AUTOSOMAL RECESSIVE, FATAL INFANTILE HYPERTONIC MUSCULAR-DYSTROPHY AMONG CANADIAN NATIVES

We describe eleven mid-western Canadian aboriginal infants with a uniq ue, progressive muscle disorder. All except one had muscle biopsy and/ or autopsy. The infants were normal newborns who rapidly developed rig idity of all skeletal muscles, with early, respiratory insufficiency. Death occurred before 18 months of age. Electromyography showed increa sed insertion activity and profuse fibrillation potentials; motor unit potentials and interference pattern are normal until late in the cour se. Pathologic features include progressive, granular to powdery Z-ban d transformation, myofibrillar loss, and muscle regeneration. SDS-gel electrophoresis of one muscle sample revealed increased 54kDa and redu ced 80kDa protein fractions. This disease differs from other condition s with Z-band alterations because of continuous muscle activity and re lentless clinical progression. The clinical features, elevated serum c reatine kinase, electromyographic and muscle biopsy findings suggest a dystrophic process. The recognition of this condition as an autosomal recessive disorder allows appropriate genetic counselling.