Genetic localization of a newly recognized autosomal dominant limb-girdle muscular dystrophy with cardiac involvement (LGMD1B) to chromosome 1q11-21.

Limb-girdle muscular dystrophy (LGMD) constitutes a clinically and genetically heterogeneous group of myogenic disorders with a limb-girdle distribution of weakness. One autosomal dominant family, LGMD1A, has been linked to chromosome 5q, whereas in other autosomal dominant families linkage to this chromosome has been excluded. We studied 58 members of three families with a newly recognized autosomal dominantly inherited LGMD with cardiac involvement. A search with highly polymorphic microsatellite markers was carried out. The gene for this newly recognized dominant form of LGMD was located on chromosome 1q11-21, with a combined maximum two-point LOD score >12 at theta = 0.

A newly recognized autosomal dominant limb girdle muscular dystrophy with cardiac involvement.

Sixty-five members of three families with limb girdle muscular dystrophy (LGMD) underwent neurological, cardiological, and ancillary investigations. Thirty-five individuals were diagnosed as having slowly progressive autosomal dominant LGMD. Symmetrical weakness started in the proximal lower limb muscles, and gradually upper limb muscles also became affected. Early contractures of the spine were absent. Contractures of elbows and Achilles tendons were either minimal or late. Serum creatine kinase activity was normal to moderately elevated. Electromyogram and muscle biopsy were consistent with a mild muscular dystrophy. Cardiological abnormalities, found in more than one-half the patients, included dysrhythmias and atrioventricular (AV) conduction disturbances presenting as bradycardia, syncopal attacks necessitating pacemaker implantation, and sudden cardiac death. There was a significant relation between the severity of AV conduction disturbances and age. In nearly all patients, neuromuscular symptomatology preceded cardiological involvement. The early recognition of this previously not described, autosomal dominant LGMD with life-threatening cardiac involvement offers an opportunity for therapeutic intervention.