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Autosomal recessive, fatal infantile hypertonic muscular dystrophy among Canadian Natives
A G Lacson1, S S Seshia, H B Sarnat
1Department of Pathology, University of Manitoba.
Insights
This study identifies a rare, fatal congenital muscle disorder in Canadian aboriginal infants characterized by muscle rigidity and respiratory failure. Autosomal recessive inheritance is suggested, aiding genetic counseling for this unique progressive myopathy.
Area of Science:
- Neurology
- Genetics
- Pediatrics
Background:
- Describes a unique, progressive muscle disorder observed in eleven mid-western Canadian aboriginal infants.
- Highlights the rapid onset of skeletal muscle rigidity and respiratory insufficiency in affected newborns.
Observation:
- Infants presented as normal at birth, rapidly developing generalized muscle rigidity.
- Clinical course was fatal, with death occurring before 18 months of age.
- Electromyography revealed increased insertion activity and fibrillation potentials, with normal motor unit potentials until late stages.
Findings:
- Muscle biopsies and autopsies showed progressive Z-band alteration (granular to powdery transformation), myofibrillar loss, and muscle regeneration.
- SDS-gel electrophoresis indicated alterations in specific protein fractions (increased 54kDa, reduced 80kDa).
- The condition presents distinct features from other Z-band alteration disorders due to continuous muscle activity and relentless progression.
Implications:
- The clinical and pathological findings suggest a novel dystrophic process.
- Recognition as an autosomal recessive disorder is crucial for accurate genetic counseling.
- This research contributes to understanding rare pediatric neuromuscular diseases and their genetic basis.
Abstract:
We describe eleven mid-western Canadian aboriginal infants with a unique, progressive muscle disorder. All except one had muscle biopsy and/or autopsy. The infants were normal newborns who rapidly developed rigidity of all skeletal muscles, with early, respiratory insufficiency. Death occurred before 18 months of age. Electromyography showed increased insertion activity and profuse fibrillation potentials; motor unit potentials and interference pattern are normal until late in the course. Pathologic features include progressive, granular to powdery Z-band transformation, myofibrillar loss, and muscle regeneration. SDS-gel electrophoresis of one muscle sample revealed increased 54kDa and reduced 80kDa protein fractions. This disease differs from other conditions with Z-band alterations because of continuous muscle activity and relentless clinical progression. The clinical features, elevated serum creatine kinase, electromyographic and muscle biopsy findings suggest a dystrophic process. The recognition of this condition as an autosomal recessive disorder allows appropriate genetic counselling.