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Limb girdle myasthenia: a study of familial and sporadic cases
A Vasant1, A B Taly, H Sathynarayanaswamy
1Department of Neurology, National Institute of Mental Health and Neuro Sciences, Bangalore.
Abstract:
Chronic limb girdle myasthenia gravis (MG) is a rare entity. We describe six such patients (F:M 4:2) who constituted 5% of 120 MG cases in a seven year study. The disease was familial in four and sporadic in two. No patient had ocular muscle weakness either at presentation (mean of 18.2 months after onset of illness) or during a mean follow up period of 36 months. Diagnosis was established by a positive decremental response on repetitive stimulation of a proximal muscle. Muscle biopsy was essentially normal in all five patients. All patients responded to acetylcholinesterase inhibitors, although to varying degrees. Four patients also received steroids. One patient with sporadic MG had transient worsening but others showed partial improvement. It is noteworthy that the initial diagnosis in these patient was other than MG. Diagnosis of limb girdle myasthenia needs to have a strong index of suspicion as it has therapeutic implications.
Insights
Chronic limb girdle myasthenia gravis (MG) is a rare neuromuscular disorder. Early diagnosis and treatment with acetylcholinesterase inhibitors can lead to partial improvement in affected patients.
Area of Science:
- Neurology
- Clinical Medicine
Background:
- Chronic limb girdle myasthenia gravis (MG) is an uncommon subtype of myasthenia gravis.
- This study investigates the characteristics and outcomes of six patients with this rare condition.
Observation:
- No ocular muscle weakness was observed at presentation or during follow-up in any of the six patients.
- The mean duration of illness before diagnosis was 18.2 months.
- Muscle biopsies were normal in five patients.
Findings:
- A positive decremental response on repetitive nerve stimulation of proximal muscles confirmed the diagnosis.
- All patients showed some response to acetylcholinesterase inhibitors, with four also receiving steroids.
- Four patients had familial disease, while two had sporadic cases.
Implications:
- Limb girdle myasthenia gravis requires a high index of suspicion for accurate diagnosis.
- Timely diagnosis has significant therapeutic implications, improving patient outcomes.
- This condition may initially be misdiagnosed, highlighting the need for specific diagnostic criteria.