis in a quarter of cases, as reported in Niger⁴⁾ and Madagascar¹¹⁾. However, none of these authors^4,11) reported cases lost to follow-up, as was the case in 21.43% of cases in our study.

Myasthenia is a relatively rare but potentially fatal condition. It is legitimate to insist on improving the means of diagnosis and management through multicentre prospective studies in order to determine the best management strategies, adapted to our African realities.